This specification defines the syntax and semantics of XSLT, which is
a
language for transforming XML documents into other XML documents.
XSLT is designed for use as part of XSL, which is a stylesheet
language
for XML. In addition to XSLT, XSL includes an XML vocabulary for
specifying
formatting. XSL specifies the styling of an XML document by using XSLT
to
describe how the document is transformed into another XML document that
uses
the formatting vocabulary.
XSLT is also designed to be used independently of XSL. However, XSLT
is
not intended as a completely general-purpose XML transformation
language.
Rather it is designed primarily for the kinds of transformations that
are
needed when XSLT is used as part of XSL.
This document has been reviewed by W3C Members and other interested
parties and has been endorsed by the Director as a W3C Recommendation.
It
is a stable document and may be used as reference material or cited as a
normative reference from other documents. W3C's role in making the
Recommendation is to draw attention to the specification and to promote
its
widespread deployment. This enhances the functionality and
interoperability
of the Web.
The list of known errors in this specification is available at http://www.w3.org/1999/11/REC-xslt-19991116-errata.
Comments on this specification may be sent to [email protected]; archives of
the
comments are available. Public discussion of XSL, including XSL
Transformations, takes place on the XSL-List
mailing list.
The English version of this specification is the only normative
version.
However, for translations of this document, see http://www.w3.org/Style/XSL/translations.html.
A list of current W3C Recommendations and other technical documents
can be
found at http://www.w3.org/TR.
This specification has been produced as part of the W3C Style activity.
1
Introduction
2
Stylesheet Structure
2.1
XSLT Namespace
2.2
Stylesheet
Element
2.3
Literal
Result Element as Stylesheet
2.4
Qualified Names
2.5
Forwards-Compatible
Processing
2.6
Combining
Stylesheets
2.6.1
Stylesheet
Inclusion
2.6.2
Stylesheet
Import
2.7
Embedding
Stylesheets
3
Data Model
3.1
Root Node
Children
3.2
Base URI
3.3
Unparsed
Entities
3.4
Whitespace Stripping
4
Expressions
5
Template Rules
5.1
Processing
Model
5.2
Patterns
5.3
Defining
Template Rules
5.4
Applying
Template Rules
5.5
Conflict Resolution for
Template Rules
5.6
Overriding Template
Rules
5.7
Modes
5.8
Built-in Template
Rules
6
Named Templates
7
Creating the Result Tree
7.1
Creating Elements and
Attributes
7.1.1
Literal Result Elements
7.1.2
Creating Elements
with
xsl:element
7.1.3
Creating Attributes with xsl:attribute
7.1.4
Named Attribute Sets
7.2
Creating
Text
7.3
Creating Processing
Instructions
7.4
Creating
Comments
7.5
Copying
7.6
Computing
Generated Text
7.6.1
Generating Text with xsl:value-of
7.6.2
Attribute Value Templates
7.7
Numbering
7.7.1
Number
to String Conversion Attributes
8
Repetition
9
Conditional Processing
9.1
Conditional
Processing
with xsl:if
9.2
Conditional
Processing
with xsl:choose
10
Sorting
11
Variables and Parameters
11.1
Result
Tree
Fragments
11.2
Values of
Variables
and Parameters
11.3
Using Values of
Variables and
Parameters with xsl:copy-of
11.4
Top-level
Variables and Parameters
11.5
Variables and
Parameters within Templates
11.6
Passing Parameters to
Templates
12
Additional Functions
12.1
Multiple Source
Documents
12.2
Keys
12.3
Number Formatting
12.4
Miscellaneous
Additional
Functions
13
Messages
14
Extensions
14.1
Extension
Elements
14.2
Extension
Functions
15
Fallback
16
Output
16.1
XML
Output
Method
16.2
HTML
Output Method
16.3
Text
Output Method
16.4
Disabling
Output
Escaping
17
Conformance
18
Notation
Appendices
A
References
A.1
Normative
References
A.2
Other
References
B
Element Syntax Summary
C
DTD Fragment for XSLT Stylesheets (Non-Normative)
D
Examples (Non-Normative)
D.1
Document
Example
D.2
Data Example
E
Acknowledgements
(Non-Normative)
F
Changes from
Proposed Recommendation (Non-Normative)
G
Features
under
Consideration for Future Versions of XSLT (Non-Normative)
1 Introduction
This specification defines the syntax and semantics of the XSLT
language.
A transformation in the XSLT language is expressed as a well-formed XML
document [XML] conforming to the Namespaces in XML
Recommendation [XML Names], which may include
both
elements that are defined by XSLT and elements that are not defined by
XSLT.
XSLT-defined elements are distinguished
by
belonging to a specific XML namespace (see [2.1
XSLT
Namespace]), which is referred to in this specification as the
XSLT namespace. Thus this specification is a definition of the
syntax
and semantics of the XSLT namespace.
A transformation expressed in XSLT describes rules for transforming a
source tree into a result tree. The transformation is achieved by
associating patterns with templates. A pattern is matched against
elements
in the source tree. A template is instantiated to create part of the
result
tree. The result tree is separate from the source tree. The structure
of
the result tree can be completely different from the structure of the
source
tree. In constructing the result tree, elements from the source tree can
be
filtered and reordered, and arbitrary structure can be added.
A transformation expressed in XSLT is called a stylesheet. This is
because, in the case when XSLT is transforming into the XSL formatting
vocabulary, the transformation functions as a stylesheet.
This document does not specify how an XSLT stylesheet is associated
with
an XML document. It is recommended that XSL processors support the
mechanism
described in [XML Stylesheet]. When this or any
other mechanism yields a sequence of more than one XSLT stylesheet to be
applied simultaneously to a XML document, then the effect should be the
same
as applying a single stylesheet that imports each member of the sequence
in
order (see [2.6.2 Stylesheet Import]).
A stylesheet contains a set of template rules. A template rule has
two
parts: a pattern which is matched against nodes in the source tree and a
template which can be instantiated to form part of the result tree.
This
allows a stylesheet to be applicable to a wide class of documents that
have
similar source tree structures.
A template is instantiated for a particular source element to create
part
of the result tree. A template can contain elements that specify literal
result element structure. A template can also contain elements from the
XSLT
namespace that are instructions for creating result tree fragments.
When a
template is instantiated, each instruction is executed and replaced by
the
result tree fragment that it creates. Instructions can select and
process
descendant source elements. Processing a descendant element creates a
result
tree fragment by finding the applicable template rule and instantiating
its
template. Note that elements are only processed when they have been
selected
by the execution of an instruction. The result tree is constructed by
finding the template rule for the root node and instantiating its
template.
In the process of finding the applicable template rule, more than one
template rule may have a pattern that matches a given element. However,
only
one template rule will be applied. The method for deciding which
template
rule to apply is described in [5.5 Conflict
Resolution
for Template Rules].
A single template by itself has considerable power: it can create
structures of arbitrary complexity; it can pull string values out of
arbitrary locations in the source tree; it can generate structures that
are
repeated according to the occurrence of elements in the source tree.
For
simple transformations where the structure of the result tree is
independent
of the structure of the source tree, a stylesheet can often consist of
only a
single template, which functions as a template for the complete result
tree.
Transformations on XML documents that represent data are often of this
kind
(see [D.2 Data Example]). XSLT allows
a
simplified syntax for such stylesheets (see [2.3 Literal Result Element as
Stylesheet]).
When a template is instantiated, it is always instantiated with
respect to
a current node and a current node list. The current
node is
always a member of the current node list. Many operations in XSLT are
relative to the current node. Only a few instructions change the current
node
list or the current node (see [5 Template Rules]
and [8 Repetition]); during the
instantiation
of one of these instructions, the current node list changes to a new
list of
nodes and each member of this new list becomes the current node in turn;
after the instantiation of the instruction is complete, the current node
and
current node list revert to what they were before the instruction was
instantiated.
XSLT makes use of the expression language defined by [XPath]
for selecting elements for processing, for
conditional processing and for generating text.
XSLT provides two "hooks" for extending the language, one hook for
extending the set of instruction elements used in templates and one hook
for
extending the set of functions used in XPath expressions. These hooks
are
both based on XML namespaces. This version of XSLT does not define a
mechanism for implementing the hooks. See [14
Extensions].
NOTE:The XSL WG intends to define such a mechanism in a future
version of this specification or in a separate specification.
The element syntax summary notation used to describe the syntax of
XSLT-defined elements is described in [18
Notation].
The MIME media types text/xml and
application/xml [RFC2376] should be
used
for XSLT stylesheets. It is possible that a media type will be
registered
specifically for XSLT stylesheets; if and when it is, that media type
may
also be used.
2 Stylesheet Structure
2.1 XSLT Namespace
The XSLT namespace has the URI
http://www.w3.org/1999/XSL/Transform.
NOTE:The 1999 in the URI indicates the year in
which
the URI was allocated by the W3C. It does not indicate the version of
XSLT
being used, which is specified by attributes (see [2.2 Stylesheet Element] and [2.3 Literal Result Element as
Stylesheet]).
XSLT processors must use the XML namespaces mechanism [XML Names] to recognize elements and attributes
from
this namespace. Elements from the XSLT namespace are recognized only in
the
stylesheet not in the source document. The complete list of XSLT-defined
elements is specified in [B Element
Syntax Summary]. Vendors must not extend the XSLT namespace
with
additional elements or attributes. Instead, any extension must be in a
separate namespace. Any namespace that is used for additional
instruction
elements must be identified by means of the extension element mechanism
specified in [14.1 Extension
Elements].
This specification uses a prefix of xsl: for referring
to
elements in the XSLT namespace. However, XSLT stylesheets are free to
use any
prefix, provided that there is a namespace declaration that binds the
prefix
to the URI of the XSLT namespace.
An element from the XSLT namespace may have any attribute not from
the
XSLT namespace, provided that the expanded-name of
the
attribute has a non-null namespace URI. The presence of such attributes
must
not change the behavior of XSLT elements and functions defined in this
document. Thus, an XSLT processor is always free to ignore such
attributes,
and must ignore such attributes without giving an error if it does not
recognize the namespace URI. Such attributes can provide, for example,
unique
identifiers, optimization hints, or documentation.
It is an error for an element from the XSLT namespace to have
attributes
with expanded-names that have null namespace URIs (i.e. attributes with
unprefixed names) other than attributes defined for the element in this
document.
NOTE:The conventions used for the names of XSLT elements,
attributes
and functions are that names are all lower-case, use hyphens to
separate
words, and use abbreviations only if they already appear in the syntax
of a
related language such as XML or HTML.
2.2 Stylesheet Element
<xsl:stylesheet
id = id
extension-element-prefixes = tokens
exclude-result-prefixes = tokens
version = number>
<!-- Content: (xsl:import*,
top-level-elements) -->
</xsl:stylesheet>
<xsl:transform
id = id
extension-element-prefixes = tokens
exclude-result-prefixes = tokens
version = number>
<!-- Content: (xsl:import*,
top-level-elements) -->
</xsl:transform>
A stylesheet is represented by an xsl:stylesheet element
in
an XML document. xsl:transform is allowed as a synonym for
xsl:stylesheet.
An xsl:stylesheet element must have a version
attribute, indicating the version of XSLT that the stylesheet requires.
For
this version of XSLT, the value should be 1.0. When the
value
is not equal to 1.0, forwards-compatible processing mode is
enabled (see [2.5 Forwards-Compatible
Processing]).
The xsl:stylesheet element may contain the following
types of
elements:
xsl:import
xsl:include
xsl:strip-space
xsl:preserve-space
xsl:output
xsl:key
xsl:decimal-format
xsl:namespace-alias
xsl:attribute-set
xsl:variable
xsl:param
xsl:template
An element occurring as a child of an
xsl:stylesheet element is called a top-level
element.
This example shows the structure of a stylesheet. Ellipses
(...) indicate where attribute values or content have been
omitted. Although this example shows one of each type of allowed
element,
stylesheets may contain zero or more of each of these elements.
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:import href="..."/>
<xsl:include href="..."/>
<xsl:strip-space elements="..."/>
<xsl:preserve-space elements="..."/>
<xsl:output method="..."/>
<xsl:key name="..." match="..." use="..."/>
<xsl:decimal-format name="..."/>
<xsl:namespace-alias stylesheet-prefix="..." result-prefix="..."/>
<xsl:attribute-set name="...">
...
</xsl:attribute-set>
<xsl:variable name="...">...</xsl:variable>
<xsl:param name="...">...</xsl:param>
<xsl:template match="...">
...
</xsl:template>
<xsl:template name="...">
...
</xsl:template>
</xsl:stylesheet>
The order in which the children of the xsl:stylesheet
element
occur is not significant except for xsl:import elements and
for
error recovery. Users are free to order the elements as they prefer,
and
stylesheet creation tools need not provide control over the order in
which
the elements occur.
In addition, the xsl:stylesheet element may contain any
element not from the XSLT namespace, provided that the expanded-name of
the
element has a non-null namespace URI. The presence of such top-level
elements must not change the behavior of XSLT elements and functions
defined
in this document; for example, it would not be permitted for such a
top-level
element to specify that xsl:apply-templates was to use
different
rules to resolve conflicts. Thus, an XSLT processor is always free to
ignore
such top-level elements, and must ignore a top-level element without
giving
an error if it does not recognize the namespace URI. Such elements can
provide, for example,
information used by extension elements or extension functions
(see
[14 Extensions]),
information about what to do with the result tree,
information about how to obtain the source tree,
metadata about the stylesheet,
structured documentation for the stylesheet.
2.3 Literal Result Element
as
Stylesheet
A simplified syntax is allowed for stylesheets that consist of only a
single template for the root node. The stylesheet may consist of just a
literal result element (see [7.1.1
Literal Result Elements]). Such a stylesheet is equivalent to a
stylesheet with an xsl:stylesheet element containing a
template
rule containing the literal result element; the template rule has a
match
pattern of /. For example
<html xsl:version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/TR/xhtml1/strict">
<head>
<title>Expense Report Summary</title>
</head>
<body>
<p>Total Amount: <xsl:value-of select="expense-report/total"/></p>
</body>
</html>
has the same meaning as
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/TR/xhtml1/strict">
<xsl:template match="/">
<html>
<head>
<title>Expense Report Summary</title>
</head>
<body>
<p>Total Amount: <xsl:value-of select="expense-report/total"/></p>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
A literal result element that is the document element of a stylesheet
must
have an xsl:version attribute, which indicates the version
of
XSLT that the stylesheet requires. For this version of XSLT, the value
should be 1.0; the value must be a Number. Other literal
result
elements may also have an xsl:version attribute. When the
xsl:version attribute is not equal to 1.0,
forwards-compatible processing mode is enabled (see [2.5
Forwards-Compatible Processing]).
The allowed content of a literal result element when used as a
stylesheet
is no different from when it occurs within a stylesheet. Thus, a literal
result element used as a stylesheet cannot contain top-level elements.
In some situations, the only way that a system can recognize that an
XML
document needs to be processed by an XSLT processor as an XSLT
stylesheet is
by examining the XML document itself. Using the simplified syntax makes
this
harder.
NOTE:For example, another XML language (AXL) might also use an
axl:version on the document element to indicate that an
XML
document was an AXL document that required processing by an AXL
processor;
if a document had both an axl:version attribute and an
xsl:version attribute, it would be unclear whether the
document should be processed by an XSLT processor or an AXL
processor.
Therefore, the simplified syntax should not be used for XSLT
stylesheets
that may be used in such a situation. This situation can, for example,
arise
when an XSLT stylesheet is transmitted as a message with a MIME media
type of
text/xml or application/xml to a recipient
that
will use the MIME media type to determine how the message is processed.
2.4 Qualified Names
The name of an internal XSLT object, specifically a named template
(see [6 Named Templates]), a mode
(see [5.7 Modes]), an attribute set (see [7.1.4 Named Attribute Sets]), a key
(see
[12.2 Keys]), a decimal-format (see [12.3 Number Formatting]), a variable
or a
parameter (see [11 Variables and Parameters])
is specified as a QName.
If it has a
prefix, then the prefix is expanded into a URI reference using the
namespace
declarations in effect on the attribute in which the name occurs. The expanded-name
consisting of the local part of the name and the possibly null URI
reference
is used as the name of the object. The default namespace is not
used
for unprefixed names.
2.5 Forwards-Compatible Processing
An element enables forwards-compatible mode for itself, its
attributes,
its descendants and their attributes if either it is an
xsl:stylesheet element whose version attribute
is
not equal to 1.0, or it is a literal result element that
has an
xsl:version attribute whose value is not equal to
1.0, or it is a literal result element that does not have
an
xsl:version attribute and that is the document element of a
stylesheet using the simplified syntax (see [2.3 Literal Result Element as
Stylesheet]). A literal result element that has an
xsl:version attribute whose value is equal to 1.0
disables forwards-compatible mode for itself, its attributes, its
descendants
and their attributes.
If an element is processed in forwards-compatible mode, then:
if it is a top-level element and
XSLT
1.0 does not allow such elements as top-level elements, then the
element
must be ignored along with its content;
if it is an element in a template and XSLT 1.0 does not allow
such
elements to occur in templates, then if the element is not
instantiated,
an error must not be signaled, and if the element is instantiated,
the
XSLT must perform fallback for the element as specified in [15 Fallback];
if the element has an attribute that XSLT 1.0 does not allow
the
element to have or if the element has an optional attribute with a
value
that the XSLT 1.0 does not allow the attribute to have, then the
attribute must be ignored.
Thus, any XSLT 1.0 processor must be able to process the following
stylesheet without error, although the stylesheet includes elements from
the
XSLT namespace that are not defined in this specification:
<xsl:stylesheet version="1.1"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<xsl:choose>
<xsl:when test="system-property('xsl:version') >= 1.1">
<xsl:exciting-new-1.1-feature/>
</xsl:when>
<xsl:otherwise>
<html>
<head>
<title>XSLT 1.1 required</title>
</head>
<body>
<p>Sorry, this stylesheet requires XSLT 1.1.</p>
</body>
</html>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
NOTE:If a stylesheet depends crucially on a top-level element
introduced by a version of XSL after 1.0, then the stylesheet can use
an
xsl:message element with terminate="yes"
(see [13 Messages]) to ensure that XSLT
processors
implementing earlier versions of XSL will not silently ignore the
top-level
element. For example,
<xsl:stylesheet version="1.5"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:important-new-1.1-declaration/>
<xsl:template match="/">
<xsl:choose>
<xsl:when test="system-property('xsl:version') < 1.1">
<xsl:message terminate="yes">
<xsl:text>Sorry, this stylesheet requires XSLT 1.1.</xsl:text>
</xsl:message>
</xsl:when>
<xsl:otherwise>
...
</xsl:otherwise>
</xsl:choose>
</xsl:template>
...
</xsl:stylesheet>
If an expression occurs in an attribute
that
is processed in forwards-compatible mode, then an XSLT processor must
recover
from errors in the expression as follows:
if the expression does not match the syntax allowed by the
XPath
grammar, then an error must not be signaled unless the expression is
actually evaluated;
if the expression calls a function with an unprefixed name that
is
not part of the XSLT library, then an error must not be signaled
unless
the function is actually called;
if the expression calls a function with a number of arguments
that
XSLT does not allow or with arguments of types that XSLT does not
allow,
then an error must not be signaled unless the function is actually
called.
2.6 Combining
Stylesheets
XSLT provides two mechanisms to combine stylesheets:
- an inclusion mechanism that allows stylesheets to be combined
without
changing the semantics of the stylesheets being combined, and
- an import mechanism that allows stylesheets to override each
other.
2.6.1 Stylesheet Inclusion
<!--
Category: top-level-element -->
<xsl:include
href = uri-reference />
An XSLT stylesheet may include another XSLT stylesheet using an
xsl:include element. The xsl:include element
has an
href attribute whose value is a URI reference identifying
the
stylesheet to be included. A relative URI is resolved relative to the
base
URI of the xsl:include element (see [3.2
Base
URI]).
The xsl:include element is only allowed as a top-level element.
The inclusion works at the XML tree level. The resource located by
the
href attribute value is parsed as an XML document, and the
children of the xsl:stylesheet element in this document
replace
the xsl:include element in the including document. The
fact
that template rules or definitions are included does not affect the way
they
are processed.
