XSLT 1.0 - Concatenate known child nodes, group by unknown parent

Question

I want to transform

    <entry>
        <parent1>
            <object_id>1580</object_id>
        </parent1>
        <parent1>
            <object_id>1586</object_id>
        </parent1>
        <parent2>
            <object_id>1582</object_id>
        </parent2>
        <parent2>
            <object_id>1592</object_id>
        </parent2>
    </entry>

into

    <entry>
        <parent1>1580-1586</parent1>
        <parent2>1582-1592</parent2>
    </entry>

Top-level entry name is unknown. Parent names are unknown, and the number of parent nodes with the same name can vary. Child nodes are known "object_id".

So, I would like to group the unknown parents in an abstract way, and concatenate child node values, delimited by "-".

Merge XML nodes using XSLT comes close to answering the question, as does Group/merge childs of same nodes in xml/xslt , but they're not quite what I need.

So far I have:

    <xsl:key name="groupName" match="*[object_id]" use="."/>
    <xsl:template match="*[generate-id(.) = generate-id(key('groupName', .))]">
        <xsl:copy>
        <xsl:call-template name="join"> 
                <xsl:with-param name="list" select="object_id" /> 
                <xsl:with-param name="separator" select="'-'" />                                             
        </xsl:call-template>
        </xsl:copy> 
    </xsl:template>

    <xsl:template name="join"> 
    <xsl:param name="list" /> 
    <xsl:param name="separator"/>     
    <xsl:for-each select="$list"> 
      <xsl:value-of select="." /> 
      <xsl:if test="position() != last()"> 
        <xsl:value-of select="$separator" />         
      </xsl:if> 
    </xsl:for-each> 
    </xsl:template>

Thanks in advance!

Answer 1

This transformation:

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

 <xsl:key name="kObjByValAndParent" match="object_id"
  use="name(..)"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="/*/*"/>

 <xsl:template priority="2" match=
 "/*/*[generate-id(object_id)
      =
       generate-id(key('kObjByValAndParent',name())[1])
      ]
 ">
   <xsl:copy>
     <xsl:value-of select=
     "concat(object_id, ' - ',
             key('kObjByValAndParent',name())[last()]
            )
     "/>
   </xsl:copy>
 </xsl:template>
</xsl:stylesheet>

when applied on the provided XML document:

<entry>
    <parent1>
        <object_id>1580</object_id>
    </parent1>
    <parent1>
        <object_id>1586</object_id>
    </parent1>
    <parent2>
        <object_id>1582</object_id>
    </parent2>
    <parent2>
        <object_id>1592</object_id>
    </parent2>
</entry>

produces the wanted, correct result:

<entry>
   <parent1>1580 - 1586</parent1>
   <parent2>1582 - 1592</parent2>
</entry>

Explanation:

1. Proper use and overriding of the identity rule.

2. Proper use of the Muenchian grouping method.

---

II. In case all values must be concatenated together, use this slightly modified solution:

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

 <xsl:key name="kObjByValAndParent" match="object_id"
  use="name(..)"/>

 <xsl:template match="node()|@*">
  <xsl:copy>
   <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="/*/*"/>

 <xsl:template priority="2" match=
 "/*/*[generate-id(object_id)
      =
       generate-id(key('kObjByValAndParent',name())[1])
      ]
 ">
   <xsl:copy>
     <xsl:for-each select="key('kObjByValAndParent',name())">
      <xsl:if test="not(position()=1)"> - </xsl:if>
      <xsl:value-of select="."/>
     </xsl:for-each>
   </xsl:copy>
 </xsl:template>
</xsl:stylesheet>