Question

I have following xml. Note that node n1 and n3 have same children (order can be different). How can I write an XSL transformation to identify such nodes?

<Document>
    <Node name="n1">
        <Item value="v1">
        <Item value="v2">
        <Item value="v3">
    </Node>
    <Node name="n2">
        <Item value="p1">
        <Item value="p2">
        <Item value="p3">
    </Node>
    <Node name="n3">
        <Item value="v3">
        <Item value="v1">
        <Item value="v2">
    </Node>
</Document>

Answer 1

Here is a complete XSLT 1.0 solution that is general enough so that it would produce correct results even when a Node is allowed to have children with any name:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 xmlns:ext="http://exslt.org/common" exclude-result-prefixes="ext">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:key name="kNodeBySign" match="Node" use="@signature"/>

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

     <xsl:apply-templates mode="pass2"
          select="ext:node-set($vrtfPass1)"/>
 </xsl:template>

 <xsl:template match="Node">
  <Node name="{@name}">
   <xsl:variable name="vSignature">
    <xsl:for-each select="*">
     <xsl:sort select="name()"/>
     <xsl:sort select="@value"/>
      <xsl:value-of select="concat(name(),'+++',@value)"/>
    </xsl:for-each>
  </xsl:variable>

  <xsl:attribute name="signature">
   <xsl:value-of select="$vSignature"/>
  </xsl:attribute>
  </Node>
 </xsl:template>

 <xsl:template match="/" mode="pass2">
  <xsl:for-each select=
    "Node[generate-id()
         =
          generate-id(key('kNodeBySign',@signature)[1])
         ]
    ">

    <Node name="{@name}">
      <xsl:variable name="vNodesInGroup">
        <xsl:for-each select=
          "key('kNodeBySign',@signature)[position()>1]">
          <xsl:value-of select="concat(@name, ' ')"/>
        </xsl:for-each>
      </xsl:variable>

      <xsl:attribute name="matches">
       <xsl:value-of select="$vNodesInGroup"/>
      </xsl:attribute>
    </Node>
  </xsl:for-each>
 </xsl:template>
</xsl:stylesheet>

when applied on this XML document:

<Document>
    <Node name="n1">
        <Item value="v1"/>
        <Item value="v2"/>
        <Item value="v3"/>
    </Node>
    <Node name="n2">
        <Item value="p1"/>
        <Item value="p2"/>
        <Item value="p3"/>
    </Node>
    <Node name="n3">
        <Item value="v3"/>
        <Item value="v1"/>
        <Item value="v2"/>
    </Node>
    <Node name="n4">
        <Item value="p3"/>
        <Item value="v1"/>
        <Item value="v2"/>
    </Node>
    <Node name="n5">
        <Item value="v2"/>
        <Item value="v1"/>
        <Item value="v3"/>
    </Node>
    <Node name="n6">
        <Item value="v2"/>
        <Item value="v1"/>
        <Item value="v3"/>
        <Item value="v4"/>
    </Node>
    <Node name="n7">
        <Item value="v1"/>
        <Item value="v1"/>
        <Item value="v2"/>
        <Item value="v3"/>
        <Item value="v4"/>
    </Node>
</Document>

the wanted, correct result is produced:

<Node name="n1" matches="n3 n5 "/>
<Node name="n2" matches=""/>
<Node name="n4" matches=""/>
<Node name="n6" matches=""/>
<Node name="n7" matches=""/>

Explanation:

1. This is a two-pass transformation.

2. The result of the first pass is an XML fragment containing Node elements with their name attribute and one newly added attribute: signature. This is the concatenation of the names and values of all children (in normal, sorted form). The result of pass1 in this concrete case is the following:

3. In pass 2 we use the Muenchian method for grouping all Node elements by their signature attribute. The first Node in every group is represented in the output with a new attribute matches whose value is the space-delimited concatenation of the name attributes of the remaining Node elements in the current group.