Re: best-technique for selective group and merge?

The feature can contain multiple configs,
each of which I want to merge across features:
...
I want to be able to select /config_datastore/site/* and perform selective
grouping (on feature @name) and merging (on the feature/config elements)
to return:
...

T:\ftemp>type jim.xml
<?xml version="1.0"?>
  <config_datastore>
    <feature name="a">
      <config id="1">
        <param id="x">x</param>
      </config>
      <config id="2">
        <param id="xx">xx</param>
      </config>
      <config id="3">
        <param id="xxx">xxx</param>
      </config>
    </feature>
    <feature name="b">
      <config id="1">
        <param id="y">y</param>
      </config>
      <config id="2">
        <param id="yy">yy</param>
      </config>
    </feature>
    <feature name="c">
      <config id="1">
        <param id="z">z</param>
      </config>
      <config id="2">
        <param id="zz">zz</param>
      </config>
    </feature>
    <site>
      <has_feature name="a"/>
      <has_feature name="c"/>
    </site>
  </config_datastore>

T:\ftemp>type jim.xsl
<?xml version="1.0" encoding="iso-8859-1"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                version="1.0">

<xsl:template match="/">
  <result>
    <xsl:variable name="configs"
                  select="/*/feature[@name=/*/site/has_feature/@name]/config"/>
    <xsl:for-each select="$configs">
      <xsl:if test="generate-id(.)=
                    generate-id($configs[@id=current()/@id])">
        <config id="{@id}">
          <xsl:copy-of select="$configs[@id=current()/@id]/*"/>
        </config>
      </xsl:if>
    </xsl:for-each>
  </result>
</xsl:template>

</xsl:stylesheet>
T:\ftemp>saxon jim.xml jim.xsl
<?xml version="1.0" encoding="utf-8"?>
<result>
   <config id="1">
      <param id="x">x</param>
      <param id="z">z</param>
   </config>
   <config id="2">
      <param id="xx">xx</param>
      <param id="zz">zz</param>
   </config>
   <config id="3">
      <param id="xxx">xxx</param>
   </config>
</result>
T:\ftemp>rem Done!

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