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

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

Here is a slightly different solution, developed before I noticed Dimitre's post.
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="yes"/>
<xsl:strip-space elements="*" />
<xsl:key name="kParents" match="*[object_id]" use="local-name()" />
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()" />
</xsl:copy>
</xsl:template>
<xsl:template match="*[*/object_id]">
<xsl:variable name="grandparent-id" select="generate-id()" />
<xsl:copy>
<xsl:apply-templates select="#* | node()[not(object_id)] |
*[generate-id()=
generate-id(
key('kParents',local-name())[generate-id(..)=$grandparent-id][1])]"
mode="group-head" />
</xsl:copy>
</xsl:template>
<xsl:template match="*[object_id]" mode="group-head">
<xsl:variable name="grandparent-id" select="generate-id(..)" />
<xsl:copy>
<xsl:apply-templates select="#* | node()[not(self::object_id)]" />
<xsl:for-each select="key('kParents',local-name())[generate-id(..)=$grandparent-id]/object_id">
<xsl:value-of select="." />
<xsl:if test="position() != last()"> - </xsl:if>
</xsl:for-each>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
Update
I updated the style-sheet to reflect the OP's comment about '-' being a delimiter, rather that a separator between first and last values.

Answer 2

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:
Proper use and overriding of the identity rule.
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>