The included stylesheet may use the simplified syntax described in [2.3 Literal Result Element as
Stylesheet]. The included stylesheet is treated the same as the
equivalent xsl:stylesheet element.
It is an error if a stylesheet directly or indirectly includes
itself.
NOTE:Including a stylesheet multiple times can cause errors
because
of duplicate definitions. Such multiple inclusions are less obvious
when
they are indirect. For example, if stylesheet B includes
stylesheet A, stylesheet C includes stylesheet
A, and stylesheet D includes both stylesheet
B and stylesheet C, then A will be
included indirectly by D twice. If all of B,
C and D are used as independent stylesheets,
then the
error can be avoided by separating everything in B other
than
the inclusion of A into a separate stylesheet B'
and
changing B to contain just inclusions of B' and
A, similarly for C, and then changing D
to
include A, B', C'.
2.6.2 Stylesheet Import
<xsl:import
href = uri-reference />
An XSLT stylesheet may import another XSLT stylesheet using an
xsl:import element. Importing a stylesheet is the same as
including it (see [2.6.1 Stylesheet Inclusion])
except that definitions and template rules in the importing stylesheet
take
precedence over template rules and definitions in the imported
stylesheet;
this is described in more detail below. The xsl:import
element
has an href attribute whose value is a URI reference
identifying
the stylesheet to be imported. A relative URI is resolved relative to
the
base URI of the xsl:import element (see [3.2
Base URI]).
The xsl:import element is only allowed as a top-level element. The xsl:import
element children must precede all other element children of an
xsl:stylesheet element, including any xsl:include
element children. When xsl:include is used to include a
stylesheet, any xsl:import elements in the included
document are
moved up in the including document to after any existing
xsl:import elements in the including document.
For example,
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:import href="article.xsl"/>
<xsl:import href="bigfont.xsl"/>
<xsl:attribute-set name="note-style">
<xsl:attribute name="font-style">italic</xsl:attribute>
</xsl:attribute-set>
</xsl:stylesheet>
The xsl:stylesheet elements
encountered during processing of a stylesheet that contains
xsl:import elements are treated as forming an import
tree. In the import tree, each xsl:stylesheet element
has
one import child for each xsl:import element that it
contains.
Any xsl:include elements are resolved before constructing
the
import tree. An
xsl:stylesheet element in the import tree is defined to
have
lower import precedence than another xsl:stylesheet
element in the import tree if it would be visited before that
xsl:stylesheet element in a post-order traversal of the
import
tree (i.e. a traversal of the import tree in which an
xsl:stylesheet element is visited after its import
children).
Each definition and template rule has import precedence determined by
the
xsl:stylesheet element that contains it.
For example, suppose
stylesheet A imports stylesheets B and
C in that order;
stylesheet B imports stylesheet D;
stylesheet C imports stylesheet E.
Then the order of import precedence (lowest first) is D,
B, E, C, A.
NOTE:Since xsl:import elements are required to
occur
before any definitions or template rules, an implementation that
processes
imported stylesheets at the point at which it encounters the
xsl:import element will encounter definitions and
template
rules in increasing order of import precedence.
In general, a definition or template rule with higher import
precedence
takes precedence over a definition or template rule with lower import
precedence. This is defined in detail for each kind of definition and
for
template rules.
It is an error if a stylesheet directly or indirectly imports itself.
Apart from this, the case where a stylesheet with a particular URI is
imported in multiple places is not treated specially. The import tree will have a separate
xsl:stylesheet for each place that it is imported.
NOTE:If xsl:apply-imports is used (see [5.6 Overriding Template Rules]), the
behavior may be different from the behavior if the stylesheet had been
imported only at the place with the highest import precedence.
2.7 Embedding
Stylesheets
Normally an XSLT stylesheet is a complete XML document with the
xsl:stylesheet element as the document element. However, an
XSLT
stylesheet may also be embedded in another resource. Two forms of
embedding
are possible:
- the XSLT stylesheet may be textually embedded in a non-XML
resource,
or
- the
xsl:stylesheet element may occur in an XML
document
other than as the document element.
To facilitate the second form of embedding, the
xsl:stylesheet element is allowed to have an ID attribute
that
specifies a unique identifier.
NOTE:In order for such an attribute to be used with the XPath id function, it
must
actually be declared in the DTD as being an ID.
The following example shows how the xml-stylesheet
processing
instruction [XML Stylesheet] can be used to
allow a
document to contain its own stylesheet. The URI reference uses a
relative
URI with a fragment identifier to locate the xsl:stylesheet
element:
<?xml-stylesheet type="text/xml" href="#style1"?>
<!DOCTYPE doc SYSTEM "doc.dtd">
<doc>
<head>
<xsl:stylesheet id="style1"
version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:fo="http://www.w3.org/1999/XSL/Format">
<xsl:import href="doc.xsl"/>
<xsl:template match="id('foo')">
<fo:block font-weight="bold"><xsl:apply-templates/></fo:block>
</xsl:template>
<xsl:template match="xsl:stylesheet">
<!-- ignore -->
</xsl:template>
</xsl:stylesheet>
</head>
<body>
<para id="foo">
...
</para>
</body>
</doc>
NOTE:A stylesheet that is embedded in the document to which it
is to
be applied or that may be included or imported into an stylesheet that
is
so embedded typically needs to contain a template rule that specifies
that
xsl:stylesheet elements are to be ignored.
3 Data Model
The data model used by XSLT is the same as that used by XPath with the
additions
described in this section. XSLT operates on source, result and
stylesheet
documents using the same data model. Any two XML documents that have
the
same tree will be treated the same by XSLT.
Processing instructions and comments in the stylesheet are ignored:
the
stylesheet is treated as if neither processing instruction nodes nor
comment
nodes were included in the tree that represents the stylesheet.
3.1 Root Node Children
The normal restrictions on the children of the root node are relaxed
for
the result tree. The result tree may have any sequence of nodes as
children
that would be possible for an element node. In particular, it may have
text
node children, and any number of element node children. When written out
using the XML output method (see [16 Output]),
it
is possible that a result tree will not be a well-formed XML document;
however, it will always be a well-formed external general parsed entity.
When the source tree is created by parsing a well-formed XML
document, the
root node of the source tree will automatically satisfy the normal
restrictions of having no text node children and exactly one element
child.
When the source tree is created in some other way, for example by using
the
DOM, the usual restrictions are relaxed for the source tree as for the
result
tree.
3.2 Base URI
Every node also has an associated URI called its base URI, which is
used
for resolving attribute values that represent relative URIs into
absolute
URIs. If an element or processing instruction occurs in an external
entity,
the base URI of that element or processing instruction is the URI of the
external entity; otherwise, the base URI is the base URI of the
document.
The base URI of the document node is the URI of the document entity.
The
base URI for a text node, a comment node, an attribute node or a
namespace
node is the base URI of the parent of the node.
3.3 Unparsed Entities
The root node has a mapping that gives the URI for each unparsed
entity
declared in the document's DTD. The URI is generated from the system
identifier and public identifier specified in the entity declaration.
The
XSLT processor may use the public identifier to generate a URI for the
entity
instead of the URI specified in the system identifier. If the XSLT
processor
does not use the public identifier to generate the URI, it must use the
system identifier; if the system identifier is a relative URI, it must
be
resolved into an absolute URI using the URI of the resource containing
the
entity declaration as the base URI [RFC2396].
3.4 Whitespace Stripping
After the tree for a source document or stylesheet document has been
constructed, but before it is otherwise processed by XSLT, some text
nodes
are stripped. A text node is never stripped unless it contains only
whitespace characters. Stripping the text node removes the text node
from
the tree. The stripping process takes as input a set of element names
for
which whitespace must be preserved. The stripping process is applied to
both
stylesheets and source documents, but the set of whitespace-preserving
element names is determined differently for stylesheets and for source
documents.
A text node is preserved if any of the following apply:
The element name of the parent of the text node is in the set
of
whitespace-preserving element names.
The text node contains at least one non-whitespace character.
As in
XML, a whitespace character is #x20, #x9, #xD or #xA.
An ancestor element of the text node has an xml:space
attribute with a value of preserve, and no closer
ancestor
element has xml:space with a value of
default.
Otherwise, the text node is stripped.
The xml:space attributes are not stripped from the tree.
NOTE:This implies that if an xml:space attribute
is
specified on a literal result element, it will be included in the
result.
For stylesheets, the set of whitespace-preserving element names
consists
of just xsl:text.
<!--
Category:
top-level-element -->
<xsl:strip-space
elements = tokens />
<!--
Category:
top-level-element -->
<xsl:preserve-space
elements = tokens />
For source documents, the set of whitespace-preserving element names
is
specified by xsl:strip-space and xsl:preserve-space
top-level elements. These elements each
have an
elements attribute whose value is a whitespace-separated
list of
NameTests.
Initially,
the set of whitespace-preserving element names contains all element
names. If
an element name matches a NameTest in an
xsl:strip-space element, then it is removed from the set of
whitespace-preserving element names. If an element name matches a NameTest in an
xsl:preserve-space element, then it is added to the set of
whitespace-preserving element names. An element matches a NameTest if and only
if the
NameTest would be
true
for the element as an XPath
node
test. Conflicts between matches to xsl:strip-space
and
xsl:preserve-space elements are resolved the same way as
conflicts between template rules (see [5.5
Conflict
Resolution for Template Rules]). Thus, the applicable match for
a
particular element name is determined as follows:
It is an error if this leaves more than one match. An XSLT processor
may
signal the error; if it does not signal the error, it must recover by
choosing, from amongst the matches that are left, the one that occurs
last in
the stylesheet.
4 Expressions
XSLT uses the expression language defined by XPath [XPath].
Expressions are used in XSLT for a variety of
purposes including:
- selecting nodes for processing;
- specifying conditions for different ways of processing a node;
- generating text to be inserted in the result tree.
An expression must match the XPath
production Expr.
Expressions occur as the value of certain attributes on XSLT-defined
elements and within curly braces in attribute value templates.
In XSLT, an outermost expression (i.e. an expression that is not part
of
another expression) gets its context as follows:
the context node comes from the current
node
the context position comes from the position of the current node in the current node list; the first position
is
1
the context size comes from the size of the current node list
the variable bindings are the bindings in scope on the element
which
has the attribute in which the expression occurs (see [11 Variables and Parameters])
the set of namespace declarations are those in scope on the
element
which has the attribute in which the expression occurs; this
includes the
implicit declaration of the prefix xml required by the
the
XML Namespaces Recommendation [XML Names];
the
default namespace (as declared by xmlns) is not part of
this
set
the function library consists of the core function library
together
with the additional functions defined in [12
Additional Functions] and extension functions as described
in [14 Extensions]; it is an error for
an
expression to include a call to any other function
5 Template Rules
5.1 Processing Model
A list of source nodes is processed to create a result tree fragment.
The
result tree is constructed by processing a list containing just the root
node. A list of source nodes is processed by appending the result tree
structure created by processing each of the members of the list in
order. A
node is processed by finding all the template rules with patterns that
match
the node, and choosing the best amongst them; the chosen rule's template
is
then instantiated with the node as the current
node and with the list of source nodes as the current node list. A template
typically
contains instructions that select an additional list of source nodes for
processing. The process of matching, instantiation and selection is
continued recursively until no new source nodes are selected for
processing.
Implementations are free to process the source document in any way
that
produces the same result as if it were processed using this processing
model.
5.2 Patterns
Template rules identify the nodes to which
they
apply by using a pattern. As well as being used in template
rules,
patterns are used for numbering (see [7.7
Numbering]) and for declaring keys (see [12.2
Keys]). A pattern specifies a set of conditions on a node. A
node
that satisfies the conditions matches the pattern; a node that does not
satisfy the conditions does not match the pattern. The syntax for
patterns
is a subset of the syntax for expressions. In particular, location paths
that
meet certain restrictions can be used as patterns. An expression that
is
also a pattern always evaluates to an object of type node-set. A node
matches a pattern if the node is a member of the result of evaluating
the
pattern as an expression with respect to some possible context; the
possible
contexts are those whose context node is the node being matched or one
of its
ancestors.
Here are some examples of patterns:
para matches any para element
* matches any element
chapter|appendix matches any chapter
element and any appendix element
olist/item matches any item element
with
an olist parent
appendix//para matches any para
element
with an appendix ancestor element
/ matches the root node
text() matches any text node
processing-instruction() matches any processing
instruction
node() matches any node other than an attribute
node
and the root node
id("W11") matches the element with unique ID
W11
para[1] matches any para element that
is
the first para child element of its parent
*[position()=1 and self::para] matches any
para element that is the first child element of its
parent
para[last()=1] matches any para
element
that is the only para child element of its parent
items/item[position()>1] matches any
item element that has a items parent and
that
is not the first item child of its parent
item[position() mod 2 = 1] would be true for any
item element that is an odd-numbered item
child
of its parent.
div[@class="appendix"]//p matches any p
element with a div ancestor element that has a
class attribute with value appendix
@class matches any class attribute
(not any element that has a class attribute)
@* matches any attribute
A pattern must match the grammar for Pattern.
A
Pattern is a set of location path patterns
separated by |. A location path pattern is a location path
whose steps all use only the child or attribute
axes. Although patterns must not use the descendant-or-self
axis, patterns may use the // operator as well as the
/ operator. Location path patterns can also start with an id or key function call with a literal argument.
Predicates in a pattern can use arbitrary expressions just like
predicates in
a location path.
Patterns
A pattern is defined to match a node if and only if there is possible
context such that when the pattern is evaluated as an expression with
that
context, the node is a member of the resulting node-set. When a node is
being matched, the possible contexts have a context node that is the
node
being matched or any ancestor of that node, and a context node list
containing just the context node.
For example, p matches any p element,
because
for any p if the expression p is evaluated
with the
parent of the p element as context the resulting node-set
will
contain that p element as one of its members.
NOTE:This matches even a p element that is the
document
element, since the document root is the parent of the document
element.
Although the semantics of patterns are specified indirectly in terms
of
expression evaluation, it is easy to understand the meaning of a pattern
directly without thinking in terms of expression evaluation. In a
pattern,
| indicates alternatives; a pattern with one or more
| separated alternatives matches if any one of the
alternative
matches. A pattern that consists of a sequence of StepPatterns separated by / or
// is matched from right to left. The pattern only matches
if
the rightmost StepPattern matches and a
suitable element matches the rest of the pattern; if the separator is
/ then only the parent is a suitable element; if the
separator
is //, then any ancestor is a suitable element. A StepPattern that uses the child axis matches
if
the NodeTest is
true for
the node and the node is not an attribute node. A StepPattern that uses the attribute axis
matches
if the NodeTest is
true
for the node and the node is an attribute node. When [] is
present, then the first PredicateExpr in a
StepPattern is evaluated with the node
being
matched as the context node and the siblings of the context node that
match
the NodeTest as the
context node list, unless the node being matched is an attribute node,
in
which case the context node list is all the attributes that have the
same
parent as the attribute being matched and that match the NameTest.
For example
appendix//ulist/item[position()=1]
matches a node if and only if all of the following are true:
the NodeTest
item is true for the node and the node is not an
attribute;
in other words the node is an item element
evaluating the PredicateExpr
position()=1 with the node as context node and the
siblings
of the node that are item elements as the context node
list
yields true
the node has a parent that matches appendix//ulist;
this will be true if the parent is a ulist element that
has
an appendix ancestor element.
5.3 Defining Template
Rules
<!--
Category: top-level-element -->
<xsl:template
match = pattern
name = qname
priority = number
mode = qname>
<!-- Content: (xsl:param*,
template) -->
</xsl:template>
A template rule is specified with the xsl:template
element.
The match attribute is a Pattern
that
identifies the source node or nodes to which the rule applies. The
match attribute is required unless the xsl:template
element has a name attribute (see [6 Named Templates]). It is an error
for
the value of the match attribute to contain a VariableReference.
The content of the xsl:template element is the template
that is
instantiated when the template rule is applied.
For example, an XML document might contain:
This is an <emph>important</emph> point.
The following template rule matches emph elements and
produces a fo:inline-sequence formatting object with a
font-weight property of bold.
<xsl:template match="emph">
<fo:inline-sequence font-weight="bold">
<xsl:apply-templates/>
</fo:inline-sequence>
</xsl:template>
NOTE:Examples in this document use the fo: prefix
for
the namespace http://www.w3.org/1999/XSL/Format, which is
the
namespace of the formatting objects defined in [XSL].
As described next, the xsl:apply-templates element
recursively processes the children of the source element.
5.4 Applying Template
Rules
<!--
Category:
instruction -->
<xsl:apply-templates
select = node-set-expression
mode = qname>
<!-- Content: (xsl:sort | xsl:with-param)* -->
</xsl:apply-templates>
This example creates a block for a chapter element and
then
processes its immediate children.
<xsl:template match="chapter">
<fo:block>
<xsl:apply-templates/>
</fo:block>
</xsl:template>
In the absence of a select attribute, the
xsl:apply-templates instruction processes all of the
children of
the current node, including text nodes. However, text nodes that have
been
stripped as specified in [3.4 Whitespace
Stripping] will not be processed. If stripping of whitespace
nodes
has not been enabled for an element, then all whitespace in the content
of
the element will be processed as text, and thus whitespace between child
elements will count in determining the position of a child element as
returned by the position
function.
A select attribute can be used to process nodes selected
by
an expression instead of processing all children. The value of the
select attribute is an expression.
The expression must evaluate to a node-set. The selected set of nodes
is
processed in document order, unless a sorting specification is present
(see
[10 Sorting]). The following example
processes
all of the author children of the author-group:
<xsl:template match="author-group">
<fo:inline-sequence>
<xsl:apply-templates select="author"/>
</fo:inline-sequence>
</xsl:template>
The following example processes all of the given-names
of the
authors that are children of author-group:
<xsl:template match="author-group">
<fo:inline-sequence>
<xsl:apply-templates select="author/given-name"/>
</fo:inline-sequence>
</xsl:template>
This example processes all of the heading descendant
elements
of the book element.
<xsl:template match="book">
<fo:block>
<xsl:apply-templates select=".//heading"/>
</fo:block>
</xsl:template>
It is also possible to process elements that are not descendants of
the
current node. This example assumes that a department
element
has group children and employee descendants.
It
finds an employee's department and then processes the group
children of the department.
<xsl:template match="employee">
<fo:block>
Employee <xsl:apply-templates select="name"/> belongs to group
<xsl:apply-templates select="ancestor::department/group"/>
</fo:block>
</xsl:template>
Multiple xsl:apply-templates elements can be used within
a
single template to do simple reordering. The following example creates
two
HTML tables. The first table is filled with domestic sales while the
second
table is filled with foreign sales.
<xsl:template match="product">
<table>
<xsl:apply-templates select="sales/domestic"/>
</table>
<table>
<xsl:apply-templates select="sales/foreign"/>
</table>
</xsl:template>
NOTE: It is possible for there to be two matching descendants
where
one is a descendant of the other. This case is not treated specially:
both
descendants will be processed as usual. For example, given a source
document
<doc><div><div></div></div></doc>
the rule
<xsl:template match="doc">
<xsl:apply-templates select=".//div"/>
</xsl:template>
will process both the outer div and inner div
elements.
NOTE:Typically, xsl:apply-templates is used to
process
only nodes that are descendants of the current node. Such use of
xsl:apply-templates cannot result in non-terminating
processing loops. However, when xsl:apply-templates is
used
to process elements that are not descendants of the current node, the
possibility arises of non-terminating loops. For example,
<xsl:template match="foo">
<xsl:apply-templates select="."/>
</xsl:template>
Implementations may be able to detect such loops in some cases, but
the
possibility exists that a stylesheet may enter a non-terminating loop
that
an implementation is unable to detect. This may present a denial of
service
security risk.
5.5 Conflict Resolution for Template Rules
It is possible for a source node to match more than one template
rule. The
template rule to be used is determined as follows:
First, all matching template rules that have lower import precedence than the matching
template rule or rules with the highest import precedence are
eliminated
from consideration.
