Here's a quick and dirty method to convert your flat sample to nested
hierarchy. I didn't copy all the supposed markup here, just created
the hierarchy. My source file was:

<?xml version='1.0' encoding='utf-8'?>
<text>
   <flat lvl="1"> {markupA} </flat>
   <flat lvl="2"> {markupB} </flat>
   <flat lvl="2"> {markupC} </flat>
   <flat lvl="1"> {markupD} </flat>
   <flat lvl="2"> {markupE} </flat>
   <flat lvl="2"> {markupF} </flat>
   <flat lvl="3"> {markupG} </flat>
   <flat lvl="4"> {markupH} </flat>
   <flat lvl="4"> {markupI} </flat>
   <flat lvl="3"> {markupJ} </flat>
   <flat lvl="3"> {markupK} </flat>
   <flat lvl="2"> {markupL} </flat>
   <flat lvl="1"> {markupM} </flat>
</text>

<?xml version='1.0' encoding='utf-8'?>
<xsl:stylesheet version='1.0' xmlns:xsl='http://www.w3.org/1999/XSL/
Transform'>

<xsl:template match="/">
  <xsl:call-template name="nest">
    <xsl:with-param name="flat" select="text/flat[1]" />
  </xsl:call-template>
</xsl:template>

<xsl:template name="nest">
  <xsl:param name="flat" />
  <xsl:element name="nest">
    <xsl:value-of select="$flat" />
    <xsl:if test="$flat/following::flat[1]/@lvl &gt; $flat/@lvl">
      <xsl:call-template name="nest">
        <xsl:with-param name="flat" select="$flat/following::flat
[1]" />
      </xsl:call-template>
    </xsl:if>
  </xsl:element>
  <xsl:variable name="next" select="$flat/following::flat[@lvl &lt;=
$flat/@lvl]" />
  <xsl:if test="$next[1]/@lvl = $flat/@lvl">
    <xsl:call-template name="nest">
      <xsl:with-param name="flat" select="$next[1]" />
    </xsl:call-template>
  </xsl:if>
</xsl:template>

Kind regards,
--
Mikhail Edoshin
m.edoshin@xxxxxxx

Michael Kay wrote:

You'll find a paper that tackles this problem (using XSLT 2.0) at

http://www.idealliance.org/proceedings/xml04/papers/111/mhk-
paper.html

The reverse transformation is much easier: you just process all the
elements in document order (//nest) and for each one compute its
level number as count(ancestor::*).

Thank you for your prompt answer.

Since I am a newbie at this, it'll take me a while to understand your
paper (and XSLT in general.) But I assume from your reply that the
transformation from 'flat' to 'nested' (which is of most interest to
me at the moment) is doable with XSLT 2.0.

Of course, would love to see an XSLT 2.0 transformation specific to
the 'flat' to 'nested' example, if someone here has the interest --
and a moment to spare. That will greatly help. It also seems "generic"
enough that the transformation may be useful to someone else in the
future.

Again, much thanks.

Mark
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  Watch-O-Matic
  watchomatic@xxxxxxxxxxx

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