trouble with xsl:for-each selection using xsl:variable
Problem:
I am having trouble generating an xpath expression that selects a node in a different section of the XML document by position. I am using xsl:variable to create the expression, but when I use a xsl:for-each with the value of the xsl:variable as my select statement I get an error.
<xsl:variable name="input_params_query">
<xsl:text disable-output-escaping="yes">/example/inputs/dataset[</xsl:text>
<xsl:number value="position()" format="1" />
<xsl:text disable-output-escaping="yes">]/parameter</xsl:text>
</xsl:variable>
<xsl:for-each select="$input_params_query">
<input rdf:resource="#{@name}"/>
</xsl:for-each>
Results in the error:
The 'select' expression does not evaluate to a node set.
When I print out the value of the xsl:variable I am using I get:
/example/inputs/dataset[1]/parameter
which is a valid and correct Xpath expression for the nodes I am trying to select in the for-each call.
Is my usage of the xsl:variable as xsl:for-each select attribute incorrect?
Background and Full Explanation:
I am using XSLT to generate a RDF/XML representation of information available in the following XML structure.
In this case what the XML really means is that a process was run twice; the first time generating output file "a" and the second time generation output file "b". The parameters "p1" and "p2" were inputs for the executi开发者_StackOverflowon that generated file "a" and the parameter "p3" was an input to the execution that generated file "b".
For each output of 'process' I am generating a RDF individual and defining the inputs and outputs for that process execution. Basically, I want to define all values from /example/inputs/dataset[n]/parameters as inputs to the process which generates the output /example/process/outputs/file[n].
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
version="1.0">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:template match="//process">
<xsl:for-each select="outputs/*">
<!-- declare rdf resource of type Process, define Process outputs -->
<!-- ... this I already have working so I have withheld for brevity -->
<!-- define input parameters -->
<xsl:variable name="input_params_query">
<xsl:text disable-output-escaping="yes">/example/inputs/dataset[</xsl:text>
<xsl:number value="position()" format="1" />
<xsl:text disable-output-escaping="yes">]/parameter</xsl:text>
</xsl:variable>
<xsl:for-each select="$input_params_query">
<input rdf:resource="#{@name}"/>
</xsl:for-each>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
"Is my usage of the xsl:variable as xsl:for-each select attribute incorrect?"
yes. the value specified in select attributes must be a valide node-set expression, that is, it must be an Xpath expression that evaluates to a (possibly empty) node set.
The variable you defined is of a string type. the string happens to be a valid Xpath expression, but it is still 'just' a string.
I think you can achieve your intended result by writing it like this:
<xsl:template match="//process">
<xsl:for-each select="outputs/*">
<!-- declare rdf resource of type Process, define Process outputs -->
<!-- ... this I already have working so I have withheld for brevity -->
<!-- define input parameters -->
<xsl:variable name="position" select="position()"/>
<xsl:for-each select="/example/inputs/dataset[$position]">
<input rdf:resource="#{@name}"/>
</xsl:for-each>
</xsl:for-each>
</xsl:template>
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