Next, all matching template rules that have lower priority than
the
matching template rule or rules with the highest priority are
eliminated
from consideration. The priority of a template rule is specified by
the
priority attribute on the template rule. The value of
this
must be a real number (positive or negative), matching the
production Number
with an optional
leading minus sign (-). The
default priority is computed as
follows:
Thus, the most common kind of pattern (a pattern that tests for a
node
with a particular type and a particular expanded-name) has priority
0.
The next less specific kind of pattern (a pattern that tests for a
node
with a particular type and an expanded-name with a particular
namespace
URI) has priority -0.25. Patterns less specific than this (patterns
that
just tests for nodes with particular types) have priority -0.5.
Patterns
more specific than the most common kind of pattern have priority
0.5.
It is an error if this leaves more than one matching template rule.
An
XSLT processor may signal the error; if it does not signal the error, it
must
recover by choosing, from amongst the matching template rules that are
left,
the one that occurs last in the stylesheet.
5.6 Overriding Template Rules
<!--
Category:
instruction -->
<xsl:apply-imports />
A template rule that is being used to override a template rule in an
imported stylesheet (see [5.5 Conflict Resolution
for
Template Rules]) can use the xsl:apply-imports
element
to invoke the overridden template rule.
At any point in the processing
of a
stylesheet, there is a current template rule. Whenever a
template
rule is chosen by matching a pattern, the template rule becomes the
current
template rule for the instantiation of the rule's template. When an
xsl:for-each element is instantiated, the current template
rule
becomes null for the instantiation of the content of the
xsl:for-each element.
xsl:apply-imports processes the current node using only
template rules that were imported into the stylesheet element containing
the
current template rule; the node is processed in the current template
rule's
mode. It is an error if xsl:apply-imports is instantiated
when
the current template rule is null.
For example, suppose the stylesheet doc.xsl contains a
template rule for example elements:
<xsl:template match="example">
<pre><xsl:apply-templates/></pre>
</xsl:template>
Another stylesheet could import doc.xsl and modify the
treatment of example elements as follows:
<xsl:import href="doc.xsl"/>
<xsl:template match="example">
<div style="border: solid red">
<xsl:apply-imports/>
</div>
</xsl:template>
The combined effect would be to transform an example
into an
element of the form:
<div style="border: solid red"><pre>...</pre></div>
5.7 Modes
Modes allow an element to be processed multiple times, each time
producing
a different result.
Both xsl:template and xsl:apply-templates
have
an optional mode attribute. The value of the mode
attribute is a QName,
which is
expanded as described in [2.4 Qualified Names].
If xsl:template does not have a match
attribute, it
must not have a mode attribute. If an
xsl:apply-templates element has a mode
attribute,
then it applies only to those template rules from xsl:template
elements that have a mode attribute with the same value; if
an
xsl:apply-templates element does not have a mode
attribute, then it applies only to those template rules from
xsl:template elements that do not have a mode
attribute.
5.8 Built-in Template Rules
There is a built-in template rule to allow recursive processing to
continue in the absence of a successful pattern match by an explicit
template
rule in the stylesheet. This template rule applies to both element
nodes and
the root node. The following shows the equivalent of the built-in
template
rule:
<xsl:template match="*|/">
<xsl:apply-templates/>
</xsl:template>
There is also a built-in template rule for each mode, which allows
recursive processing to continue in the same mode in the absence of a
successful pattern match by an explicit template rule in the stylesheet.
This template rule applies to both element nodes and the root node. The
following shows the equivalent of the built-in template rule for mode
m.
<xsl:template match="*|/" mode="m">
<xsl:apply-templates mode="m"/>
</xsl:template>
There is also a built-in template rule for text and attribute nodes
that
copies text through:
<xsl:template match="text()|@*">
<xsl:value-of select="."/>
</xsl:template>
The built-in template rule for processing instructions and comments
is to
do nothing.
<xsl:template match="processing-instruction()|comment()"/>
The built-in template rule for namespace nodes is also to do nothing.
There is no pattern that can match a namespace node; so, the built-in
template rule is the only template rule that is applied for namespace
nodes.
The built-in template rules are treated as if they were imported
implicitly before the stylesheet and so have lower import precedence than all other
template
rules. Thus, the author can override a built-in template rule by
including
an explicit template rule.
6 Named Templates
<!--
Category:
instruction -->
<xsl:call-template
name = qname>
<!-- Content: xsl:with-param*
-->
</xsl:call-template>
Templates can be invoked by name. An xsl:template
element
with a name attribute specifies a named template. The value
of
the name attribute is a QName, which is
expanded as described in [2.4 Qualified Names].
If an xsl:template element has a name
attribute, it
may, but need not, also have a match attribute. An
xsl:call-template element invokes a template by name; it
has a
required name attribute that identifies the template to be
invoked. Unlike xsl:apply-templates,
xsl:call-template does not change the current node or the
current node list.
The match, mode and priority
attributes on an xsl:template element do not affect whether
the
template is invoked by an xsl:call-template element.
Similarly,
the name attribute on an xsl:template element
does
not affect whether the template is invoked by an
xsl:apply-templates element.
It is an error if a stylesheet contains more than one template with
the
same name and same import precedence.
7 Creating the Result
Tree
This section describes instructions that directly create nodes in the
result tree.
7.1 Creating
Elements and Attributes
7.1.1 Literal Result Elements
In a template, an element in the stylesheet that does not belong to
the
XSLT namespace and that is not an extension element (see [14.1 Extension Elements]) is
instantiated to create an element node with the same expanded-name.
The
content of the element is a template, which is instantiated to give the
content of the created element node. The created element node will have
the
attribute nodes that were present on the element node in the stylesheet
tree,
other than attributes with names in the XSLT namespace.
The created element node will also have a copy of the namespace nodes
that
were present on the element node in the stylesheet tree with the
exception of
any namespace node whose string-value is the XSLT namespace URI
(http://www.w3.org/1999/XSL/Transform), a namespace URI
declared
as an extension namespace (see [14.1
Extension Elements]), or a namespace URI designated as an
excluded
namespace. A namespace URI is designated as an excluded namespace by
using
an exclude-result-prefixes attribute on an
xsl:stylesheet element or an
xsl:exclude-result-prefixes attribute on a literal result
element. The value of both these attributes is a whitespace-separated
list
of namespace prefixes. The namespace bound to each of the prefixes is
designated as an excluded namespace. It is an error if there is no
namespace
bound to the prefix on the element bearing the
exclude-result-prefixes or
xsl:exclude-result-prefixes attribute. The default
namespace
(as declared by xmlns) may be designated as an excluded
namespace by including #default in the list of namespace
prefixes. The designation of a namespace as an excluded namespace is
effective within the subtree of the stylesheet rooted at the element
bearing
the exclude-result-prefixes or
xsl:exclude-result-prefixes attribute; a subtree rooted at
an
xsl:stylesheet element does not include any stylesheets
imported
or included by children of that xsl:stylesheet element.
NOTE:When a stylesheet uses a namespace declaration only for
the
purposes of addressing the source tree, specifying the prefix in the
exclude-result-prefixes attribute will avoid superfluous
namespace declarations in the result tree.
The value of an attribute of a literal result element is interpreted
as an
attribute value template: it
can
contain expressions contained in curly braces ({}).
A namespace URI in the
stylesheet
tree that is being used to specify a namespace URI in the result tree is
called a literal namespace URI. This applies to:
the namespace URI in the expanded-name of a literal result
element
in the stylesheet
the namespace URI in the expanded-name of an attribute
specified on
a literal result element in the stylesheet
the string-value of a namespace node on a literal result
element in
the stylesheet
<!--
Category:
top-level-element -->
<xsl:namespace-alias
stylesheet-prefix = prefix | "#default"
result-prefix = prefix |
"#default" />
A stylesheet can use the
xsl:namespace-alias element to declare that one namespace
URI is
an alias for another namespace URI. When a literal namespace URI has been
declared
to be an alias for another namespace URI, then the namespace URI in the
result tree will be the namespace URI that the literal namespace URI is
an
alias for, instead of the literal namespace URI itself. The
xsl:namespace-alias element declares that the namespace URI
bound to the prefix specified by the stylesheet-prefix
attribute
is an alias for the namespace URI bound to the prefix specified by the
result-prefix attribute. Thus, the
stylesheet-prefix attribute specifies the namespace URI
that
will appear in the stylesheet, and the result-prefix
attribute
specifies the corresponding namespace URI that will appear in the result
tree. The default namespace (as declared by xmlns) may be
specified by using #default instead of a prefix. If a
namespace
URI is declared to be an alias for multiple different namespace URIs,
then
the declaration with the highest import
precedence is used. It is an error if there is more than one such
declaration. An XSLT processor may signal the error; if it does not
signal
the error, it must recover by choosing, from amongst the declarations
with
the highest import precedence, the one that occurs last in the
stylesheet.
When literal result elements are being used to create element,
attribute,
or namespace nodes that use the XSLT namespace URI, the stylesheet must
use
an alias. For example, the stylesheet
<xsl:stylesheet
version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:fo="http://www.w3.org/1999/XSL/Format"
xmlns:axsl="http://www.w3.org/1999/XSL/TransformAlias">
<xsl:namespace-alias stylesheet-prefix="axsl" result-prefix="xsl"/>
<xsl:template match="/">
<axsl:stylesheet>
<xsl:apply-templates/>
</axsl:stylesheet>
</xsl:template>
<xsl:template match="block">
<axsl:template match="{.}">
<fo:block><axsl:apply-templates/></fo:block>
</axsl:template>
</xsl:template>
</xsl:stylesheet>
will generate an XSLT stylesheet from a document of the form:
<elements>
<block>p</block>
<block>h1</block>
<block>h2</block>
<block>h3</block>
<block>h4</block>
</elements>
NOTE:It may be necessary also to use aliases for namespaces
other
than the XSLT namespace URI. For example, literal result elements
belonging to a namespace dealing with digital signatures might cause
XSLT
stylesheets to be mishandled by general-purpose security software;
using an
alias for the namespace would avoid the possibility of such
mishandling.
7.1.2
Creating
Elements with xsl:element
<!--
Category: instruction -->
<xsl:element
name = { qname }
namespace = { uri-reference }
use-attribute-sets = qnames>
<!-- Content: template -->
</xsl:element>
The xsl:element element allows an element to be created
with
a computed name. The expanded-name of
the
element to be created is specified by a required name
attribute
and an optional namespace attribute. The content of the
xsl:element element is a template for the attributes and
children of the created element.
The name attribute is interpreted as an attribute value template. It is
an
error if the string that results from instantiating the attribute value
template is not a QName.
An XSLT
processor may signal the error; if it does not signal the error, then it
must
recover by making the the result of instantiating the
xsl:element element be the sequence of nodes created by
instantiating the content of the xsl:element element,
excluding
any initial attribute nodes. If the namespace attribute is
not
present then the QName
is expanded into
an expanded-name using the namespace declarations in effect for the
xsl:element element, including any default namespace
declaration.
If the namespace attribute is present, then it also is
interpreted as an attribute value
template. The string that results from instantiating the attribute
value
template should be a URI reference. It is not an error if the string is
not
a syntactically legal URI reference. If the string is empty, then the
expanded-name of the element has a null namespace URI. Otherwise, the
string
is used as the namespace URI of the expanded-name of the element to be
created. The local part of the QName specified
by the
name attribute is used as the local part of the
expanded-name of
the element to be created.
XSLT processors may make use of the prefix of the QName specified
in the
name attribute when selecting the prefix used for
outputting the
created element as XML; however, they are not required to do so.
7.1.3 Creating Attributes with
xsl:attribute
<!--
Category: instruction -->
<xsl:attribute
name = { qname }
namespace = { uri-reference }>
<!-- Content: template -->
</xsl:attribute>
The xsl:attribute element can be used to add attributes
to
result elements whether created by literal result elements in the
stylesheet
or by instructions such as xsl:element. The expanded-name of
the
attribute to be created is specified by a required name
attribute and an optional namespace attribute.
Instantiating an
xsl:attribute element adds an attribute node to the
containing
result element node. The content of the xsl:attribute
element is
a template for the value of the created attribute.
The name attribute is interpreted as an attribute value template. It is
an
error if the string that results from instantiating the attribute value
template is not a QName
or is the string
xmlns. An XSLT processor may signal the error; if it does
not
signal the error, it must recover by not adding the attribute to the
result
tree. If the namespace attribute is not present, then the QName is
expanded into
an expanded-name using the namespace declarations in effect for the
xsl:attribute element, not including any default
namespace declaration.
If the namespace attribute is present, then it also is
interpreted as an attribute value
template. The string that results from instantiating it should be a
URI
reference. It is not an error if the string is not a syntactically
legal URI
reference. If the string is empty, then the expanded-name of the
attribute
has a null namespace URI. Otherwise, the string is used as the
namespace URI
of the expanded-name of the attribute to be created. The local part of
the QName
specified by the
name attribute is used as the local part of the
expanded-name of
the attribute to be created.
XSLT processors may make use of the prefix of the QName specified
in the
name attribute when selecting the prefix used for
outputting the
created attribute as XML; however, they are not required to do so and,
if the
prefix is xmlns, they must not do so. Thus, although it is
not
an error to do:
<xsl:attribute name="xmlns:xsl" namespace="whatever">http://www.w3.org/1999/XSL/Transform</xsl:attribute>
it will not result in a namespace declaration being output.
Adding an attribute to an element replaces any existing attribute of
that
element with the same expanded-name.
The following are all errors:
Adding an attribute to an element after children have been
added to
it; implementations may either signal the error or ignore the
attribute.
Adding an attribute to a node that is not an element;
implementations may either signal the error or ignore the attribute.
Creating nodes other than text nodes during the instantiation
of the
content of the xsl:attribute element; implementations
may
either signal the error or ignore the offending nodes.
NOTE:When an xsl:attribute contains a text node
with a
newline, then the XML output must contain a character reference. For
example,
<xsl:attribute name="a">x
y</xsl:attribute>
will result in the output
a="x
y"
(or with any equivalent character reference). The XML output cannot be
a="x
y"
This is because XML 1.0 requires newline characters in attribute
values to
be normalized into spaces but requires character references to newline
characters not to be normalized. The attribute values in the data
model
represent the attribute value after normalization. If a newline
occurring
in an attribute value in the tree were output as a newline character
rather
than as character reference, then the attribute value in the tree
created
by reparsing the XML would contain a space not a newline, which would
mean
that the tree had not been output correctly.
7.1.4 Named Attribute Sets
<!--
Category:
top-level-element -->
<xsl:attribute-set
name = qname
use-attribute-sets = qnames>
<!-- Content: xsl:attribute*
-->
</xsl:attribute-set>
The xsl:attribute-set element defines a named set of
attributes. The name attribute specifies the name of the
attribute set. The value of the name attribute is a QName, which is
expanded as described in [2.4 Qualified Names].
The content of the xsl:attribute-set element consists of
zero or
more xsl:attribute elements that specify the attributes in
the
set.
Attribute sets are used by specifying a use-attribute-sets
attribute on xsl:element, xsl:copy (see [7.5 Copying]) or xsl:attribute-set
elements. The value of the use-attribute-sets attribute is
a
whitespace-separated list of names of attribute sets. Each name is
specified
as a QName,
which
is expanded as described in [2.4 Qualified
Names]. Specifying a use-attribute-sets attribute
is
equivalent to adding xsl:attribute elements for each of the
attributes in each of the named attribute sets to the beginning of the
content of the element with the use-attribute-sets
attribute, in
the same order in which the names of the attribute sets are specified in
the
use-attribute-sets attribute. It is an error if use of
use-attribute-sets attributes on xsl:attribute-set
elements causes an attribute set to directly or indirectly use itself.
Attribute sets can also be used by specifying an
xsl:use-attribute-sets attribute on a literal result
element.
The value of the xsl:use-attribute-sets attribute is a
whitespace-separated list of names of attribute sets. The
xsl:use-attribute-sets attribute has the same effect as the
use-attribute-sets attribute on xsl:element
with
the additional rule that attributes specified on the literal result
element
itself are treated as if they were specified by xsl:attribute
elements before any actual xsl:attribute elements but after
any
xsl:attribute elements implied by the
xsl:use-attribute-sets attribute. Thus, for a literal
result
element, attributes from attribute sets named in an
xsl:use-attribute-sets attribute will be added first, in
the
order listed in the attribute; next, attributes specified on the literal
result element will be added; finally, any attributes specified by
xsl:attribute elements will be added. Since adding an
attribute
to an element replaces any existing attribute of that element with the
same
name, this means that attributes specified in attribute sets can be
overridden by attributes specified on the literal result element itself.
The template within each xsl:attribute element in an
xsl:attribute-set element is instantiated each time the
attribute set is used; it is instantiated using the same current node
and
current node list as is used for instantiating the element bearing the
use-attribute-sets or xsl:use-attribute-sets
attribute. However, it is the position in the stylesheet of the
xsl:attribute element rather than of the element bearing
the
use-attribute-sets or xsl:use-attribute-sets
attribute that determines which variable bindings are visible (see [11 Variables and Parameters]); thus, only
variables and parameters declared by top-level
xsl:variable and xsl:param elements are
visible.
The following example creates a named attribute set
title-style and uses it in a template rule.
<xsl:template match="chapter/heading">
<fo:block quadding="start" xsl:use-attribute-sets="title-style">
<xsl:apply-templates/>
</fo:block>
</xsl:template>
<xsl:attribute-set name="title-style">
<xsl:attribute name="font-size">12pt</xsl:attribute>
<xsl:attribute name="font-weight">bold</xsl:attribute>
</xsl:attribute-set>
Multiple definitions of an attribute set with the same expanded-name
are
merged. An attribute from a definition that has higher import precedence takes precedence over
an
attribute from a definition that has lower import precedence. It is an error if
there
are two attribute sets that have the same expanded-name and equal import
precedence and that both contain the same attribute, unless there is a
definition of the attribute set with higher import precedence that also contains
the
attribute. An XSLT processor may signal the error; if it does not
signal the
error, it must recover by choosing from amongst the definitions that
specify
the attribute that have the highest import precedence the one that was
specified last in the stylesheet. Where the attributes in an attribute
set
were specified is relevant only in merging the attributes into the
attribute
set; it makes no difference when the attribute set is used.
7.2 Creating Text
A template can also contain text nodes. Each text node in a template
remaining after whitespace has been stripped as specified in [3.4 Whitespace Stripping] will create a text
node
with the same string-value in the result tree. Adjacent text nodes in
the
result tree are automatically merged.
Note that text is processed at the tree level. Thus, markup of
< in a template will be represented in the
stylesheet
tree by a text node that includes the character <. This
will
create a text node in the result tree that contains a <
character, which will be represented by the markup <
(or
an equivalent character reference) when the result tree is externalized
as an
XML document (unless output escaping is disabled as described in [16.4 Disabling Output
Escaping]).
<!--
Category:
instruction -->
<xsl:text
disable-output-escaping = "yes" | "no">
<!-- Content: #PCDATA -->
</xsl:text>
Literal data characters may also be wrapped in an xsl:text
element. This wrapping may change what whitespace characters are
stripped
(see [3.4 Whitespace Stripping]) but does
not
affect how the characters are handled by the XSLT processor thereafter.
NOTE:The xml:lang and xml:space
attributes
are not treated specially by XSLT. In particular,
it is the responsibility of the stylesheet author explicitly
to
generate any xml:lang or xml:space
attributes
that are needed in the result;
specifying an xml:lang or xml:space
attribute on an element in the XSLT namespace will not cause any
xml:lang or xml:space attributes to
appear in
the result.
7.3 Creating
Processing Instructions
<!--
Category: instruction
-->
<xsl:processing-instruction
name = { ncname }>
<!-- Content: template -->
</xsl:processing-instruction>
The xsl:processing-instruction element is instantiated
to
create a processing instruction node. The content of the
xsl:processing-instruction element is a template for the
string-value of the processing instruction node. The
xsl:processing-instruction element has a required
name attribute that specifies the name of the processing
instruction node. The value of the name attribute is
interpreted as an attribute value
template.
