Recipe 6.11. Understanding the New Capabilities of Old XSLT 1.0 Features Problem There are numerous little enhancements in XSLT 2.0, and it is difficult to get a quick handle on all of them. Solution Many of the capabilities in 2.0 are delivered as enhancements to existing 1.0 instructions and functions. These are not as obvious as those that are packaged as completely new instructions or functions. This section provides a one-stop overview of these enhancements. xsl:apply-templates The mode attribute can take the value #current to signify that the processing should continue with the current mode. You can take advantage of support for sequences by writing a comma-separated list (e.g., <xsl:apply-templates select="title, heading, para"/> ) when you want to process title elements first, then heading elements, and then para elements. In 1.0, you had to write three separate apply-template instructions.  | In both 1.0 and 2.0, you can write: <xsl:apply-templates select="title | heading | para"/>
but this is an unordered application. The child nodes will be processed as they appear in the document and not as you order them in the select. |
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xsl:attribute A big pet peeve of many XSLT 1.0 developers was the inability to write <xsl:attribute name="foo" select="10"/> since the select attribute was not supported. Now it is supported, and you should prefer it when defining simple attributes, although the sequence constructor syntax is still available. The attributes type and validation were added in support of schema-aware processors. Type is used to specify native or user-defined types defined by W3C schema. Validation is used to specify how the attribute should be validated.
xsl:call-template The result of the call can be an arbitrary sequence (such as a sequence of integers) rather than just a node set. You will get an error if you supply a parameter (via xsl:with-param) that the called template does not define.
xsl:comment xsl:copy and xsl:copy-of A new attribute, copy-namespaces="yes | no", is available to specify whether the namespace nodes of an element should be copied. The default is yes, which is consistent with 1.0 behavior. The attribute type was added to specify native or user-defined types defined by W3C Schema. The attribute validation was added to specify how the result should be validated or whether existing type annotations should be preserved.
xsl:element xsl:for-each Can now process arbitrary sequences in addition to sequences of nodes: <xsl:for-each select="(1, 2, 3, 4, 5)"> <xsl:value-of select="."/><xsl:text>)
</xsl:text> </xsl:for-each>
xsl:key The match and use attributes can now refer to global variables, provided there is no circularity between the value of the variables and the key: <xsl:variable name="state" select=" 'active' "/> <xsl:key name="state-key" match="employee[@state=$state]" use="@type"/>
The use attribute can be replaced by the value of a sequence constructor: <!--defining the value of a key using some sophisticated processing --> <xsl:key name="sick-key" select="employee"> <xsl:apply-templates select="record[@type='sick-day']" mode="sick-key"/> </xsl:key>
xsl:message The terminate attribute can now be an attribute value template. This greatly simplifies global changes to the termination behavior. A select attribute is now supported in addition to the sequence constructor form: <xsl:param name="terminate" select=" 'no' "/> <xsl:template match="employee"> <xsl:if test="not(@type)"> <xsl:message terminate="{$terminate}" select=" 'Missing type attribute for employee' "/> <xsl:if> </xsl:template>
xsl:number A select attribute has been added to allow nodes other than the context node to be numbered. Formatting options have been enhanced to allow output as a word such as "one", "two", "three" according to the chosen language: <-- This outputs 'Ten' --> <xsl:number value="10" format="Ww"/> <-- This outputs 'ten' --> <xsl:number value="10" format="w"/> <-- This outputs 'TEN' --> <xsl:number value="10" format="W"/>
xsl:output Can be given a name so that it can be used with the new xsl:result-document instruction. See Recipe 6.10 for details. A new method, XHTML, is supported. A new attribute, escape-uri-attributes, determines whether URI attributes in HTML and XHTML output should be escaped. A new attribute, include-content-type, determines if a <meta> element should be added to the output to indicate the content type and encoding. A new attribute, normalize-unicode, determines if Unicode characters should be normalized. See http://www.w3.org/TR/2002/WD-charmod-20020430/ for further details on normalization. A new attribute, undeclare-namespaces, determines if namespaces in XML 1.1 should be undeclared when they go out of scope. A namespace is undeclared by xmlns:pre="", where pre is some prefix. A new attribute, use-character-maps, allows you to provide a list of names of character maps. See Recipe 6.8.
xsl:param An as attribute can be used to specify the type of the parameter. A required attribute can be used to specify whether the parameter is mandatory or optional. A tunnel attribute is used to indicate whether tunneling is supported for this parameter. See Recipe 6.6.
xsl:processing-instruction xsl:strip-space xsl:stylesheet A new default-validation attribute determines the default validation to use when new element and attribute nodes are created and the instruction that creates them lacks a validation attribute. A new xpath-default-namespace attribute determines the namespace used for unprefixed element names in XPath expressions.
xsl:template Multiple modes are supported via #all or list of modes in the mode attribute. An as attribute allows the result type to be specified. The match attribute supports matching on types. The match attribute can reference global variables or parameters.
xsl:value-of xsl:variable xsl:with-param An as attribute can be used to specify the type of the parameter. A tunnel attribute is used to indicate whether tunneling is supported for this parameter. See Recipe 6.6. Can now be used with xsl:apply-imports and the new xsl:next-match instruction. See Recipe 6.6.
current( ) The function can return generalized items (such as a string) in addition to nodes. Can now be used within a match pattern to refer to the element that matched. <!-- Match nodes with descendant elements that have an attributes whose value matches the local name matched element --> <xsl:template match="*[descendant::*/@* = local-name(current( ))]">
document( ) function-available( ) key( ) system-property( ) An xsl:product property is defined to return the name of the XSLT processor (e.g., Saxon). An xsl:product-version property is defined to return the version of the XSLT processor (e.g., 8.1). An xsl:is-schema-aware property is defined to return yes or no to indicate if the processor is schema aware. An xsl:supports-serialization property is defined to return yes or no to indicate if the processor supports serialization. An xsl:supports-backwards-compatibility property is defined to return yes or no to indicate if the processor supports backward-compatibility mode (e.g., version="1.0").
Discussion The main themes that govern the new capabilities of old XSLT instructions are type support and consistency. Here consistency largely means support for a select attribute when only a sequence constructor was supported in the past or visa versa. | One quirk of the XSLT creators is that they continue to introduce two distinct names for constructs where, to my way of thinking, one would have sufficed. In particular, consider the attributes as and type. They are never used together, so why not just type? A similar argument could have been made for eliminating xsl:with-param in favor of just xsl:param when 1.0 was specified. |
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