Re: [xsl] flatened hiearchies for xslt2

["Dimitre Novatchev" <dnovatchev@xxxxxxxxx>]

> My question is:
> What is the best approach to transform the "flat" structure back to the
> original logical structure, with XSLT2 (Saxon), assuming that only the
> 'flat' version is received by the application?

Something as simple as this transformation (XSLT 1.0):

<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="kChildren" match="section"
   use="generate-id(preceding::section
                         [@level = current()/@level - 1]
                         [last()]
                    )"
 />
	
 <xsl:template match="/">
    <section id="logical">
      <xsl:apply-templates select="*/section[@level = 1]"/>
    </section>
 </xsl:template>
	
	<xsl:template match="section[@level]">
	  <xsl:copy>
	    <xsl:copy-of select="@*"/>
	    <xsl:apply-templates select="key('kChildren', generate-id())"/>
	  </xsl:copy>
	</xsl:template>
</xsl:stylesheet>

When applied on the provided source xml document:

<section id="flat">
	<section id="1" level="1"/>
	<section id="1-1" level="2"/>
	<section id="1-2" level="2"/>
	<section id="1-2-1" level="3"/>
	<section id="1-2-2" level="3"/>
	<section id="2" level="1"/>
</section>

the wanted result is produced:

<section id="logical">
 <section id="1" level="1">
   <section id="1-1" level="2">
     <section id="1-2-1" level="3" />
     <section id="1-2-2" level="3" />
   </section>
   <section id="1-2" level="2" />
 </section>
 <section id="2" level="1" />
</section>

--
Cheers,
Dimitre Novatchev
---------------------------------------
Truly great madness cannot be achieved without significant intelligence.
---------------------------------------
To invent, you need a good imagination and a pile of junk
-------------------------------------
You've achieved success in your field when you don't know whether what
you're doing is work or play


On 3/7/07, ac <ac@xxxxxxxxxxxxx> wrote:
> Hi,
>
> I love functional programming, XSLT2, and Saxon.
>
> I recently faced what first seemed like a simple case, yet it got me
> scratching my head for a while, before figuring a workaround for the
> real-life problem at hand.  Still it seems so simple that there must be
> cleaner way ...
>
> If the following recursive logical XML structure
>      <section id="logical">
>         <section id="1">
>             <section id="1-1"/>
>             <section id="1-2">
>                 <section id="1-2-1"/>
>                 <section id="1-2-2"/>
>             </section>
>         </section>
>         <section id="2">
>         </section>
>     </section>
>
> can easily be transformed to its flattened equivalent, like:
>     <section id="flat">
>         <section id="1" level="1"/>
>         <section id="1-1" level="2"/>
>         <section id="1-2" level="2"/>
>         <section id="1-2-1" level="3"/>
>         <section id="1-2-2" level="3"/>
>         <section id="2" level="1"/>
>     </section>
> where the @level attribute represents the "indent" or embedding level.
>
> My question is:
> What is the best approach to transform the "flat" structure back to the
> original logical structure, with XSLT2 (Saxon), assuming that only the
> 'flat' version is received by the application?
>
> At first, it is easy to sequentially read and rebuild the sections,
> - recursing further when @level increments (embedded sections)
> - iterating further when @level remains the same (sibling sections)
>
> But the remaining issue is to manage exit from the recursion, as @levels
> come back down.
> In the example,  from section 1-2-2 to section 2 (level 3 to level 1).
>
> Note that section ids are hierarchical here only for clarity as in
> reality they would be anything.
>
> There must be a 'clean' solution to this relatively common/simple
> transformation issue.
> Any help or guidance would be appreciated.
>
> Thank you
> ac