For example, this
<xsl:processing-instruction name="xml-stylesheet">href="book.css" type="text/css"</xsl:processing-instruction>
would create the processing instruction
<?xml-stylesheet href="book.css" type="text/css"?>
It is an error if the string that results from instantiating the
name attribute is not both an NCName and a PITarget. An XSLT
processor may signal the error; if it does not signal the error, it must
recover by not adding the processing instruction to the result tree.
NOTE:This means that xsl:processing-instruction
cannot
be used to output an XML declaration. The xsl:output
element
should be used instead (see [16
Output]).
It is an error if instantiating the content of
xsl:processing-instruction creates nodes other than text
nodes.
An XSLT processor may signal the error; if it does not signal the error,
it
must recover by ignoring the offending nodes together with their
content.
It is an error if the result of instantiating the content of the
xsl:processing-instruction contains the string
?>. An XSLT processor may signal the error; if it does
not
signal the error, it must recover by inserting a space after any
occurrence
of ? that is followed by a >.
7.4 Creating Comments
<!--
Category: instruction -->
<xsl:comment>
<!-- Content: template -->
</xsl:comment>
The xsl:comment element is instantiated to create a
comment
node in the result tree. The content of the xsl:comment
element
is a template for the string-value of the comment node.
For example, this
<xsl:comment>This file is automatically generated. Do not edit!</xsl:comment>
would create the comment
<!--This file is automatically generated. Do not edit!-->
It is an error if instantiating the content of xsl:comment
creates nodes other than text nodes. An XSLT processor may signal the
error;
if it does not signal the error, it must recover by ignoring the
offending
nodes together with their content.
It is an error if the result of instantiating the content of the
xsl:comment contains the string -- or ends
with
-. An XSLT processor may signal the error; if it does not
signal the error, it must recover by inserting a space after any
occurrence
of - that is followed by another - or that
ends the
comment.
7.5 Copying
<!--
Category:
instruction -->
<xsl:copy
use-attribute-sets = qnames>
<!-- Content: template -->
</xsl:copy>
The xsl:copy element provides an easy way of copying the
current node. Instantiating the xsl:copy element creates a
copy
of the current node. The namespace nodes of the current node are
automatically copied as well, but the attributes and children of the
node are
not automatically copied. The content of the xsl:copy
element
is a template for the attributes and children of the created node; the
content is instantiated only for nodes of types that can have attributes
or
children (i.e. root nodes and element nodes).
The xsl:copy element may have a
use-attribute-sets attribute (see [7.1.4
Named Attribute Sets]). This is used
only when copying element nodes.
The root node is treated specially because the root node of the
result
tree is created implicitly. When the current node is the root node,
xsl:copy will not create a root node, but will just use the
content template.
For example, the identity transformation can be written using
xsl:copy as follows:
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
When the current node is an attribute, then if it would be an error
to use
xsl:attribute to create an attribute with the same name as
the
current node, then it is also an error to use xsl:copy (see
[7.1.3 Creating Attributes with
xsl:attribute]).
The following example shows how xml:lang attributes can
be
easily copied through from source to result. If a stylesheet defines the
following named template:
<xsl:template name="apply-templates-copy-lang">
<xsl:for-each select="@xml:lang">
<xsl:copy/>
</xsl:for-each>
<xsl:apply-templates/>
</xsl:template>
then it can simply do
<xsl:call-template name="apply-templates-copy-lang"/>
instead of
<xsl:apply-templates/>
when it wants to copy the xml:lang attribute.
7.6 Computing
Generated
Text
Within a template, the xsl:value-of element can be used
to
compute generated text, for example by extracting text from the source
tree
or by inserting the value of a variable. The xsl:value-of
element does this with an expression that
is
specified as the value of the select attribute.
Expressions can
also be used inside attribute values of literal result elements by
enclosing
the expression in curly braces ({}).
7.6.1 Generating Text with
xsl:value-of
<!--
Category: instruction -->
<xsl:value-of
select = string-expression
disable-output-escaping = "yes" | "no" />
The xsl:value-of element is instantiated to create a
text
node in the result tree. The required select attribute is
an expression; this expression is evaluated
and the
resulting object is converted to a string as if by a call to the string
function.
The string specifies the string-value of the created text node. If the
string is empty, no text node will be created. The created text node
will be
merged with any adjacent text nodes.
The xsl:copy-of element can be used to copy a node-set
over
to the result tree without converting it to a string. See [11.3 Using Values of Variables and Parameters with
xsl:copy-of].
For example, the following creates an HTML paragraph from a
person element with given-name and
family-name attributes. The paragraph will contain the
value of
the given-name attribute of the current node followed by a
space
and the value of the family-name attribute of the current
node.
<xsl:template match="person">
<p>
<xsl:value-of select="@given-name"/>
<xsl:text> </xsl:text>
<xsl:value-of select="@family-name"/>
</p>
</xsl:template>
For another example, the following creates an HTML paragraph from a
person element with given-name and
family-name children elements. The paragraph will contain
the
string-value of the first given-name child element of the
current node followed by a space and the string-value of the first
family-name child element of the current node.
<xsl:template match="person">
<p>
<xsl:value-of select="given-name"/>
<xsl:text> </xsl:text>
<xsl:value-of select="family-name"/>
</p>
</xsl:template>
The following precedes each procedure element with a
paragraph containing the security level of the procedure. It assumes
that
the security level that applies to a procedure is determined by a
security attribute on the procedure element or on an
ancestor
element of the procedure. It also assumes that if more than one such
element
has a security attribute then the security level is
determined
by the element that is closest to the procedure.
<xsl:template match="procedure">
<fo:block>
<xsl:value-of select="ancestor-or-self::*[@security][1]/@security"/>
</fo:block>
<xsl:apply-templates/>
</xsl:template>
7.6.2 Attribute Value
Templates
In an attribute value that
is
interpreted as an attribute value template, such as an attribute
of a
literal result element, an expression can
be
used by surrounding the expression with curly braces ({}).
The
attribute value template is instantiated by replacing the expression
together
with surrounding curly braces by the result of evaluating the expression
and
converting the resulting object to a string as if by a call to the string
function.
Curly braces are not recognized in an attribute value in an XSLT
stylesheet
unless the attribute is specifically stated to be one that is
interpreted as
an attribute value template; in an element syntax summary, the value of
such
attributes is surrounded by curly braces.
NOTE:Not all attributes are interpreted as attribute value
templates. Attributes whose value is an expression or pattern,
attributes
of top-level elements and attributes that
refer
to named XSLT objects are not interpreted as attribute value
templates. In
addition, xmlns attributes are not interpreted as
attribute
value templates; it would not be conformant with the XML Namespaces
Recommendation to do this.
The following example creates an img result element from
a
photograph element in the source; the value of the
src attribute of the img element is computed
from
the value of the image-dir variable and the string-value of
the
href child of the photograph element; the
value of
the width attribute of the img element is
computed
from the value of the width attribute of the size
child of the photograph element:
<xsl:variable name="image-dir">/images</xsl:variable>
<xsl:template match="photograph">
<img src="{$image-dir}/{href}" width="{size/@width}"/>
</xsl:template>
With this source
<photograph>
<href>headquarters.jpg</href>
<size width="300"/>
</photograph>
the result would be
<img src="/images/headquarters.jpg" width="300"/>
When an attribute value template is instantiated, a double left or
right
curly brace outside an expression will be replaced by a single curly
brace.
It is an error if a right curly brace occurs in an attribute value
template
outside an expression without being followed by a second right curly
brace.
A right curly brace inside a Literal in an
expression is
not recognized as terminating the expression.
Curly braces are not recognized recursively inside
expressions.
For example:
<a href="#{id({@ref})/title}">
is not allowed. Instead, use simply:
<a href="#{id(@ref)/title}">
7.7 Numbering
<!--
Category: instruction -->
<xsl:number
level = "single" | "multiple" | "any"
count = pattern
from = pattern
value = number-expression
format = { string }
lang = { nmtoken }
letter-value = { "alphabetic" | "traditional" }
grouping-separator = { char }
grouping-size = { number } />
The xsl:number element is used to insert a formatted
number
into the result tree. The number to be inserted may be specified by an
expression. The value attribute contains an expression. The expression is evaluated and
the
resulting object is converted to a number as if by a call to the number
function.
The number is rounded to an integer and then converted to a string using
the
attributes specified in [7.7.1 Number to String
Conversion Attributes]; in this context, the value of each of
these
attributes is interpreted as an attribute
value template. After
conversion, the resulting string is inserted in the result tree. For
example,
the following example numbers a sorted list:
<xsl:template match="items">
<xsl:for-each select="item">
<xsl:sort select="."/>
<p>
<xsl:number value="position()" format="1. "/>
<xsl:value-of select="."/>
</p>
</xsl:for-each>
</xsl:template>
If no value attribute is specified, then the
xsl:number element inserts a number based on the position
of the
current node in the source tree. The following attributes control how
the
current node is to be numbered:
The level attribute specifies what levels of the
source
tree should be considered; it has the values single,
multiple or any. The default is
single.
The count attribute is a pattern that specifies
what
nodes should be counted at those levels. If count
attribute
is not specified, then it defaults to the pattern that matches any
node
with the same node type as the current node and, if the current node
has
an expanded-name, with the same expanded-name as the current node.
The from attribute is a pattern that specifies
where
counting starts.
In addition, the attributes specified in [7.7.1
Number to String Conversion Attributes] are used for number to
string
conversion, as in the case when the value attribute is
specified.
The xsl:number element first constructs a list of
positive
integers using the level, count and
from attributes:
When level="single", it goes up to the first node
in
the ancestor-or-self axis that matches the count
pattern,
and constructs a list of length one containing one plus the number
of
preceding siblings of that ancestor that match the count
pattern. If there is no such ancestor, it constructs an empty list.
If
the from attribute is specified, then the only
ancestors
that are searched are those that are descendants of the nearest
ancestor
that matches the from pattern. Preceding siblings has
the
same meaning here as with the preceding-sibling axis.
When level="multiple", it constructs a list of all
ancestors of the current node in document order followed by the
element
itself; it then selects from the list those nodes that match the
count pattern; it then maps each node in the list to
one
plus the number of preceding siblings of that node that match the
count pattern. If the from attribute is
specified, then the only ancestors that are searched are those that
are
descendants of the nearest ancestor that matches the from
pattern. Preceding siblings has the same meaning here as with the
preceding-sibling axis.
When level="any", it constructs a list of length
one
containing the number of nodes that match the count
pattern
and belong to the set containing the current node and all nodes at
any
level of the document that are before the current node in document
order,
excluding any namespace and attribute nodes (in other words the
union of
the members of the preceding and
ancestor-or-self axes). If the from
attribute
is specified, then only nodes after the first node before the
current
node that match the from pattern are considered.
The list of numbers is then converted into a string using the
attributes
specified in [7.7.1 Number to String Conversion
Attributes]; in this context, the value of each of these
attributes
is interpreted as an attribute
value
template. After conversion, the resulting string is inserted in the
result tree.
The following would number the items in an ordered list:
<xsl:template match="ol/item">
<fo:block>
<xsl:number/><xsl:text>. </xsl:text><xsl:apply-templates/>
</fo:block>
<xsl:template>
The following two rules would number title elements.
This is
intended for a document that contains a sequence of chapters followed by
a
sequence of appendices, where both chapters and appendices contain
sections,
which in turn contain subsections. Chapters are numbered 1, 2, 3;
appendices
are numbered A, B, C; sections in chapters are numbered 1.1, 1.2, 1.3;
sections in appendices are numbered A.1, A.2, A.3.
<xsl:template match="title">
<fo:block>
<xsl:number level="multiple"
count="chapter|section|subsection"
format="1.1 "/>
<xsl:apply-templates/>
</fo:block>
</xsl:template>
<xsl:template match="appendix//title" priority="1">
<fo:block>
<xsl:number level="multiple"
count="appendix|section|subsection"
format="A.1 "/>
<xsl:apply-templates/>
</fo:block>
</xsl:template>
The following example numbers notes sequentially within a chapter:
<xsl:template match="note">
<fo:block>
<xsl:number level="any" from="chapter" format="(1) "/>
<xsl:apply-templates/>
</fo:block>
</xsl:template>
The following example would number H4 elements in HTML
with a
three-part label:
<xsl:template match="H4">
<fo:block>
<xsl:number level="any" from="H1" count="H2"/>
<xsl:text>.</xsl:text>
<xsl:number level="any" from="H2" count="H3"/>
<xsl:text>.</xsl:text>
<xsl:number level="any" from="H3" count="H4"/>
<xsl:text> </xsl:text>
<xsl:apply-templates/>
</fo:block>
</xsl:template>
7.7.1 Number to String Conversion Attributes
The following attributes are used to control conversion of a list of
numbers into a string. The numbers are integers greater than 0. The
attributes are all optional.
The main attribute is format. The default value for the
format attribute is 1. The format
attribute is split into a sequence of tokens where each token is a
maximal
sequence of alphanumeric characters or a maximal sequence of
non-alphanumeric
characters. Alphanumeric means any character that has a Unicode
category of
Nd, Nl, No, Lu, Ll, Lt, Lm or Lo. The alphanumeric tokens (format
tokens)
specify the format to be used for each number in the list. If the first
token is a non-alphanumeric token, then the constructed string will
start
with that token; if the last token is non-alphanumeric token, then the
constructed string will end with that token. Non-alphanumeric tokens
that
occur between two format tokens are separator tokens that are used to
join
numbers in the list. The nth format token will be used to
format
the nth number in the list. If there are more numbers than
format
tokens, then the last format token will be used to format remaining
numbers.
If there are no format tokens, then a format token of 1 is
used
to format all numbers. The format token specifies the string to be used
to
represent the number 1. Each number after the first will be separated
from
the preceding number by the separator token preceding the format token
used
to format that number, or, if there are no separator tokens, then by
. (a period character).
Format tokens are a superset of the allowed values for the
type attribute for the OL element in HTML 4.0
and
are interpreted as follows:
Any token where the last character has a decimal digit value of
1
(as specified in the Unicode character property database), and the
Unicode value of preceding characters is one less than the Unicode
value
of the last character generates a decimal representation of the
number
where each number is at least as long as the format token. Thus, a
format token 1 generates the sequence 1 2 ... 10
11 12
..., and a format token 01 generates the
sequence
01 02 ... 09 10 11 12
begin_of_the_skype_highlighting 09
10 11 12 end_of_the_skype_highlighting ...
99 100 101.
A format token A generates the sequence A B C
...
Z AA AB AC....
A format token a generates the sequence a b c
...
z aa ab ac....
A format token i generates the sequence i ii
iii
iv v vi vii viii ix x ....
A format token I generates the sequence I II
III
IV V VI VII VIII IX X ....
Any other format token indicates a numbering sequence that
starts
with that token. If an implementation does not support a numbering
sequence that starts with that token, it must use a format token of
1.
When numbering with an alphabetic sequence, the lang
attribute specifies which language's alphabet is to be used; it has the
same
range of values as xml:lang [XML]; if no
lang value is specified, the language should be determined
from
the system environment. Implementers should document for which
languages
they support numbering.
NOTE:Implementers should not make any assumptions about how
numbering works in particular languages and should properly research
the
languages that they wish to support. The numbering conventions of
many
languages are very different from English.
The letter-value attribute disambiguates between
numbering
sequences that use letters. In many languages there are two commonly
used
numbering sequences that use letters. One numbering sequence assigns
numeric
values to letters in alphabetic sequence, and the other assigns numeric
values to each letter in some other manner traditional in that language.
In
English, these would correspond to the numbering sequences specified by
the
format tokens a and i. In some languages, the
first member of each sequence is the same, and so the format token alone
would be ambiguous. A value of alphabetic specifies the
alphabetic sequence; a value of traditional specifies the
other
sequence. If the letter-value attribute is not specified,
then
it is implementation-dependent how any ambiguity is resolved.
NOTE:It is possible for two conforming XSLT processors not to
convert a number to exactly the same string. Some XSLT processors may
not
support some languages. Furthermore, there may be variations possible
in
the way conversions are performed for any particular language that are
not
specifiable by the attributes on xsl:number. Future
versions
of XSLT may provide additional attributes to provide control over
these
variations. Implementations may also use implementation-specific
namespaced attributes on xsl:number for this.
The grouping-separator attribute gives the separator
used as
a grouping (e.g. thousands) separator in decimal numbering sequences,
and the
optional grouping-size specifies the size (normally 3) of
the
grouping. For example, grouping-separator="," and
grouping-size="3" would produce numbers of the form
1,000,000. If only one of the grouping-separator
and grouping-size attributes is specified, then it is
ignored.
Here are some examples of conversion specifications:
format="ア" specifies Katakana numbering
format="イ" specifies Katakana numbering
in
the "iroha" order
format="๑" specifies numbering with
Thai
digits
format="א" letter-value="traditional"
specifies "traditional" Hebrew numbering
format="ა" letter-value="traditional"
specifies Georgian numbering
format="α" letter-value="traditional"
specifies "classical" Greek numbering
format="а" letter-value="traditional"
specifies Old Slavic numbering
8 Repetition
<!--
Category: instruction -->
<xsl:for-each
select = node-set-expression>
<!-- Content: (xsl:sort*,
template) -->
</xsl:for-each>
When the result has a known regular structure, it is useful to be
able to
specify directly the template for selected nodes. The
xsl:for-each instruction contains a template, which is
instantiated for each node selected by the expression
specified by the select
attribute. The select attribute is required. The
expression
must evaluate to a node-set. The template is instantiated with the
selected
node as the current node, and with a list
of
all of the selected nodes as the current
node
list. The nodes are processed in document order, unless a sorting
specification is present (see [10 Sorting]).
For example, given an XML document with this structure
<customers>
<customer>
<name>...</name>
<order>...</order>
<order>...</order>
</customer>
<customer>
<name>...</name>
<order>...</order>
<order>...</order>
</customer>
</customers>
the following would create an HTML document containing a table with a
row
for each customer element
<xsl:template match="/">
<html>
<head>
<title>Customers</title>
</head>
<body>
<table>
<tbody>
<xsl:for-each select="customers/customer">
<tr>
<th>
<xsl:apply-templates select="name"/>
</th>
<xsl:for-each select="order">
<td>
<xsl:apply-templates/>
</td>
</xsl:for-each>
</tr>
</xsl:for-each>
</tbody>
</table>
</body>
</html>
</xsl:template>
9 Conditional
Processing
There are two instructions in XSLT that support conditional
processing in
a template: xsl:if and xsl:choose. The
xsl:if instruction provides simple if-then conditionality;
the
xsl:choose instruction supports selection of one choice
when
there are several possibilities.
9.1
Conditional
Processing with xsl:if
<!--
Category:
instruction -->
<xsl:if
test = boolean-expression>
<!-- Content: template -->
</xsl:if>
The xsl:if element has a test attribute,
which
specifies an expression. The content is a
template. The expression is evaluated and the resulting object is
converted
to a boolean as if by a call to the boolean
function.
If the result is true, then the content template is instantiated;
otherwise,
nothing is created. In the following example, the names in a group of
names
are formatted as a comma separated list:
<xsl:template match="namelist/name">
<xsl:apply-templates/>
<xsl:if test="not(position()=last())">, </xsl:if>
</xsl:template>
The following colors every other table row yellow:
<xsl:template match="item">
<tr>
<xsl:if test="position() mod 2 = 0">
<xsl:attribute name="bgcolor">yellow</xsl:attribute>
</xsl:if>
<xsl:apply-templates/>
</tr>
</xsl:template>
9.2
Conditional Processing with xsl:choose
<!--
Category: instruction -->
<xsl:choose>
<!-- Content: (xsl:when+, xsl:otherwise?) -->
</xsl:choose>
<xsl:when
test = boolean-expression>
<!-- Content: template -->
</xsl:when>
<xsl:otherwise>
<!-- Content: template -->
</xsl:otherwise>
The xsl:choose element selects one among a number of
possible
alternatives. It consists of a sequence of xsl:when
elements
followed by an optional xsl:otherwise element. Each
xsl:when element has a single attribute, test,
which specifies an expression. The content
of
the xsl:when and xsl:otherwise elements is a
template. When an xsl:choose element is processed, each of
the
xsl:when elements is tested in turn, by evaluating the
expression and converting the resulting object to a boolean as if by a
call
to the boolean
function.
