RE: [xsl] Number of elements with a given attribute

["Michael Kay" <mike@xxxxxxxxxxxx>]

> In a piece of theater, I have some verses that are split
> between different roles.
>
> The other are tagged on the following model:
> <role name='...'>
>    ...
>   <verse>...</verse>
>   <verse part="beginning">...</verse>
> </role>
> <role name='...'>
>   <verse part="continuation">...</verse> </role> <role name='...'>
>   <verse part="continuation">...</verse> </role> <role name='...'>
>   <verse part="end">...</verse>
>   <verse>...</verse>
>   ...
> </role>
>

> I wish to have the count of preceding parts of verse from the
> last beginning part.
> Regards,

A classic case of two overlapping hierarchies running over the same data.
One of these hierarchies is represented directly in the XML tree structure,
the other is represented indirectly. You want to perform an operation on the
"hidden" hierarchy, so it's best to invert the structure so the verse
hierarchy becomes the primary one. That is, you want:

<verse>
  <part role="a">...</part>
  <part role="a">...</part>
  <part role="b">...</part>
</verse>
<verse>
   ...

which can be done like this:

<xsl:for-each-group select="$verses"
group-starting-with="verse[empty(@part)] | verse[@part='beginning']">
  <xsl:variable name="verse-number" select="position()"/>
  <verse>
    <xsl:for-each select="current-group()">
      <part role="parent::role/@name">
        <xsl:copy-of select="node()"/>
      </part>
    </xsl:for-each>
  </verse>
</xsl:for-each-group>

You now have each verse represented by a complete element, broken into parts
to show who speaks each part of the verse, and this makes it easy for
example to number the parts of a verse as you have asked for.

Regards,

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