[xsl] Kosher XSLT 3.0 numbering solution?

["David Sewell dsewell@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

I have a numbering task that is trivially easy to handle using an XSLT extension 
that permits modification of global variables (such as saxon:assign) but which 
is harder to accomplish via pure XSLT. I don't *need* to accomplish this as I 
have code that works fine, but I'm just curious about alternate solutions.

I have an XML file representing the contents of a printed book. I need to add 
page break indicators that carry the page numeration, e.g. <pb n="51"/>. Because 
I'm lazy, I just want to plug in empty  markers and then run a script to add the 
numeration.

This would be a straightforward job for xsl:number if all pagination was 
sequential. However, parts of the book are commented out, so there may be a page 
jump from say page 11 to page 30. In a case like that, I will insert <pb 
n="30"/> to provide a hard-coded indication of the number. That makes use of 
xsl:number more complicated. The solution via updates to a global variable is 
simple, along the lines of

  <xsl:variable name="bodyPageNo" select="0" as="xs:integer" saxon:assignable="yes"/>
  <xsl:template match="pb">
    <xsl:variable name="pageNumber">
       <saxon:assign name="bodyPageNo" select="
          if (@n) then xs:integer(@n) else $bodyPageNo + 1
          "/>
       <xsl:value-of select="$bodyPageNo"/>
    </xsl:variable>
   [etc.]

If I avoid saxon:assign, I don't see any way around some moderately messy 
brute-force calculation in the <pb> template to identify the closest preceding 
<pb> element with an @n value (if any), and use that value plus the number of 
intervening <pb> elements to assign a numeration to the current element. Does 
anything jump out as a more elegant approach?

David


--
David Sewell
Manager of Digital Initiatives
The University of Virginia Press
Email: dsewell@xxxxxxxxxxxx   Tel: +1 434 924 9973
Web: http://www.upress.virginia.edu/rotunda