The content of the first, and only the first, xsl:when
element
whose test is true is instantiated. If no xsl:when is
true, the
content of the xsl:otherwise element is instantiated. If no
xsl:when element is true, and no xsl:otherwise
element is present, nothing is created.
The following example enumerates items in an ordered list using
arabic
numerals, letters, or roman numerals depending on the depth to which the
ordered lists are nested.
<xsl:template match="orderedlist/listitem">
<fo:list-item indent-start='2pi'>
<fo:list-item-label>
<xsl:variable name="level"
select="count(ancestor::orderedlist) mod 3"/>
<xsl:choose>
<xsl:when test='$level=1'>
<xsl:number format="i"/>
</xsl:when>
<xsl:when test='$level=2'>
<xsl:number format="a"/>
</xsl:when>
<xsl:otherwise>
<xsl:number format="1"/>
</xsl:otherwise>
</xsl:choose>
<xsl:text>. </xsl:text>
</fo:list-item-label>
<fo:list-item-body>
<xsl:apply-templates/>
</fo:list-item-body>
</fo:list-item>
</xsl:template>
10 Sorting
<xsl:sort
select = string-expression
lang = { nmtoken }
data-type = { "text" | "number" | qname-but-not-ncname
}
order = { "ascending" | "descending" }
case-order = { "upper-first" | "lower-first"
} />
Sorting is specified by adding xsl:sort elements as
children
of an xsl:apply-templates or xsl:for-each
element.
The first xsl:sort child specifies the primary sort key,
the
second xsl:sort child specifies the secondary sort key and
so
on. When an xsl:apply-templates or xsl:for-each
element has one or more xsl:sort children, then instead of
processing the selected nodes in document order, it sorts the nodes
according
to the specified sort keys and then processes them in sorted order.
When
used in xsl:for-each, xsl:sort elements must
occur
first. When a template is instantiated by xsl:apply-templates
and xsl:for-each, the current
node
list list consists of the complete list of nodes being processed in
sorted order.
xsl:sort has a select attribute whose value
is
an expression. For each node to be
processed,
the expression is evaluated with that node as the current node and with
the
complete list of nodes being processed in unsorted order as the current
node
list. The resulting object is converted to a string as if by a call to
the
string
function; this string is used as the sort key for that node. The default
value of the select attribute is ., which will
cause the string-value of the current node to be used as the sort key.
This string serves as a sort key for the node. The following
optional
attributes on xsl:sort control how the list of sort keys
are
sorted; the values of all of these attributes are interpreted as attribute value templates.
order specifies whether the strings should be
sorted in
ascending or descending order; ascending specifies
ascending
order; descending specifies descending order; the
default is
ascending
lang specifies the language of the sort keys; it
has
the same range of values as xml:lang [XML];
if no lang value is specified, the
language should be determined from the system environment
data-type specifies the data type of the strings;
the
following values are allowed:
text specifies that the sort keys should be
sorted
lexicographically in the culturally correct manner for the
language
specified by lang
number specifies that the sort keys should be
converted to numbers and then sorted according to the numeric
value;
the sort key is converted to a number as if by a call to the number
function; the lang attribute is ignored
a QName
with a
prefix is expanded into an expanded-name
as described in [2.4 Qualified Names];
the expanded-name identifies the data-type; the behavior in this
case
is not specified by this document
The default value is text.
NOTE:The XSL Working Group plans that future versions of
XSLT
will leverage XML Schemas to define further values for this
attribute.
case-order has the value upper-first
or
lower-first; this applies when
data-type="text", and specifies that upper-case letters
should sort before lower-case letters or vice-versa respectively.
For
example, if lang="en", then A a B b are
sorted
with case-order="upper-first" and a A b B
are
sorted with case-order="lower-first". The default value
is
language dependent.
NOTE:It is possible for two conforming XSLT processors not to
sort
exactly the same. Some XSLT processors may not support some
languages.
Furthermore, there may be variations possible in the sorting of any
particular language that are not specified by the attributes on
xsl:sort, for example, whether Hiragana or Katakana is
sorted
first in Japanese. Future versions of XSLT may provide additional
attributes to provide control over these variations. Implementations
may
also use implementation-specific namespaced attributes on
xsl:sort for this.
NOTE:It is recommended that implementers consult [UNICODE TR10] for information on
internationalized sorting.
The sort must be stable: in the sorted list of nodes, any sub list
that
has sort keys that all compare equal must be in document order.
For example, suppose an employee database has the form
<employees>
<employee>
<name>
<given>James</given>
<family>Clark</family>
</name>
...
</employee>
</employees>
Then a list of employees sorted by name could be generated using:
<xsl:template match="employees">
<ul>
<xsl:apply-templates select="employee">
<xsl:sort select="name/family"/>
<xsl:sort select="name/given"/>
</xsl:apply-templates>
</ul>
</xsl:template>
<xsl:template match="employee">
<li>
<xsl:value-of select="name/given"/>
<xsl:text> </xsl:text>
<xsl:value-of select="name/family"/>
</li>
</xsl:template>
11 Variables and Parameters
<!--
Category: top-level-element -->
<!-- Category: instruction -->
<xsl:variable
name = qname
select = expression>
<!-- Content: template -->
</xsl:variable>
<!--
Category:
top-level-element -->
<xsl:param
name = qname
select = expression>
<!-- Content: template -->
</xsl:param>
A variable is a name that may be bound to a value. The value to
which a
variable is bound (the value of the variable) can be an object of
any
of the types that can be returned by expressions. There are two elements
that
can be used to bind variables: xsl:variable and
xsl:param. The difference is that the value specified on
the
xsl:param variable is only a default value for the binding;
when
the template or stylesheet within which the xsl:param
element
occurs is invoked, parameters may be passed that are used in place of
the
default values.
Both xsl:variable and xsl:param have a
required
name attribute, which specifies the name of the variable.
The
value of the name attribute is a QName, which is
expanded as described in [2.4 Qualified
Names].
For any use of these variable-binding elements, there is a region of
the
stylesheet tree within which the binding is visible; within this region,
any
binding of the variable that was visible on the variable-binding element
itself is hidden. Thus, only the innermost binding of a variable is
visible.
The set of variable bindings in scope for an expression consists of
those
bindings that are visible at the point in the stylesheet where the
expression
occurs.
11.1 Result Tree
Fragments
Variables introduce an additional data-type into the expression
language.
This additional data type is
called
result tree fragment. A variable may be bound to a result tree
fragment instead of one of the four basic XPath data-types (string,
number,
boolean, node-set). A result tree fragment represents a fragment of the
result tree. A result tree fragment is treated equivalently to a
node-set
that contains just a single root node. However, the operations permitted
on a
result tree fragment are a subset of those permitted on a node-set. An
operation is permitted on a result tree fragment only if that operation
would
be permitted on a string (the operation on the string may involve first
converting the string to a number or boolean). In particular, it is not
permitted to use the /, //, and []
operators on result tree fragments. When a permitted operation is
performed
on a result tree fragment, it is performed exactly as it would be on the
equivalent node-set.
When a result tree fragment is copied into the result tree (see [11.3 Using Values of Variables and Parameters with
xsl:copy-of]), then all the nodes that are children
of
the root node in the equivalent node-set are added in sequence to the
result
tree.
Expressions can only return values of type result tree fragment by
referencing variables of type result tree fragment or calling extension
functions that return a result tree fragment or getting a system
property
whose value is a result tree fragment.
11.2 Values of Variables and
Parameters
A variable-binding element can specify the value of the variable in
three
alternative ways.
If the variable-binding element has a select
attribute,
then the value of the attribute must be an expression
and the value of the variable is the
object that results from evaluating the expression. In this case,
the
content must be empty.
If the variable-binding element does not have a select
attribute and has non-empty content (i.e. the variable-binding
element
has one or more child nodes), then the content of the
variable-binding
element specifies the value. The content of the variable-binding
element
is a template, which is instantiated to give the value of the
variable.
The value is a result tree fragment equivalent to a node-set
containing
just a single root node having as children the sequence of nodes
produced
by instantiating the template. The base URI of the nodes in the
result
tree fragment is the base URI of the variable-binding element.
It is an error if a member of the sequence of nodes created by
instantiating the template is an attribute node or a namespace node,
since a root node cannot have an attribute node or a namespace node
as a
child. An XSLT processor may signal the error; if it does not signal
the
error, it must recover by not adding the attribute node or namespace
node.
If the variable-binding element has empty content and does not
have
a select attribute, then the value of the variable is
an
empty string. Thus
<xsl:variable name="x"/>
is equivalent to
<xsl:variable name="x" select="''"/>
NOTE:When a variable is used to select nodes by position, be
careful
not to do:
<xsl:variable name="n">2</xsl:variable>
...
<xsl:value-of select="item[$n]"/>
This will output the value of the first item element, because the
variable
n will be bound to a result tree fragment, not a number.
Instead, do either
<xsl:variable name="n" select="2"/>
...
<xsl:value-of select="item[$n]"/>
or
<xsl:variable name="n">2</xsl:variable>
...
<xsl:value-of select="item[position()=$n]"/>
NOTE:One convenient way to specify the empty node-set as the
default
value of a parameter is:
<xsl:param name="x" select="/.."/>
11.3 Using Values of Variables and Parameters
with
xsl:copy-of
<!--
Category: instruction -->
<xsl:copy-of
select = expression />
The xsl:copy-of element can be used to insert a result
tree
fragment into the result tree, without first converting it to a string
as
xsl:value-of does (see [7.6.1
Generating
Text with xsl:value-of]). The required
select attribute contains an expression.
When the result of evaluating the
expression is a result tree fragment, the complete fragment is copied
into
the result tree. When the result is a node-set, all the nodes in the
set are
copied in document order into the result tree; copying an element node
copies
the attribute nodes, namespace nodes and children of the element node as
well
as the element node itself; a root node is copied by copying its
children.
When the result is neither a node-set nor a result tree fragment, the
result
is converted to a string and then inserted into the result tree, as with
xsl:value-of.
11.4 Top-level Variables and
Parameters
Both xsl:variable and xsl:param are allowed
as
top-level elements. A top-level
variable-binding
element declares a global variable that is visible everywhere. A
top-level
xsl:param element declares a parameter to the stylesheet;
XSLT
does not define the mechanism by which parameters are passed to the
stylesheet. It is an error if a stylesheet contains more than one
binding of
a top-level variable with the same name and same import precedence. At the top-level,
the
expression or template specifying the variable value is evaluated with
the
same context as that used to process the root node of the source
document:
the current node is the root node of the source document and the current
node
list is a list containing just the root node of the source document. If
the
template or expression specifying the value of a global variable x
references a global variable y, then the value for y
must be computed before the value of x. It is an error if it
is
impossible to do this for all global variable definitions; in other
words, it
is an error if the definitions are circular.
This example declares a global variable para-font-size,
which
it references in an attribute value template.
<xsl:variable name="para-font-size">12pt</xsl:variable>
<xsl:template match="para">
<fo:block font-size="{$para-font-size}">
<xsl:apply-templates/>
</fo:block>
</xsl:template>
11.5 Variables and Parameters within
Templates
As well as being allowed at the top-level, both xsl:variable
and xsl:param are also allowed in templates.
xsl:variable is allowed anywhere within a template that an
instruction is allowed. In this case, the binding is visible for all
following siblings and their descendants. Note that the binding is not
visible for the xsl:variable element itself.
xsl:param is allowed as a child at the beginning of an
xsl:template element. In this context, the binding is
visible
for all following siblings and their descendants. Note that the binding
is
not visible for the xsl:param element itself.
A binding shadows another binding if
the
binding occurs at a point where the other binding is visible, and the
bindings have the same name. It is an error if a binding established by
an
xsl:variable or xsl:param element within a
template
shadows another binding established by an
xsl:variable or xsl:param element also within
the
template. It is not an error if a binding established by an
xsl:variable or xsl:param element in a
template shadows another binding established
by an
xsl:variable or xsl:param top-level element. Thus, the following is an
error:
<xsl:template name="foo">
<xsl:param name="x" select="1"/>
<xsl:variable name="x" select="2"/>
</xsl:template>
However, the following is allowed:
<xsl:param name="x" select="1"/>
<xsl:template name="foo">
<xsl:variable name="x" select="2"/>
</xsl:template>
NOTE:The nearest equivalent in Java to an xsl:variable
element in a template is a final local variable declaration with an
initializer. For example,
<xsl:variable name="x" select="'value'"/>
has similar semantics to
final Object x = "value";
XSLT does not provide an equivalent to the Java assignment operator
x = "value";
because this would make it harder to create an implementation that
processes a document other than in a batch-like way, starting at the
beginning and continuing through to the end.
11.6 Passing
Parameters to Templates
<xsl:with-param
name = qname
select = expression>
<!-- Content: template -->
</xsl:with-param>
Parameters are passed to templates using the xsl:with-param
element. The required name attribute specifies the name of
the
parameter (the variable the value of whose binding is to be replaced).
The
value of the name attribute is a QName, which is
expanded as described in [2.4 Qualified Names].
xsl:with-param is allowed within both
xsl:call-template and xsl:apply-templates.
The
value of the parameter is specified in the same way as for
xsl:variable and xsl:param. The current node
and
current node list used for computing the value specified by
xsl:with-param element is the same as that used for the
xsl:apply-templates or xsl:call-template
element
within which it occurs. It is not an error to pass a parameter x
to a template that does not have an xsl:param element for
x; the parameter is simply ignored.
This example defines a named template for a numbered-block
with an argument to control the format of the number.
<xsl:template name="numbered-block">
<xsl:param name="format">1. </xsl:param>
<fo:block>
<xsl:number format="{$format}"/>
<xsl:apply-templates/>
</fo:block>
</xsl:template>
<xsl:template match="ol//ol/li">
<xsl:call-template name="numbered-block">
<xsl:with-param name="format">a. </xsl:with-param>
</xsl:call-template>
</xsl:template>
12 Additional Functions
This section describes XSLT-specific additions to the core XPath
function
library. Some of these additional functions also make use of
information
specified by top-level elements in the
stylesheet; this section also describes these elements.
12.1 Multiple Source Documents
Function: node-set
document(object, node-set?)
The document function allows
access to XML documents other than the main source document.
When the document function
has
exactly one argument and the argument is a node-set, then the result is
the
union, for each node in the argument node-set, of the result of calling
the
document function with the first
argument being the string-value
of the
node, and the second argument being a node-set with the node as its only
member. When the document
function
has two arguments and the first argument is a node-set, then the result
is
the union, for each node in the argument node-set, of the result of
calling
the document function with the
first
argument being the string-value
of the
node, and with the second argument being the second argument passed to
the
document function.
When the first argument to the document
function is not a node-set, the
first argument is converted to a string as if by a call to the string
function.
This string is treated as a URI reference; the resource identified by
the URI
is retrieved. The data resulting from the retrieval action is parsed as
an
XML document and a tree is constructed in accordance with the data model
(see
[3 Data Model]). If there is an error
retrieving the resource, then the XSLT processor may signal an error; if
it
does not signal an error, it must recover by returning an empty
node-set.
One possible kind of retrieval error is that the XSLT processor does not
support the URI scheme used by the URI. An XSLT processor is not
required to
support any particular URI schemes. The documentation for an XSLT
processor
should specify which URI schemes the XSLT processor supports.
If the URI reference does not contain a fragment identifier, then a
node-set containing just the root node of the document is returned. If
the
URI reference does contain a fragment identifier, the function returns a
node-set containing the nodes in the tree identified by the fragment
identifier of the URI reference. The semantics of the fragment
identifier is
dependent on the media type of the result of retrieving the URI. If
there is
an error in processing the fragment identifier, the XSLT processor may
signal
the error; if it does not signal the error, it must recover by returning
an
empty node-set. Possible errors include:
The fragment identifier identifies something that cannot be
represented by an XSLT node-set (such as a range of characters
within a
text node).
The XSLT processor does not support fragment identifiers for
the
media-type of the retrieval result. An XSLT processor is not
required to
support any particular media types. The documentation for an XSLT
processor should specify for which media types the XSLT processor
supports fragment identifiers.
The data resulting from the retrieval action is parsed as an XML
document
regardless of the media type of the retrieval result; if the top-level
media
type is text, then it is parsed in the same way as if the
media
type were text/xml; otherwise, it is parsed in the same way
as
if the media type were application/xml.
NOTE:Since there is no top-level xml media type,
data
with a media type other than text/xml or
application/xml may in fact be XML.
The URI reference may be relative. The base URI (see [3.2 Base URI]) of the node in the second
argument node-set that is first in document order is used as the base
URI for
resolving the relative URI into an absolute URI. If the second argument
is
omitted, then it defaults to the node in the stylesheet that contains
the
expression that includes the call to the document
function. Note that a zero-length
URI reference is a reference to the document relative to which the URI
reference is being resolved; thus document("") refers to
the
root node of the stylesheet; the tree representation of the stylesheet
is
exactly the same as if the XML document containing the stylesheet was
the
initial source document.
Two documents are treated as the same document if they are identified
by
the same URI. The URI used for the comparison is the absolute URI into
which
any relative URI was resolved and does not include any fragment
identifier.
One root node is treated as the same node as another root node if the
two
nodes are from the same document. Thus, the following expression will
always
be true:
generate-id(document("foo.xml"))=generate-id(document("foo.xml"))
The document function gives
rise
to the possibility that a node-set may contain nodes from more than one
document. With such a node-set, the relative document order of two
nodes in
the same document is the normal document order
defined by XPath [XPath]. The relative document
order
of two nodes in different documents is determined by an
implementation-dependent ordering of the documents containing the two
nodes.
There are no constraints on how the implementation orders documents
other
than that it must do so consistently: an implementation must always use
the
same order for the same set of documents.
12.2 Keys
Keys provide a way to work with documents that contain an implicit
cross-reference structure. The ID, IDREF and
IDREFS attribute types in XML provide a mechanism to allow
XML
documents to make their cross-reference explicit. XSLT supports this
through
the XPath id
function. However, this mechanism has a number of limitations:
ID attributes must be declared as such in the DTD. If an ID
attribute is declared as an ID attribute only in the external DTD
subset,
then it will be recognized as an ID attribute only if the XML
processor
reads the external DTD subset. However, XML does not require XML
processors to read the external DTD, and they may well choose not to
do
so, especially if the document is declared
standalone="yes".
A document can contain only a single set of unique IDs. There
cannot
be separate independent sets of unique IDs.
The ID of an element can only be specified in an attribute; it
cannot be specified by the content of the element, or by a child
element.
An ID is constrained to be an XML name. For example, it cannot
contain spaces.
An element can have at most one ID.
At most one element can have a particular ID.
Because of these limitations XML documents sometimes contain a
cross-reference structure that is not explicitly declared by
ID/IDREF/IDREFS
attributes.
A key is a triple containing:
the node which has the key
the name of the key (an expanded-name)
the value of the key (a string)
A stylesheet declares a set of keys for each document using the
xsl:key element. When this set of keys contains a member
with
node x, name y and value z, we say that
node
x has a key with name y and value z.
Thus, a key is a kind of generalized ID, which is not subject to the
same
limitations as an XML ID:
Keys are declared in the stylesheet using xsl:key
elements.
A key has a name as well as a value; each key name may be
thought of
as distinguishing a separate, independent space of identifiers.
The value of a named key for an element may be specified in any
convenient place; for example, in an attribute, in a child element
or in
content. An XPath expression is used to specify where to find the
value
for a particular named key.
The value of a key can be an arbitrary string; it is not
constrained
to be a name.
There can be multiple keys in a document with the same node,
same
key name, but different key values.
There can be multiple keys in a document with the same key
name,
same key value, but different nodes.
<!--
Category:
top-level-element -->
<xsl:key
name = qname
match = pattern
use = expression />
The xsl:key element is used to declare keys. The
name attribute specifies the name of the key. The value of
the
name attribute is a QName, which is
expanded as described in [2.4 Qualified Names].
