INPUT

<pop>
<feature><f>featureid1</f><p>pubid1</p></feature>
<feature><f>featureid1</f><p>pubid2</p></feature>
<feature><f>featureid2</f><p>pubid1</p></feature>
<feature><f>featureid3</f><p>pubid1</p></feature>
<feature><f>featureid3</f><p>pubid2</p></feature>
</pop>

STYLESHEET

<xsl:stylesheet version="2.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 
 <xsl:output indent="yes"/>
 
 <xsl:template match="pop">
  <xsl:variable name="v">
   <xsl:for-each-group select="feature" group-by="f">
   <feature>
    <f><xsl:value-of select="current-grouping-key()" /></f>
    <p>
      <xsl:value-of separator=", ">
        <xsl:perform-sort select="current-group()/p">
          <xsl:sort select="."/>
        </xsl:perform-sort>
      </xsl:value-of>
    </p>
   </feature> 
   </xsl:for-each-group>
  </xsl:variable>
   <xsl:for-each-group select="$v/feature" group-by="p">
   <feature>
    <f><xsl:value-of select="current-group()/f" separator=", "/></f>
    <p><xsl:value-of select="current-grouping-key()" /></p>
   </feature> 
   </xsl:for-each-group>
</xsl:template>

</xsl:stylesheet>

OUTPUT

<?xml version="1.0" encoding="UTF-8"?>
<feature>
   <f>featureid1, featureid3</f>
   <p>pubid1, pubid2</p>
</feature>
<feature>
   <f>featureid2</f>
   <p>pubid1</p>
</feature>

Michael Kay
http://www.saxonica.com/

 

> -----Original Message-----
> From: Josh Goodman [mailto:jogoodma@xxxxxxxxxxx] 
> Sent: 07 September 2006 16:04
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  Complicated grouping question
> 
> Hi all,
> 
> I have a XSL grouping problem that I am having difficulty 
> with and for which I couldn't find a previous post about in 
> the archives.  I also noticed that there hadn't been a 
> grouping question in a day or so I thought I would do my part 
> to help out :-).
> 
> I'm using XSLT 2.0 as implemented by Saxon 8.8 (congrats to 
> Michael on this latest version).  The XML I'm working with 
> looks like this:
> 
> <feature>
>    <id>BACR48K23</id>
>    <pub>
>       <id>0105495</id>
>    </pub>
> </feature>
> ...
> 
> This can sometimes be repeated over again with a new 
> feature/id and the same pub/id, a new pub/id and the same 
> feature/id, or both ids being completely new.
>  Each feature chunk is adjacent to the others but they are in 
> random order.  A completely flat view of this would look like 
> this for example
> 
> featureid1     pubid1
> featureid1     pubid2
> featureid2     pubid1
> featureid3     pubid1
> featureid3     pubid2
> 
> The grouping I would like to do is first group by featureid 
> to produce this list.
> 
> featureid1     pubid1, pubid2
> featureid2     pubid1
> featureid3     pubid1, pubid2
> 
> This is no problem using something along the lines of
> 
> <xsl:for-each-group select="feature" group-by="id">
>     <xsl:value-of select="current-grouping-key()" />
>     <xsl:value-of select="current-group()/pub/id" 
> separator=", " /> </xsl:for-each-group>
> 
> The problem comes in to play because I need to do another 
> round of grouping.
> This time on items from the second list grouped by those with 
> a common set of pubid's.  Doing this on the above list would 
> produce this:
> 
> featureid1, featureid3     pubid1, pubid2
> featureid2                 pubid1
> 
> I've not been able to wrap my head around the best way to 
> achieve this.  Anyone have suggestions?
> 
> Thanks,
> Josh Goodman