Re: [xsl] Converting milestone tags

[Michael Kay <mike@xxxxxxxxxxxx>]

 This class of problems is quite tricky. The most general approach is 
to flatten the first hierarchy, so everything is reduced to milestones, 
and then use positional grouping to construct the new hierarchy from the 
flat structure.

If you have access to a good library, try looking for Michael Jackson's 
1970s books on Jackson Structured Programming, where he tackles this 
class of problem under the heading of "boundary conflict". The 
vocabulary is different - it's all about sequential processing of 
hierarchic files on magnetic tape - but the logic is the same, and it's 
the most systematic treatment I've seen. Essentially he shows that if 
the hierarchic structure of the input and output are in some sense 
congruent, then a single tree walk over the input can handle the 
problem, but if they aren't then you can devise a new intermediate 
hierarchy - perhaps very flat - that is congruent with both the input 
and the output, so one tree walk will get you from the input to the 
intermediate tree, and a second tree walk will get you from the 
intermediate tree to the output. (This is assuming of course that you 
don't have an ordering conflict, which is true in your case).

Your example doesn't need the full generality of this approach, because 
the start/end milestones are always siblings and are always matched in 
the same paragraph, but your discussion indicates that you might want to 
tackle things that go beyond this example.

Michael Kay
Saxonica

On 14/10/2010 8:05 AM, Josef Schneeberger wrote:
> Hi everybody,
>
> I am new to this list and apologize, if my question is an FAQ. I scanned
> the archives, but did not find a solution. The question arises in a TEI
> project where we have to switch from a chapter hierarchy to a page
> oriented form. The XSLT is done in multiple steps (a cocoon pipeline)
> and I use Saxon9.
>
> Here is a simplified example of an infile:
>
> <root>
>   <p>text<span order="start"/>text<span order="end"/>  text</p>
>   <p>text<span order="start"/>text<span order="end"/>  text
>      text<span order="start"/>text<span order="end"/>  text</p>
>   <p>text text text<span order="start"/>text<span order="end"/></p>
>   <p><span order="start"/>text<span order="end"/>  text text text</p>
> </root>
>
> which should result in the following output:
>
> <root>
>   <p>text<span>text</span>  text</p>
>   <p>text<span>text</span>  text
>      text<span>text</span>  text</p>
>   <p>text text text<span>text</span></p>
>   <p><span>text</span>  text text text</p>
> </root>
>
> There my be an arbitrary number of<span order="begin"/>  (and
> corresponding end milestone tags) in a p element. Furthermore, any
> "text" node may again contain markup which should be preserved in the
> output. I tried various approaches but I failed. Here is one of my
> attempts using sibling recursion ...
>
> <xsl:stylesheet version="2.0"
>   xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
>   <xsl:template match="/">
>    <xsl:apply-templates/>
>   </xsl:template>
> 	
>   <xsl:template match="root">
>    <root><xsl:apply-templates/></root>
>   </xsl:template>
> 	
>   <xsl:template match="p">
>    <p>
>     <xsl:apply-templates select="child::node()" mode="procp"/>
>    </p>
>   </xsl:template>
> 	
>   <xsl:template match="span[@order='start']" mode="procp">
>    <span>
>     <xsl:apply-templates
>       select="following-sibling::node()[1][not(self::span)]"
>       mode="procp"/>
>    </span>
>    <xsl:apply-templates select="following-sibling::node()[1]"/>
>   </xsl:template>
> 	
>   <xsl:template match="node()" mode="procp">
>    <xsl:copy-of select="."/>
>     <xsl:apply-templates
>        select="following-sibling::node()[1][not(self::span)]"
>        mode="procp"/>
>   </xsl:template>
> </xsl:stylesheet>
>
> Any help would be greatly appreciated. Josef