The match attribute is a Pattern;
an
xsl:key element gives information about the keys of any
node
that matches the pattern specified in the match attribute. The
use attribute is an expression
specifying the values of the key; the expression is evaluated once for
each
node that matches the pattern. If the result is a node-set, then for
each
node in the node-set, the node that matches the pattern has a key of the
specified name whose value is the string-value of the node in the
node-set;
otherwise, the result is converted to a string, and the node that
matches the
pattern has a key of the specified name with value equal to that string.
Thus, a node x has a key with name y and value
z if and only if there is an xsl:key element
such
that:
x matches the pattern specified in the match
attribute of the xsl:key element;
the value of the name attribute of the
xsl:key element is equal to y; and
when the expression specified in the use attribute
of
the xsl:key element is evaluated with x as
the
current node and with a node list containing just x as
the
current node list resulting in an object u, then either
z is equal to the result of converting u to a
string as if by a call to the string
function, or u is a node-set and z is equal to
the
string-value of one or more of the nodes in u.
Note also that there may be more than one xsl:key
element
that matches a given node; all of the matching xsl:key
elements
are used, even if they do not have the same import precedence.
It is an error for the value of either the use attribute
or
the match attribute to contain a VariableReference.
Function: node-set
key(string, object)
The key function does for keys
what the
id function
does
for IDs. The first argument specifies the name of the key. The value of
the
argument must be a QName,
which is
expanded as described in [2.4 Qualified Names].
When the second argument to the key
function is of type node-set, then the result is the union of the result
of
applying the key function to the
string value of each
of the nodes in
the argument node-set. When the second argument to key is of any other type, the argument is
converted to a string as if by a call to the string
function; it
returns a node-set containing the nodes in the same document as the
context
node that have a value for the named key equal to this string.
For example, given a declaration
<xsl:key name="idkey" match="div" use="@id"/>
an expression key("idkey",@ref) will return the same
node-set
as id(@ref), assuming that the only ID attribute declared
in the
XML source document is:
<!ATTLIST div id ID #IMPLIED>
and that the ref attribute of the current node contains
no
whitespace.
Suppose a document describing a function library uses a
prototype element to define functions
<prototype name="key" return-type="node-set">
<arg type="string"/>
<arg type="object"/>
</prototype>
and a function element to refer to function names
<function>key</function>
Then the stylesheet could generate hyperlinks between the references
and
definitions as follows:
<xsl:key name="func" match="prototype" use="@name"/>
<xsl:template match="function">
<b>
<a href="#{generate-id(key('func',.))}">
<xsl:apply-templates/>
</a>
</b>
</xsl:template>
<xsl:template match="prototype">
<p><a name="{generate-id()}">
<b>Function: </b>
...
</a></p>
</xsl:template>
The key can be used to retrieve a
key
from a document other than the document containing the context node.
For
example, suppose a document contains bibliographic references in the
form
<bibref>XSLT</bibref>, and there is a separate
XML
document bib.xml containing a bibliographic database with
entries in the form:
<entry name="XSLT">...</entry>
Then the stylesheet could use the following to transform the
bibref elements:
<xsl:key name="bib" match="entry" use="@name"/>
<xsl:template match="bibref">
<xsl:variable name="name" select="."/>
<xsl:for-each select="document('bib.xml')">
<xsl:apply-templates select="key('bib',$name)"/>
</xsl:for-each>
</xsl:template>
12.3 Number Formatting
Function: string
format-number(number, string, string?)
The format-number
function
converts its first argument to a string using the format pattern string
specified by the second argument and the decimal-format named by the
third
argument, or the default decimal-format, if there is no third argument.
The
format pattern string is in the syntax specified by the JDK 1.1 DecimalFormat
class. The format pattern string is in a localized notation: the
decimal-format determines what characters have a special meaning in the
pattern (with the exception of the quote character, which is not
localized).
The format pattern must not contain the currency sign (#x00A4); support
for
this feature was added after the initial release of JDK 1.1. The
decimal-format name must be a QName, which is
expanded as described in [2.4 Qualified Names].
It is an error if the stylesheet does not contain a declaration of the
decimal-format with the specified expanded-name.
NOTE:Implementations are not required to use the JDK 1.1
implementation, nor are implementations required to be implemented in
Java.
NOTE:Stylesheets can use other facilities in XPath to control
rounding.
<!--
Category:
top-level-element -->
<xsl:decimal-format
name = qname
decimal-separator = char
grouping-separator = char
infinity = string
minus-sign = char
NaN = string
percent = char
per-mille = char
zero-digit = char
digit = char
pattern-separator = char />
The xsl:decimal-format element declares a
decimal-format,
which controls the interpretation of a format pattern used by the format-number function. If there
is a
name attribute, then the element declares a named
decimal-format; otherwise, it declares the default decimal-format. The
value
of the name attribute is a QName, which is
expanded as described in [2.4 Qualified Names].
It is an error to declare either the default decimal-format or a
decimal-format with a given name more than once (even with different import precedence), unless it is
declared
every time with the same value for all attributes (taking into account
any
default values).
The other attributes on xsl:decimal-format correspond to
the
methods on the JDK 1.1 DecimalFormatSymbols
class. For each get/set method pair there is
an
attribute defined for the xsl:decimal-format element.
The following attributes both control the interpretation of
characters in
the format pattern and specify characters that may appear in the result
of
formatting the number:
decimal-separator specifies the character used for
the
decimal sign; the default value is the period character
(.)
grouping-separator specifies the character used as
a
grouping (e.g. thousands) separator; the default value is the comma
character (,)
percent specifies the character used as a percent
sign;
the default value is the percent character (%)
per-mille specifies the character used as a per
mille
sign; the default value is the Unicode per-mille character (#x2030)
zero-digit specifies the character used as the
digit
zero; the default value is the digit zero (0)
The following attributes control the interpretation of characters in
the
format pattern:
digit specifies the character used for a digit in
the
format pattern; the default value is the number sign character
(#)
pattern-separator specifies the character used to
separate positive and negative sub patterns in a pattern; the
default
value is the semi-colon character (;)
The following attributes specify characters or strings that may
appear in
the result of formatting the number:
infinity specifies the string used to represent
infinity; the default value is the string Infinity
NaN specifies the string used to represent the NaN
value; the default value is the string NaN
minus-sign specifies the character used as the
default
minus sign; the default value is the hyphen-minus character
(-, #x2D)
12.4 Miscellaneous Additional Functions
Function: node-set
current()
The current function returns a
node-set that has the current node as its
only
member. For an outermost expression (an expression not occurring within
another expression), the current node is always the same as the context
node.
Thus,
<xsl:value-of select="current()"/>
means the same as
<xsl:value-of select="."/>
However, within square brackets the current node is usually different
from
the context node. For example,
<xsl:apply-templates select="//glossary/item[@name=current()/@ref]"/>
will process all item elements that have a
glossary parent element and that have a name
attribute with value equal to the value of the current node's
ref attribute. This is different from
<xsl:apply-templates select="//glossary/item[@name=./@ref]"/>
which means the same as
<xsl:apply-templates select="//glossary/item[@name=@ref]"/>
and so would process all item elements that have a
glossary parent element and that have a name
attribute and a ref attribute with the same value.
It is an error to use the current
function in a pattern.
Function: string
unparsed-entity-uri(string)
The unparsed-entity-uri
returns the URI of the unparsed entity with the specified name in the
same
document as the context node (see [3.3
Unparsed Entities]). It returns the empty string if there is no
such
entity.
Function: string
generate-id(node-set?)
The generate-id function
returns a string that uniquely identifies the node in the argument
node-set
that is first in document order. The unique identifier must consist of
ASCII
alphanumeric characters and must start with an alphabetic character.
Thus,
the string is syntactically an XML name. An implementation is free to
generate an identifier in any convenient way provided that it always
generates the same identifier for the same node and that different
identifiers are always generated from different nodes. An implementation
is
under no obligation to generate the same identifiers each time a
document is
transformed. There is no guarantee that a generated unique identifier
will
be distinct from any unique IDs specified in the source document. If
the
argument node-set is empty, the empty string is returned. If the
argument is
omitted, it defaults to the context node.
Function: object
system-property(string)
The argument must evaluate to a string that is a QName. The QName is expanded
into
a name using the namespace declarations in scope for the expression. The
system-property function
returns an object representing the value of the system property
identified by
the name. If there is no such system property, the empty string should
be
returned.
Implementations must provide the following system properties, which
are
all in the XSLT namespace:
xsl:version, a number giving the version of XSLT
implemented by the processor; for XSLT processors implementing the
version of XSLT specified by this document, this is the number 1.0xsl:vendor, a string identifying the vendor of the
XSLT
processorxsl:vendor-url, a string containing a URL identifying
the
vendor of the XSLT processor; typically this is the host page (home
page)
of the vendor's Web site.
13 Messages
<!--
Category: instruction -->
<xsl:message
terminate = "yes" | "no">
<!-- Content: template -->
</xsl:message>
The xsl:message instruction sends a message in a way
that is
dependent on the XSLT processor. The content of the xsl:message
instruction is a template. The xsl:message is instantiated
by
instantiating the content to create an XML fragment. This XML fragment
is
the content of the message.
NOTE:An XSLT processor might implement xsl:message
by
popping up an alert box or by writing to a log file.
If the terminate attribute has the value yes,
then the XSLT processor should terminate processing after sending the
message. The default value is no.
One convenient way to do localisation is to put the localized
information
(message text, etc.) in an XML document, which becomes an additional
input
file to the stylesheet. For example, suppose messages for a language
L are stored in an XML file
resources/L.xml in the form:
<messages>
<message name="problem">A problem was detected.</message>
<message name="error">An error was detected.</message>
</messages>
Then a stylesheet could use the following approach to localize
messages:
<xsl:param name="lang" select="en"/>
<xsl:variable name="messages"
select="document(concat('resources/', $lang, '.xml'))/messages"/>
<xsl:template name="localized-message">
<xsl:param name="name"/>
<xsl:message>
<xsl:value-of select="$messages/message[@name=$name]"/>
</xsl:message>
</xsl:template>
<xsl:template name="problem">
<xsl:call-template name="localized-message"/>
<xsl:with-param name="name">problem</xsl:with-param>
</xsl:call-template>
</xsl:template>
14 Extensions
XSLT allows two kinds of extension, extension elements and extension
functions.
This version of XSLT does not provide a mechanism for defining
implementations of extensions. Therefore, an XSLT stylesheet that must
be
portable between XSLT implementations cannot rely on particular
extensions
being available. XSLT provides mechanisms that allow an XSLT stylesheet
to
determine whether the XSLT processor by which it is being processed has
implementations of particular extensions available, and to specify what
should happen if those extensions are not available. If an XSLT
stylesheet
is careful to make use of these mechanisms, it is possible for it to
take
advantage of extensions and still work with any XSLT implementation.
14.1 Extension Elements
The element extension mechanism
allows namespaces to be designated as extension namespaces. When a
namespace is designated as an extension namespace and an element with a
name
from that namespace occurs in a template, then the element is treated as
an
instruction rather than as a literal result element. The namespace
determines
the semantics of the instruction.
NOTE:Since an element that is a child of an
xsl:stylesheet element is not occurring in a template,
non-XSLT top-level elements are not
extension
elements as defined here, and nothing in this section applies to
them.
A namespace is designated as an extension namespace by using an
extension-element-prefixes attribute on an
xsl:stylesheet element or an
xsl:extension-element-prefixes attribute on a literal
result
element or extension element. The value of both these attributes is a
whitespace-separated list of namespace prefixes. The namespace bound to
each
of the prefixes is designated as an extension namespace. It is an error
if
there is no namespace bound to the prefix on the element bearing the
extension-element-prefixes or
xsl:extension-element-prefixes attribute. The default
namespace
(as declared by xmlns) may be designated as an extension
namespace by including #default in the list of namespace
prefixes. The designation of a namespace as an extension namespace is
effective within the subtree of the stylesheet rooted at the element
bearing
the extension-element-prefixes or
xsl:extension-element-prefixes attribute; a subtree rooted
at an
xsl:stylesheet element does not include any stylesheets
imported
or included by children of that xsl:stylesheet element.
If the XSLT processor does not have an implementation of a particular
extension element available, then the element-available function
must
return false for the name of the element. When such an extension
element is
instantiated, then the XSLT processor must perform fallback for the
element
as specified in [15 Fallback]. An XSLT
processor must not signal an error merely because a template contains an
extension element for which no implementation is available.
If the XSLT processor has an implementation of a particular extension
element available, then the element-available
function must
return true for the name of the element.
14.2 Extension Functions
If a FunctionName
in a FunctionCall
expression is not an NCName (i.e. if
it
contains a colon), then it is treated as a call to an extension
function.
The FunctionName
is
expanded to a name using the namespace declarations from the evaluation
context.
If the XSLT processor does not have an implementation of an extension
function of a particular name available, then the function-available function
must
return false for that name. If such an extension function occurs in an
expression and the extension function is actually called, the XSLT
processor
must signal an error. An XSLT processor must not signal an error merely
because an expression contains an extension function for which no
implementation is available.
If the XSLT processor has an implementation of an extension function
of a
particular name available, then the function-available function
must
return true for that name. If such an extension is called, then the XSLT
processor must call the implementation passing it the function call
arguments; the result returned by the implementation is returned as the
result of the function call.
15 Fallback
<!--
Category: instruction -->
<xsl:fallback>
<!-- Content: template -->
</xsl:fallback>
Normally, instantiating an xsl:fallback element does
nothing.
However, when an XSLT processor performs fallback for an instruction
element, if the instruction element has one or more xsl:fallback
children, then the content of each of the xsl:fallback
children
must be instantiated in sequence; otherwise, an error must be signaled.
The
content of an xsl:fallback element is a template.
The following functions can be used with the xsl:choose
and
xsl:if instructions to explicitly control how a stylesheet
should behave if particular elements or functions are not available.
Function: boolean
element-available(string)
The argument must evaluate to a string that is a QName. The QName is expanded
into
an expanded-name
using the namespace declarations in scope for the expression. The element-available function
returns
true if and only if the expanded-name is the name of an instruction. If
the
expanded-name has a namespace URI equal to the XSLT namespace URI, then
it
refers to an element defined by XSLT. Otherwise, it refers to an
extension
element. If the expanded-name has a null namespace URI, the element-available function
will
return false.
Function: boolean
function-available(string)
The argument must evaluate to a string that is a QName. The QName is expanded
into
an expanded-name
using the namespace declarations in scope for the expression. The function-available function
returns true if and only if the expanded-name is the name of a function
in
the function library. If the expanded-name has a non-null namespace URI,
then
it refers to an extension function; otherwise, it refers to a function
defined by XPath or XSLT.
16 Output
<!--
Category: top-level-element -->
<xsl:output
method = "xml" | "html" | "text" |
qname-but-not-ncname
version = nmtoken
encoding = string
omit-xml-declaration = "yes" | "no"
standalone = "yes" | "no"
doctype-public = string
doctype-system = string
cdata-section-elements = qnames
indent = "yes" | "no"
media-type = string />
An XSLT processor may output the result tree as a sequence of bytes,
although it is not required to be able to do so (see [17 Conformance]). The xsl:output
element allows stylesheet authors to specify how they wish the result
tree to
be output. If an XSLT processor outputs the result tree, it should do so
as
specified by the xsl:output element; however, it is not
required
to do so.
The xsl:output element is only allowed as a top-level element.
The method attribute on xsl:output
identifies
the overall method that should be used for outputting the result tree.
The
value must be a QName.
If the QName
does not have a
prefix, then it identifies a method specified in this document and must
be
one of xml, html or text. If the
QName has a
prefix,
then the QName
is
expanded into an expanded-name
as
described in [2.4 Qualified Names]; the
expanded-name identifies the output method; the behavior in this case is
not
specified by this document.
The default for the method attribute is chosen as
follows.
If
the root node of the result tree has an element child,
the expanded-name of the first element child of the root node
(i.e.
the document element) of the result tree has local part html
(in any combination of upper and lower case) and a null namespace
URI,
and
any text nodes preceding the first element child of the root
node of
the result tree contain only whitespace characters,
then the default output method is html; otherwise, the
default output method is xml. The default output method
should
be used if there are no xsl:output elements or if none of
the
xsl:output elements specifies a value for the
method attribute.
The other attributes on xsl:output provide parameters
for the
output method. The following attributes are allowed:
version specifies the version of the output method
indent specifies whether the XSLT processor may
add
additional whitespace when outputting the result tree; the value
must be
yes or no
encoding specifies the preferred character
encoding
that the XSLT processor should use to encode sequences of characters
as
sequences of bytes; the value of the attribute should be treated
case-insensitively; the value must contain only characters in the
range
#x21 to #x7E (i.e. printable ASCII characters); the value should
either
be a charset registered with the Internet Assigned
Numbers
Authority [IANA], [RFC2278]
or
start with X-
media-type specifies the media type (MIME content
type)
of the data that results from outputting the result tree; the
charset parameter should not be specified explicitly;
instead, when the top-level media type is text, a
charset parameter should be added according to the
character
encoding actually used by the output method
doctype-system specifies the system identifier to
be
used in the document type declaration
doctype-public specifies the public identifier to
be
used in the document type declaration
omit-xml-declaration specifies whether the XSLT
processor should output an XML declaration; the value must be
yes or no
standalone specifies whether the XSLT processor
should
output a standalone document declaration; the value must be
yes or no
cdata-section-elements specifies a list of the
names of
elements whose text node children should be output using CDATA
sections
The detailed semantics of each attribute will be described separately
for
each output method for which it is applicable. If the semantics of an
attribute are not described for an output method, then it is not
applicable
to that output method.
A stylesheet may contain multiple xsl:output elements
and may
include or import stylesheets that also contain xsl:output
elements. All the xsl:output elements occurring in a
stylesheet
are merged into a single effective xsl:output element. For
the
cdata-section-elements attribute, the effective value is
the
union of the specified values. For other attributes, the effective
value is
the specified value with the highest import
precedence. It is an error if there is more than one such value for
an
attribute. An XSLT processor may signal the error; if it does not
signal the
error, if should recover by using the value that occurs last in the
stylesheet. The values of attributes are defaulted after the
xsl:output elements have been merged; different output
methods
may have different default values for an attribute.
16.1 XML Output Method
The xml output method outputs the result tree as a
well-formed XML external general parsed entity. If the root node of the
result tree has a single element node child and no text node children,
then
the entity should also be a well-formed XML document entity. When the
entity
is referenced within a trivial XML document wrapper like this
<!DOCTYPE doc [
<!ENTITY e SYSTEM "entity-URI">
]>
<doc>&e;</doc>
where entity-URI is a URI for the entity,
then the
wrapper document as a whole should be a well-formed XML document
conforming
to the XML Namespaces Recommendation [XML Names].
In
addition, the output should be such that if a new tree was constructed
by
parsing the wrapper as an XML document as specified in [3 Data Model], and then removing the
document
element, making its children instead be children of the root node, then
the
new tree would be the same as the result tree, with the following
possible
exceptions:
If the XSLT processor generated a document type declaration because
of the
doctype-system attribute, then the above requirements apply
to
the entity with the generated document type declaration removed.
The version attribute specifies the version of XML to be
used
for outputting the result tree. If the XSLT processor does not support
this
version of XML, it should use a version of XML that it does support.
The
version output in the XML declaration (if an XML declaration is output)
should correspond to the version of XML that the processor used for
outputting the result tree. The value of the version
attribute
should match the VersionNum
production
of the XML Recommendation [XML]. The default value is
1.0.
The encoding attribute specifies the preferred encoding
to
use for outputting the result tree. XSLT processors are required to
respect
values of UTF-8 and UTF-16. For other values,
if
the XSLT processor does not support the specified encoding it may signal
an
error; if it does not signal an error it should use UTF-8
or
UTF-16 instead. The XSLT processor must not use an
encoding
whose name does not match the EncName production of
the
XML Recommendation [XML]. If no encoding
attribute is specified, then the XSLT processor should use either
UTF-8 or UTF-16. It is possible that the
result
tree will contain a character that cannot be represented in the encoding
that
the XSLT processor is using for output. In this case, if the character
occurs in a context where XML recognizes character references (i.e. in
the
value of an attribute node or text node), then the character should be
output
as a character reference; otherwise (for example if the character occurs
in
the name of an element) the XSLT processor should signal an error.
