Question

I have an XML document structured as follows

<items>
 <item>
  <name>item1</name>
  <attributes>a,b,c,d</attributes>
 </item>
 <item>
  <name>item2</name>
  <attributes>c,d,e</attributes>
 </item>
</items>

For each unique attribute value (delimited by commas) I need to list all item names associated with that value like so:

a : item1
b : item1
c : item1, item2
d : item1, item2
e : item2

My initial plan was to use a template to parse the attributes into Attribute nodes, surrounding each with appropriate tags, and then separating out the unique values with an XPATH expression like

Attribute[not(.=following::Attribute)]

but since the result of the template isn’t a node-set that ever goes through an XML parser, I can’t traverse it. I also tried exslt’s node-set() function only to realize it does not allow me to traverse the individual Attribute nodes either.

At this point I’m at a loss for a simple way to do this and would really appreciate any help or ideas on how to proceed. Thanks!

Answer 1

This transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:msxsl="urn:schemas-microsoft-com:xslt"
 xmlns:ext="http://exslt.org/common">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:key name="kAtrByVal" match="attr" use="."/>

 <xsl:template match="/">
  <xsl:variable name="vrtfPass1">
   <groups>
    <xsl:apply-templates/>
   </groups>
  </xsl:variable>

  <xsl:variable name="vPass1"
       select="ext:node-set($vrtfPass1)"/>

  <xsl:apply-templates select="$vPass1/*"/>
 </xsl:template>

 <xsl:template match="item">
  <group name="{name}">
   <xsl:apply-templates select="attributes"/>
  </group>
 </xsl:template>

 <xsl:template match="attributes" name="tokenize">
  <xsl:param name="pText" select="."/>

  <xsl:if test="string-length($pText)">
   <xsl:variable name="vText" select=
        "concat($pText,',')"/>
   <attr>
    <xsl:value-of select="substring-before($vText,',')"/>
   </attr>
   <xsl:call-template name="tokenize">
    <xsl:with-param name="pText" select=
    "substring-after($pText,',')"/>
   </xsl:call-template>
  </xsl:if>
 </xsl:template>

 <xsl:template match=
  "attr[generate-id()
       =
        generate-id(key('kAtrByVal',.)[1])
       ]
  ">
  <xsl:value-of select="concat('&#xA;',.,': ')"/>

  <xsl:for-each select="key('kAtrByVal',.)">
   <xsl:value-of select="../@name"/>
   <xsl:if test="not(position()=last())">
    <xsl:text>, </xsl:text>
   </xsl:if>
  </xsl:for-each>
 </xsl:template>

 <xsl:template match="text()"/>
</xsl:stylesheet>

when applied on the provided XML document:

<items>
    <item>
        <name>item1</name>
        <attributes>a,b,c,d</attributes>
    </item>
    <item>
        <name>item2</name>
        <attributes>c,d,e</attributes>
    </item>
</items>

produces the wanted, correct result:

a: item1
b: item1
c: item1, item2
d: item1, item2
e: item2

Explanation:

1. Pass1: tokenization and end result:

---

<groups>
  <group name="item1">
    <attr>a</attr>
    <attr>b</attr>
    <attr>c</attr>
    <attr>d</attr>
  </group>
  <group name="item2">
    <attr>c</attr>
    <attr>d</attr>
    <attr>e</attr>
  </group>
</groups>

.2. Pass2 takes the result of Pass1 (converted to a nodeset using the extension function ext:node-set()) as input, performs Muenchian grouping and produces the final, wanted result.