If the indent attribute has the value yes,
then
the xml output method may output whitespace in addition to
the
whitespace in the result tree (possibly based on whitespace stripped
from
either the source document or the stylesheet) in order to indent the
result
nicely; if the indent attribute has the value no,
it should not output any additional whitespace. The default value is
no. The xml output method should use an
algorithm
to output additional whitespace that ensures that the result if
whitespace
were to be stripped from the output using the process described in [3.4 Whitespace Stripping] with the set of
whitespace-preserving elements consisting of just xsl:text
would
be the same when additional whitespace is output as when additional
whitespace is not output.
NOTE:It is usually not safe to use indent="yes"
with
document types that include element types with mixed content.
The cdata-section-elements attribute contains a
whitespace-separated list of QNames. Each QName is expanded
into
an expanded-name using the namespace declarations in effect on the
xsl:output element in which the QName occurs; if
there
is a default namespace, it is used for QNames that do
not
have a prefix. The expansion is performed before the merging of
multiple
xsl:output elements into a single effective
xsl:output element. If the expanded-name of the parent of a
text
node is a member of the list, then the text node should be output as a
CDATA
section. For example,
<xsl:output cdata-section-elements="example"/>
would cause a literal result element written in the stylesheet as
<example><foo></example>
or as
<example><![CDATA[<foo>]]></example>
to be output as
<example><![CDATA[<foo>]]></example>
If the text node contains the sequence of characters ]]>,
then the currently open CDATA section should be closed following the
]] and a new CDATA section opened before the >.
For example, a literal result element written in the stylesheet as
<example>]]></example>
would be output as
<example><![CDATA[]]]]><![CDATA[>]]></example>
If the text node contains a character that is not representable in
the
character encoding being used to output the result tree, then the
currently
open CDATA section should be closed before the character, the character
should be output using a character reference or entity reference, and a
new
CDATA section should be opened for any further characters in the text
node.
CDATA sections should not be used except for text nodes that the
cdata-section-elements attribute explicitly specifies
should be
output using CDATA sections.
The xml output method should output an XML declaration
unless
the omit-xml-declaration attribute has the value
yes. The XML declaration should include both version
information
and an encoding declaration. If the standalone attribute is
specified, it should include a standalone document declaration with the
same
value as the value as the value of the standalone
attribute.
Otherwise, it should not include a standalone document declaration; this
ensures that it is both a XML declaration (allowed at the beginning of a
document entity) and a text declaration (allowed at the beginning of an
external general parsed entity).
If the doctype-system attribute is specified, the
xml output method should output a document type declaration
immediately before the first element. The name following
<!DOCTYPE should be the name of the first element. If
doctype-public attribute is also specified, then the
xml output method should output PUBLIC
followed by
the public identifier and then the system identifier; otherwise, it
should
output SYSTEM followed by the system identifier. The
internal
subset should be empty. The doctype-public attribute
should be
ignored unless the doctype-system attribute is specified.
The media-type attribute is applicable for the
xml output method. The default value for the
media-type attribute is text/xml.
16.2 HTML Output Method
The html output method outputs the result tree as HTML;
for
example,
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html"/>
<xsl:template match="/">
<html>
<xsl:apply-templates/>
</html>
</xsl:template>
...
</xsl:stylesheet>
The version attribute indicates the version of the HTML.
The
default value is 4.0, which specifies that the result
should be
output as HTML conforming to the HTML 4.0 Recommendation [HTML].
The html output method should not output an element
differently from the xml output method unless the
expanded-name
of the element has a null namespace URI; an element whose expanded-name
has a
non-null namespace URI should be output as XML. If the expanded-name of
the
element has a null namespace URI, but the local part of the
expanded-name is
not recognized as the name of an HTML element, the element should output
in
the same way as a non-empty, inline element such as span.
The html output method should not output an end-tag for
empty
elements. For HTML 4.0, the empty elements are area,
base, basefont, br, col,
frame, hr, img, input,
isindex, link, meta and
param. For example, an element written as
<br/> or <br></br> in the
stylesheet should be output as <br>.
The html output method should recognize the names of
HTML
elements regardless of case. For example, elements named br,
BR or Br should all be recognized as the HTML
br element and output without an end-tag.
The html output method should not perform escaping for
the
content of the script and style elements. For
example, a literal result element written in the stylesheet as
<script>if (a < b) foo()</script>
or
<script><![CDATA[if (a < b) foo()]]></script>
should be output as
<script>if (a < b) foo()</script>
The html output method should not escape <
characters occurring in attribute values.
If the indent attribute has the value yes,
then
the html output method may add or remove whitespace as it
outputs the result tree, so long as it does not change how an HTML user
agent
would render the output. The default value is yes.
The html output method should escape non-ASCII
characters in
URI attribute values using the method recommended in Section
B.2.1 of the HTML 4.0 Recommendation.
The html output method may output a character using a
character entity reference, if one is defined for it in the version of
HTML
that the output method is using.
The html output method should terminate processing
instructions with > rather than ?>.
The html output method should output boolean attributes
(that
is attributes with only a single allowed value that is equal to the name
of
the attribute) in minimized form. For example, a start-tag written in
the
stylesheet as
<OPTION selected="selected">
should be output as
<OPTION selected>
The html output method should not escape a &
character occurring in an attribute value immediately followed by a
{ character (see Section
B.7.1 of the HTML 4.0 Recommendation). For example, a start-tag
written
in the stylesheet as
<BODY bgcolor='&{{randomrbg}};'>
should be output as
<BODY bgcolor='&{randomrbg};'>
The encoding attribute specifies the preferred encoding
to be
used. If there is a HEAD element, then the html
output method should add a META element immediately after
the
start-tag of the HEAD element specifying the character
encoding
actually used. For example,
<HEAD>
<META http-equiv="content-type" content="text/html; charset=EUC-JP">
...
It is possible that the result tree will contain a character that
cannot
be represented in the encoding that the XSLT processor is using for
output.
In this case, if the character occurs in a context where HTML recognizes
character references, then the character should be output as a character
entity reference or decimal numeric character reference; otherwise (for
example, in a script or style element or in a
comment), the XSLT processor should signal an error.
If the doctype-public or doctype-system
attributes are specified, then the html output method
should
output a document type declaration immediately before the first element.
The
name following <!DOCTYPE should be HTML or
html. If the doctype-public attribute is
specified, then the output method should output PUBLIC
followed
by the specified public identifier; if the doctype-system
attribute is also specified, it should also output the specified system
identifier following the public identifier. If the
doctype-system attribute is specified but the
doctype-public attribute is not specified, then the output
method should output SYSTEM followed by the specified
system
identifier.
The media-type attribute is applicable for the
html output method. The default value is
text/html.
16.3 Text Output Method
The text output method outputs the result tree by
outputting
the string-value of every text node in the result tree in document order
without any escaping.
The media-type attribute is applicable for the
text output method. The default value for the
media-type attribute is text/plain.
The encoding attribute identifies the encoding that the
text output method should use to convert sequences of
characters
to sequences of bytes. The default is system-dependent. If the result
tree
contains a character that cannot be represented in the encoding that the
XSLT
processor is using for output, the XSLT processor should signal an
error.
16.4 Disabling Output Escaping
Normally, the xml output method escapes & and <
(and
possibly other characters) when outputting text nodes. This ensures
that the
output is well-formed XML. However, it is sometimes convenient to be
able to
produce output that is almost, but not quite well-formed XML; for
example,
the output may include ill-formed sections which are intended to be
transformed into well-formed XML by a subsequent non-XML aware process.
For
this reason, XSLT provides a mechanism for disabling output escaping. An
xsl:value-of or xsl:text element may have a
disable-output-escaping attribute; the allowed values are
yes or no; the default is no; if
the
value is yes, then a text node generated by instantiating
the
xsl:value-of or xsl:text element should be
output
without any escaping. For example,
<xsl:text disable-output-escaping="yes"><</xsl:text>
should generate the single character <.
It is an error for output escaping to be disabled for a text node
that is
used for something other than a text node in the result tree. Thus, it
is an
error to disable output escaping for an xsl:value-of or
xsl:text element that is used to generate the string-value
of a
comment, processing instruction or attribute node; it is also an error
to
convert a result tree fragment to
a
number or a string if the result tree fragment contains a text node for
which
escaping was disabled. In both cases, an XSLT processor may signal the
error; if it does not signal the error, it must recover by ignoring the
disable-output-escaping attribute.
The disable-output-escaping attribute may be used with
the
html output method as well as with the xml
output
method. The text output method ignores the
disable-output-escaping attribute, since it does not
perform any
output escaping.
An XSLT processor will only be able to disable output escaping if it
controls how the result tree is output. This may not always be the case.
For
example, the result tree may be used as the source tree for another XSLT
transformation instead of being output. An XSLT processor is not
required to
support disabling output escaping. If an xsl:value-of or
xsl:text specifies that output escaping should be disabled
and
the XSLT processor does not support this, the XSLT processor may signal
an
error; if it does not signal an error, it must recover by not disabling
output escaping.
If output escaping is disabled for a character that is not
representable
in the encoding that the XSLT processor is using for output, then the
XSLT
processor may signal an error; if it does not signal an error, it must
recover by not disabling output escaping.
Since disabling output escaping may not work with all XSLT processors
and
can result in XML that is not well-formed, it should be used only when
there
is no alternative.
17 Conformance
A conforming XSLT processor must be able to use a stylesheet to
transform
a source tree into a result tree as specified in this document. A
conforming
XSLT processor need not be able to output the result in XML or in any
other
form.
NOTE:Vendors of XSLT processors are strongly encouraged to
provide a
way to verify that their processor is behaving conformingly by
allowing the
result tree to be output as XML or by providing access to the result
tree
through a standard API such as the DOM or SAX.
A conforming XSLT processor must signal any errors except for those
that
this document specifically allows an XSLT processor not to signal. A
conforming XSLT processor may but need not recover from any errors that
it
signals.
A conforming XSLT processor may impose limits on the processing
resources
consumed by the processing of a stylesheet.
18 Notation
The specification of each XSLT-defined element type is preceded by a
summary of its syntax in the form of a model for elements of that
element
type. The meaning of syntax summary notation is as follows:
An attribute is required if and only if its name is in bold.
The string that occurs in the place of an attribute value
specifies
the allowed values of the attribute. If this is surrounded by curly
braces, then the attribute value is treated as an attribute value template, and
the
string occurring within curly braces specifies the allowed values of
the
result of instantiating the attribute value template. Alternative
allowed
values are separated by |. A quoted string indicates a
value equal to that specific string. An unquoted, italicized name
specifies a particular type of value.
If the element is allowed not to be empty, then the element
contains
a comment specifying the allowed content. The allowed content is
specified in a similar way to an element type declaration in XML;
template means that any mixture of text nodes, literal result
elements, extension elements, and XSLT elements from the
instruction category is allowed; top-level-elements
means that any mixture of XSLT elements from the
top-level-element category is allowed.
The element is prefaced by comments indicating if it belongs to
the
instruction category or top-level-element
category or both. The category of an element just affects whether
it is
allowed in the content of elements that allow a template or
top-level-elements.
A References
A.1 Normative References
- XML
- World Wide Web Consortium. Extensible Markup Language (XML)
1.0. W3C Recommendation. See http://www.w3.org/TR/1998/REC-xml-19980210
- XML Names
- World Wide Web Consortium. Namespaces in XML. W3C
Recommendation. See http://www.w3.org/TR/REC-xml-names
- XPath
- World Wide Web Consortium. XML Path Language. W3C
Recommendation. See http://www.w3.org/TR/xpath
A.2 Other References
- CSS2
- World Wide Web Consortium. Cascading Style Sheets, level 2
(CSS2). W3C Recommendation. See http://www.w3.org/TR/1998/REC-CSS2-19980512
- DSSSL
- International Organization for Standardization, International
Electrotechnical Commission. ISO/IEC 10179:1996. Document
Style
Semantics and Specification Language (DSSSL). International
Standard.
- HTML
- World Wide Web Consortium. HTML 4.0 specification. W3C
Recommendation. See http://www.w3.org/TR/REC-html40
- IANA
- Internet Assigned Numbers Authority. Character Sets. See ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets.
- RFC2278
- N. Freed, J. Postel. IANA Charset Registration Procedures.
IETF RFC 2278. See http://www.ietf.org/rfc/rfc2278.txt.
- RFC2376
- E. Whitehead, M. Murata. XML Media Types. IETF RFC 2376.
See
http://www.ietf.org/rfc/rfc2376.txt.
- RFC2396
- T. Berners-Lee, R. Fielding, and L. Masinter. Uniform
Resource
Identifiers (URI): Generic Syntax. IETF RFC 2396. See http://www.ietf.org/rfc/rfc2396.txt.
- UNICODE TR10
- Unicode Consortium. Unicode Technical Report #10. Unicode
Collation Algorithm. Unicode Technical Report. See http://www.unicode.org/unicode/reports/tr10/index.html.
- XHTML
- World Wide Web Consortium. XHTML 1.0: The Extensible
HyperText
Markup Language. W3C Proposed Recommendation. See http://www.w3.org/TR/xhtml1
- XPointer
- World Wide Web Consortium. XML Pointer Language (XPointer).
W3C Working Draft. See http://www.w3.org/TR/xptr
- XML Stylesheet
- World Wide Web Consortium. Associating stylesheets with XML
documents. W3C Recommendation. See http://www.w3.org/TR/xml-stylesheet
- XSL
- World Wide Web Consortium. Extensible Stylesheet Language
(XSL). W3C Working Draft. See http://www.w3.org/TR/WD-xsl
B Element Syntax Summary
<!-- Category: instruction
-->
<xsl:apply-imports />
<!-- Category: instruction
-->
<xsl:apply-templates
select = node-set-expression
mode = qname>
<!-- Content: (xsl:sort | xsl:with-param)* -->
</xsl:apply-templates>
<!-- Category: instruction
-->
<xsl:attribute
name = { qname }
namespace = { uri-reference }>
<!-- Content: template -->
</xsl:attribute>
<!-- Category:
top-level-element
-->
<xsl:attribute-set
name = qname
use-attribute-sets = qnames>
<!-- Content: xsl:attribute*
-->
</xsl:attribute-set>
<!-- Category: instruction
-->
<xsl:call-template
name = qname>
<!-- Content: xsl:with-param*
-->
</xsl:call-template>
<!-- Category: instruction
-->
<xsl:choose>
<!-- Content: (xsl:when+, xsl:otherwise?) -->
</xsl:choose>
<!-- Category: instruction
-->
<xsl:comment>
<!-- Content: template -->
</xsl:comment>
<!-- Category: instruction
-->
<xsl:copy
use-attribute-sets = qnames>
<!-- Content: template -->
</xsl:copy>
<!-- Category: instruction
-->
<xsl:copy-of
select = expression />
<!-- Category:
top-level-element
-->
<xsl:decimal-format
name = qname
decimal-separator = char
grouping-separator = char
infinity = string
minus-sign = char
NaN = string
percent = char
per-mille = char
zero-digit = char
digit = char
pattern-separator = char />
<!-- Category: instruction
-->
<xsl:element
name = { qname }
namespace = { uri-reference }
use-attribute-sets = qnames>
<!-- Content: template -->
</xsl:element>
<!-- Category: instruction
-->
<xsl:fallback>
<!-- Content: template -->
</xsl:fallback>
<!-- Category: instruction
-->
<xsl:for-each
select = node-set-expression>
<!-- Content: (xsl:sort*,
template) -->
</xsl:for-each>
<!-- Category: instruction
-->
<xsl:if
test = boolean-expression>
<!-- Content: template -->
</xsl:if>
<xsl:import
href = uri-reference />
<!-- Category:
top-level-element
-->
<xsl:include
href = uri-reference />
<!-- Category:
top-level-element
-->
<xsl:key
name = qname
match = pattern
use = expression />
<!-- Category: instruction
-->
<xsl:message
terminate = "yes" | "no">
<!-- Content: template -->
</xsl:message>
<!-- Category:
top-level-element
-->
<xsl:namespace-alias
stylesheet-prefix = prefix | "#default"
result-prefix = prefix |
"#default" />
<!-- Category: instruction
-->
<xsl:number
level = "single" | "multiple" | "any"
count = pattern
from = pattern
value = number-expression
format = { string }
lang = { nmtoken }
letter-value = { "alphabetic" | "traditional" }
grouping-separator = { char }
grouping-size = { number } />
<xsl:otherwise>
<!-- Content: template -->
</xsl:otherwise>
<!-- Category:
top-level-element
-->
<xsl:output
method = "xml" | "html" | "text" |
qname-but-not-ncname
version = nmtoken
encoding = string
omit-xml-declaration = "yes" | "no"
standalone = "yes" | "no"
doctype-public = string
doctype-system = string
cdata-section-elements = qnames
indent = "yes" | "no"
media-type = string />
<!-- Category:
top-level-element
-->
<xsl:param
name = qname
select = expression>
<!-- Content: template -->
</xsl:param>
<!-- Category:
top-level-element
-->
<xsl:preserve-space
elements = tokens />
<!-- Category: instruction
-->
<xsl:processing-instruction
name = { ncname }>
<!-- Content: template -->
</xsl:processing-instruction>
<xsl:sort
select = string-expression
lang = { nmtoken }
data-type = { "text" | "number" | qname-but-not-ncname
}
order = { "ascending" | "descending" }
case-order = { "upper-first" | "lower-first"
} />
<!-- Category:
top-level-element
-->
<xsl:strip-space
elements = tokens />
<xsl:stylesheet
id = id
extension-element-prefixes = tokens
exclude-result-prefixes = tokens
version = number>
<!-- Content: (xsl:import*,
top-level-elements) -->
</xsl:stylesheet>
<!-- Category:
top-level-element
-->
<xsl:template
match = pattern
name = qname
priority = number
mode = qname>
<!-- Content: (xsl:param*,
template) -->
</xsl:template>
<!-- Category: instruction
-->
<xsl:text
disable-output-escaping = "yes" | "no">
<!-- Content: #PCDATA -->
</xsl:text>
<xsl:transform
id = id
extension-element-prefixes = tokens
exclude-result-prefixes = tokens
version = number>
<!-- Content: (xsl:import*,
top-level-elements) -->
</xsl:transform>
<!-- Category: instruction
-->
<xsl:value-of
select = string-expression
disable-output-escaping = "yes" | "no" />
<!-- Category:
top-level-element
-->
<!-- Category: instruction -->
<xsl:variable
name = qname
select = expression>
<!-- Content: template -->
</xsl:variable>
<xsl:when
test = boolean-expression>
<!-- Content: template -->
</xsl:when>
<xsl:with-param
name = qname
select = expression>
<!-- Content: template -->
</xsl:with-param>
C DTD Fragment for XSLT Stylesheets
(Non-Normative)
NOTE:This DTD Fragment is not normative because XML 1.0 DTDs do
not
support XML Namespaces and thus cannot correctly describe the allowed
structure of an XSLT stylesheet.
The following entity can be used to construct a DTD for XSLT
stylesheets
that create instances of a particular result DTD. Before referencing
the
entity, the stylesheet DTD must define a result-elements
parameter entity listing the allowed result element types. For example:
<!ENTITY % result-elements "
| fo:inline-sequence
| fo:block
">
Such result elements should be declared to have
xsl:use-attribute-sets and
xsl:extension-element-prefixes attributes. The following
entity
declares the result-element-atts parameter for this
purpose. The
content that XSLT allows for result elements is the same as it allows
for the
XSLT elements that are declared in the following entity with a content
model
of %template;. The DTD may use a more restrictive content
model
than %template; to reflect the constraints of the result
DTD.
The DTD may define the non-xsl-top-level parameter
entity to
allow additional top-level elements from namespaces other than the XSLT
namespace.
The use of the xsl: prefix in this DTD does not imply
that
XSLT stylesheets are required to use this prefix. Any of the elements
declared in this DTD may have attributes whose name starts with
xmlns: or is equal to xmlns in addition to the
attributes declared in this DTD.
<!ENTITY % char-instructions "
| xsl:apply-templates
| xsl:call-template
| xsl:apply-imports
| xsl:for-each
| xsl:value-of
| xsl:copy-of
| xsl:number
| xsl:choose
| xsl:if
| xsl:text
| xsl:copy
| xsl:variable
| xsl:message
| xsl:fallback
">
<!ENTITY % instructions "
%char-instructions;
| xsl:processing-instruction
| xsl:comment
| xsl:element
| xsl:attribute
">
<!ENTITY % char-template "
(#PCDATA
%char-instructions;)*
">
<!ENTITY % template "
(#PCDATA
%instructions;
%result-elements;)*
">
<!-- Used for the type of an attribute value that is a URI reference.-->
<!ENTITY % URI "CDATA">
<!-- Used for the type of an attribute value that is a pattern.-->
<!ENTITY % pattern "CDATA">
<!-- Used for the type of an attribute value that is an
attribute value template.-->
<!ENTITY % avt "CDATA">
<!-- Used for the type of an attribute value that is a QName; the prefix
gets expanded by the XSLT processor. -->
<!ENTITY % qname "NMTOKEN">
<!-- Like qname but a whitespace-separated list of QNames. -->
<!ENTITY % qnames "NMTOKENS">
<!-- Used for the type of an attribute value that is an expression.-->
<!ENTITY % expr "CDATA">
<!-- Used for the type of an attribute value that consists
of a single character.-->
<!ENTITY % char "CDATA">
<!-- Used for the type of an attribute value that is a priority. -->
<!ENTITY % priority "NMTOKEN">
<!ENTITY % space-att "xml:space (default|preserve) #IMPLIED">
<!-- This may be overridden to customize the set of elements allowed
at the top-level. -->
<!ENTITY % non-xsl-top-level "">
<!ENTITY % top-level "
(xsl:import*,
(xsl:include
| xsl:strip-space
| xsl:preserve-space
| xsl:output
| xsl:key
| xsl:decimal-format
| xsl:attribute-set
| xsl:variable
| xsl:param
| xsl:template
| xsl:namespace-alias
%non-xsl-top-level;)*)
">
<!ENTITY % top-level-atts '
extension-element-prefixes CDATA #IMPLIED
exclude-result-prefixes CDATA #IMPLIED
id ID #IMPLIED
version NMTOKEN #REQUIRED
xmlns:xsl CDATA #FIXED "http://www.w3.org/1999/XSL/Transform"
%space-att;
'>
<!-- This entity is defined for use in the ATTLIST declaration
for result elements. -->
<!ENTITY % result-element-atts '
xsl:extension-element-prefixes CDATA #IMPLIED
xsl:exclude-result-prefixes CDATA #IMPLIED
xsl:use-attribute-sets %qnames; #IMPLIED
xsl:version NMTOKEN #IMPLIED
'>
<!ELEMENT xsl:stylesheet %top-level;>
<!ATTLIST xsl:stylesheet %top-level-atts;>
<!ELEMENT xsl:transform %top-level;>
<!ATTLIST xsl:transform %top-level-atts;>
<!ELEMENT xsl:import EMPTY>
<!ATTLIST xsl:import href %URI; #REQUIRED>
<!ELEMENT xsl:include EMPTY>
<!ATTLIST xsl:include href %URI; #REQUIRED>
<!ELEMENT xsl:strip-space EMPTY>
<!ATTLIST xsl:strip-space elements CDATA #REQUIRED>
<!ELEMENT xsl:preserve-space EMPTY>
<!ATTLIST xsl:preserve-space elements CDATA #REQUIRED>
<!ELEMENT xsl:output EMPTY>
<!ATTLIST xsl:output
method %qname; #IMPLIED
version NMTOKEN #IMPLIED
encoding CDATA #IMPLIED
omit-xml-declaration (yes|no) #IMPLIED
standalone (yes|no) #IMPLIED
doctype-public CDATA #IMPLIED
doctype-system CDATA #IMPLIED
cdata-section-elements %qnames; #IMPLIED
indent (yes|no) #IMPLIED
media-type CDATA #IMPLIED
>
<!ELEMENT xsl:key EMPTY>
<!ATTLIST xsl:key
name %qname; #REQUIRED
match %pattern; #REQUIRED
use %expr; #REQUIRED
>
<!ELEMENT xsl:decimal-format EMPTY>
<!ATTLIST xsl:decimal-format
name %qname; #IMPLIED
decimal-separator %char; "."
grouping-separator %char; ","
infinity CDATA "Infinity"
minus-sign %char; "-"
NaN CDATA "NaN"
percent %char; "%"
per-mille %char; "‰"
zero-digit %char; "0"
digit %char; "#"
pattern-separator %char; ";"
>
<!ELEMENT xsl:namespace-alias EMPTY>
<!ATTLIST xsl:namespace-alias
stylesheet-prefix CDATA #REQUIRED
result-prefix CDATA #REQUIRED
>
<!ELEMENT xsl:template
(#PCDATA
%instructions;
%result-elements;
| xsl:param)*
>
<!ATTLIST xsl:template
match %pattern; #IMPLIED
name %qname; #IMPLIED
priority %priority; #IMPLIED
mode %qname; #IMPLIED
%space-att;
>
<!ELEMENT xsl:value-of EMPTY>
<!ATTLIST xsl:value-of
select %expr; #REQUIRED
disable-output-escaping (yes|no) "no"
>
<!ELEMENT xsl:copy-of EMPTY>
<!ATTLIST xsl:copy-of select %expr; #REQUIRED>
<!ELEMENT xsl:number EMPTY>
<!ATTLIST xsl:number
level (single|multiple|any) "single"
count %pattern; #IMPLIED
from %pattern; #IMPLIED
value %expr; #IMPLIED
format %avt; '1'
lang %avt; #IMPLIED
letter-value %avt; #IMPLIED
grouping-separator %avt; #IMPLIED
grouping-size %avt; #IMPLIED
>
<!ELEMENT xsl:apply-templates (xsl:sort|xsl:with-param)*>
<!ATTLIST xsl:apply-templates
select %expr; "node()"
mode %qname; #IMPLIED
>
<!ELEMENT xsl:apply-imports EMPTY>
<!-- xsl:sort cannot occur after any other elements or
any non-whitespace character -->
<!ELEMENT xsl:for-each
(#PCDATA
%instructions;
%result-elements;
| xsl:sort)*
>
<!ATTLIST xsl:for-each
select %expr; #REQUIRED
%space-att;
>
<!ELEMENT xsl:sort EMPTY>
<!ATTLIST xsl:sort
select %expr; "."
lang %avt; #IMPLIED
data-type %avt; "text"
order %avt; "ascending"
case-order %avt; #IMPLIED
>
<!ELEMENT xsl:if %template;>
<!ATTLIST xsl:if
test %expr; #REQUIRED
%space-att;
>
<!ELEMENT xsl:choose (xsl:when+, xsl:otherwise?)>
<!ATTLIST xsl:choose %space-att;>
<!ELEMENT xsl:when %template;>
<!ATTLIST xsl:when
test %expr; #REQUIRED
%space-att;
>
<!ELEMENT xsl:otherwise %template;>
<!ATTLIST xsl:otherwise %space-att;>
<!ELEMENT xsl:attribute-set (xsl:attribute)*>
<!ATTLIST xsl:attribute-set
name %qname; #REQUIRED
use-attribute-sets %qnames; #IMPLIED
>
<!ELEMENT xsl:call-template (xsl:with-param)*>
<!ATTLIST xsl:call-template
name %qname; #REQUIRED
>
<!ELEMENT xsl:with-param %template;>
<!ATTLIST xsl:with-param
name %qname; #REQUIRED
select %expr; #IMPLIED
>
<!ELEMENT xsl:variable %template;>
<!ATTLIST xsl:variable
name %qname; #REQUIRED
select %expr; #IMPLIED
>
<!ELEMENT xsl:param %template;>
<!ATTLIST xsl:param
name %qname; #REQUIRED
select %expr; #IMPLIED
>
<!ELEMENT xsl:text (#PCDATA)>
<!ATTLIST xsl:text
disable-output-escaping (yes|no) "no"
>
<!ELEMENT xsl:processing-instruction %char-template;>
<!ATTLIST xsl:processing-instruction
name %avt; #REQUIRED
%space-att;
>
<!ELEMENT xsl:element %template;>
<!ATTLIST xsl:element
name %avt; #REQUIRED
namespace %avt; #IMPLIED
use-attribute-sets %qnames; #IMPLIED
%space-att;
>
<!ELEMENT xsl:attribute %char-template;>
<!ATTLIST xsl:attribute
name %avt; #REQUIRED
namespace %avt; #IMPLIED
%space-att;
>
<!ELEMENT xsl:comment %char-template;>
<!ATTLIST xsl:comment %space-att;>
<!ELEMENT xsl:copy %template;>
<!ATTLIST xsl:copy
%space-att;
use-attribute-sets %qnames; #IMPLIED
>
<!ELEMENT xsl:message %template;>
<!ATTLIST xsl:message
%space-att;
terminate (yes|no) "no"
>
<!ELEMENT xsl:fallback %template;>
<!ATTLIST xsl:fallback %space-att;>
D Examples (Non-Normative)
D.1 Document Example
This example is a stylesheet for transforming documents that conform
to a
simple DTD into XHTML [XHTML]. The DTD is:
<!ELEMENT doc (title, chapter*)>
<!ELEMENT chapter (title, (para|note)*, section*)>
<!ELEMENT section (title, (para|note)*)>
<!ELEMENT title (#PCDATA|emph)*>
<!ELEMENT para (#PCDATA|emph)*>
<!ELEMENT note (#PCDATA|emph)*>
<!ELEMENT emph (#PCDATA|emph)*>
The stylesheet is:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/TR/xhtml1/strict">
<xsl:strip-space elements="doc chapter section"/>
<xsl:output
method="xml"
indent="yes"
encoding="iso-8859-1"
/>
<xsl:template match="doc">
<html>
<head>
<title>
<xsl:value-of select="title"/>
</title>
</head>
<body>
<xsl:apply-templates/>
</body>
</html>
</xsl:template>
<xsl:template match="doc/title">
<h1>
<xsl:apply-templates/>
</h1>
</xsl:template>
<xsl:template match="chapter/title">
<h2>
<xsl:apply-templates/>
</h2>
</xsl:template>
<xsl:template match="section/title">
<h3>
<xsl:apply-templates/>
</h3>
</xsl:template>
<xsl:template match="para">
<p>
<xsl:apply-templates/>
</p>
</xsl:template>
<xsl:template match="note">
<p class="note">
<b>NOTE: </b>
<xsl:apply-templates/>
</p>
</xsl:template>
<xsl:template match="emph">
<em>
<xsl:apply-templates/>
</em>
</xsl:template>
</xsl:stylesheet>
With the following input document
<!DOCTYPE doc SYSTEM "doc.dtd">
<doc>
<title>Document Title</title>
<chapter>
<title>Chapter Title</title>
<section>
<title>Section Title</title>
<para>This is a test.</para>
<note>This is a note.</note>
</section>
<section>
<title>Another Section Title</title>
<para>This is <emph>another</emph> test.</para>
<note>This is another note.</note>
</section>
</chapter>
</doc>
it would produce the following result
<?xml version="1.0" encoding="iso-8859-1"?>
<html xmlns="http://www.w3.org/TR/xhtml1/strict">
<head>
<title>Document Title</title>
</head>
<body>
<h1>Document Title</h1>
<h2>Chapter Title</h2>
<h3>Section Title</h3>
<p>This is a test.</p>
<p class="note">
<b>NOTE: </b>This is a note.</p>
<h3>Another Section Title</h3>
<p>This is <em>another</em> test.</p>
<p class="note">
<b>NOTE: </b>This is another note.</p>
</body>
</html>
D.2 Data Example
This is an example of transforming some data represented in XML using
three different XSLT stylesheets to produce three different
representations
of the data, HTML, SVG and VRML.
The input data is:
<sales>
<division id="North">
<revenue>10</revenue>
<growth>9</growth>
<bonus>7</bonus>
</division>
<division id="South">
<revenue>4</revenue>
<growth>3</growth>
<bonus>4</bonus>
</division>
<division id="West">
<revenue>6</revenue>
<growth>-1.5</growth>
<bonus>2</bonus>
</division>
</sales>
The following stylesheet, which uses the simplified syntax described
in [2.3 Literal Result Element
as
Stylesheet], transforms the data into HTML:
<html xsl:version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
lang="en">
<head>
<title>Sales Results By Division</title>
</head>
<body>
<table border="1">
<tr>
<th>Division</th>
<th>Revenue</th>
<th>Growth</th>
<th>Bonus</th>
</tr>
<xsl:for-each select="sales/division">
<!-- order the result by revenue -->
<xsl:sort select="revenue"
data-type="number"
order="descending"/>
<tr>
<td>
<em><xsl:value-of select="@id"/></em>
</td>
<td>
<xsl:value-of select="revenue"/>
</td>
<td>
<!-- highlight negative growth in red -->
<xsl:if test="growth < 0">
<xsl:attribute name="style">
<xsl:text>color:red</xsl:text>
</xsl:attribute>
</xsl:if>
<xsl:value-of select="growth"/>
</td>
<td>
<xsl:value-of select="bonus"/>
</td>
</tr>
</xsl:for-each>
</table>
</body>
</html>
The HTML output is:
<html lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
<title>Sales Results By Division</title>
</head>
<body>
<table border="1">
<tr>
<th>Division</th><th>Revenue</th><th>Growth</th><th>Bonus</th>
</tr>
<tr>
<td><em>North</em></td><td>10</td><td>9</td><td>7</td>
</tr>
<tr>
<td><em>West</em></td><td>6</td><td style="color:red">-1.5</td><td>2</td>
</tr>
<tr>
<td><em>South</em></td><td>4</td><td>3</td><td>4</td>
</tr>
</table>
</body>
</html>
The following stylesheet transforms the data into SVG:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/Graphics/SVG/SVG-19990812.dtd">
<xsl:output method="xml" indent="yes" media-type="image/svg"/>
<xsl:template match="/">
<svg width = "3in" height="3in">
<g style = "stroke: #000000">
<!-- draw the axes -->
<line x1="0" x2="150" y1="150" y2="150"/>
<line x1="0" x2="0" y1="0" y2="150"/>
<text x="0" y="10">Revenue</text>
<text x="150" y="165">Division</text>
<xsl:for-each select="sales/division">
<!-- define some useful variables -->
<!-- the bar's x position -->
<xsl:variable name="pos"
select="(position()*40)-30"/>
<!-- the bar's height -->
<xsl:variable name="height"
select="revenue*10"/>
<!-- the rectangle -->
<rect x="{$pos}" y="{150-$height}"
width="20" height="{$height}"/>
<!-- the text label -->
<text x="{$pos}" y="165">
<xsl:value-of select="@id"/>
</text>
<!-- the bar value -->
<text x="{$pos}" y="{145-$height}">
<xsl:value-of select="revenue"/>
</text>
</xsl:for-each>
</g>
</svg>
</xsl:template>
</xsl:stylesheet>
The SVG output is:
<svg width="3in" height="3in"
xmlns="http://www.w3.org/Graphics/SVG/svg-19990412.dtd">
<g style="stroke: #000000">
<line x1="0" x2="150" y1="150" y2="150"/>
<line x1="0" x2="0" y1="0" y2="150"/>
<text x="0" y="10">Revenue</text>
<text x="150" y="165">Division</text>
<rect x="10" y="50" width="20" height="100"/>
<text x="10" y="165">North</text>
<text x="10" y="45">10</text>
<rect x="50" y="110" width="20" height="40"/>
<text x="50" y="165">South</text>
<text x="50" y="105">4</text>
<rect x="90" y="90" width="20" height="60"/>
<text x="90" y="165">West</text>
<text x="90" y="85">6</text>
</g>
</svg>
The following stylesheet transforms the data into VRML:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<!-- generate text output as mime type model/vrml, using default charset -->
<xsl:output method="text" encoding="UTF-8" media-type="model/vrml"/>
<xsl:template match="/">#VRML V2.0 utf8
# externproto definition of a single bar element
EXTERNPROTO bar [
field SFInt32 x
field SFInt32 y
field SFInt32 z
field SFString name
]
"http://www.vrml.org/WorkingGroups/dbwork/barProto.wrl"
# inline containing the graph axes
Inline {
url "http://www.vrml.org/WorkingGroups/dbwork/barAxes.wrl"
}
<xsl:for-each select="sales/division">
bar {
x <xsl:value-of select="revenue"/>
y <xsl:value-of select="growth"/>
z <xsl:value-of select="bonus"/>
name "<xsl:value-of select="@id"/>"
}
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
The VRML output is:
#VRML V2.0 utf8
# externproto definition of a single bar element
EXTERNPROTO bar [
field SFInt32 x
field SFInt32 y
field SFInt32 z
field SFString name
]
"http://www.vrml.org/WorkingGroups/dbwork/barProto.wrl"
# inline containing the graph axes
Inline {
url "http://www.vrml.org/WorkingGroups/dbwork/barAxes.wrl"
}
bar {
x 10
y 9
z 7
name "North"
}
bar {
x 4
y 3
z 4
name "South"
}
bar {
x 6
y -1.5
z 2
name "West"
}
E Acknowledgements
(Non-Normative)
The following have contributed to authoring this draft:
- Daniel Lipkin, Saba
- Jonathan Marsh, Microsoft
- Henry Thompson, University of Edinburgh
- Norman Walsh, Arbortext
- Steve Zilles, Adobe
This specification was developed and approved for publication by the
W3C
XSL Working Group (WG). WG approval of this specification does not
necessarily imply that all WG members voted for its approval. The
current
members of the XSL WG are:
Sharon Adler, IBM (Co-Chair); Anders Berglund, IBM; Perin Blanchard,
Novell;
Scott Boag, Lotus; Larry Cable, Sun; Jeff Caruso, Bitstream; James
Clark;
Peter Danielsen, Bell Labs; Don Day, IBM; Stephen Deach, Adobe; Dwayne
Dicks,
SoftQuad; Andrew Greene, Bitstream; Paul Grosso, Arbortext; Eduardo
Gutentag,
Sun; Juliane Harbarth, Software AG; Mickey Kimchi, Enigma; Chris Lilley,
W3C;
Chris Maden, Exemplary Technologies; Jonathan Marsh, Microsoft; Alex
Milowski, Lexica; Steve Muench, Oracle; Scott Parnell, Xerox; Vincent
Quint,
W3C; Dan Rapp, Novell; Gregg Reynolds, Datalogics; Jonathan Robie,
Software
AG; Mark Scardina, Oracle; Henry Thompson, University of Edinburgh;
Philip
Wadler, Bell Labs; Norman Walsh, Arbortext; Sanjiva Weerawarana, IBM;
Steve
Zilles, Adobe (Co-Chair)
F Changes
from
Proposed Recommendation (Non-Normative)
The following are the changes since the Proposed Recommendation:
G
Features under Consideration for Future Versions of XSLT (Non-Normative)
The following features are under consideration for versions of XSLT
after
XSLT 1.0:
a conditional expression;
support for XML Schema datatypes and archetypes;
support for something like style rules in the original XSL
submission;
an attribute to control the default namespace for names
occurring in
XSLT attributes;
support for entity references;
support for DTDs in the data model;
support for notations in the data model;
a way to get back from an element to the elements that
reference it
(e.g. by IDREF attributes);
an easier way to get an ID or key in another document;
support for regular expressions for matching against any or all
of
text nodes, attribute values, attribute names, element type names;
case-insensitive comparisons;
normalization of strings before comparison, for example for
compatibility characters;
a function string resolve(node-set) function that
treats the value of the argument as a relative URI and turns it into
an
absolute URI using the base URI of the node;
multiple result documents;
defaulting the select attribute on
xsl:value-of to the current node;
an attribute on xsl:attribute to control how the
attribute value is normalized;
additional attributes on xsl:sort to provide
further
control over sorting, such as relative order of scripts;
a way to put the text of a resource identified by a URI into
the
result tree;
allow unions in steps (e.g. foo/(bar|baz));
allow for result tree fragments all operations that are allowed
for
node-sets;
a way to group together consecutive nodes having duplicate
subelements or attributes;
features to make handling of the HTML style
attribute
more convenient.
