RE: [xsl] variables vs. modes

["Michael Kay" <mike@xxxxxxxxxxxx>]

I tend to use this approach quite heavily, of structuring the processing as
a sequence of variables, each one of which is derived from the one before.
It's like a miniature pipeline. Some people use the same technique but using
local variables within a containing template, rather than using global
variables.

However, as soon as you have more than one step in your pipeline that can
benefit from the flexibility of apply-templates, you need to think in terms
either of multiple modes within a single stylesheet, or multiple stylesheets
connected in a pipeline.

Incidentally I've had some brief exposure recently to Orbeon as a pipeline
processor for stringing together transformations, and it's well worth a
look.

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

> -----Original Message-----
> From: Bruce D'Arcus [mailto:bdarcus@xxxxxxxxxxxxx] 
> Sent: 25 November 2004 22:03
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] variables vs. modes
> 
> I'm considering reworking my (2.0) stylesheets towards 
> greater reliance 
> on global variables.
> 
> In my current approach, I use multiple passes, with multiple modes.  
> However, I feel that it may make more sense (be more flexible, easier 
> to integrate with other stylesheets and to maintain, etc.) to use 
> variables instead.  Below is a simple example of what I mean.
> 
> Are there any counter-arguments I may be missing before I actually do 
> this?
> 
> Bruce
> 
> <?xml version="1.0" encoding="utf-8"?>
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; 
> version="2.0"
>     xmlns:mods="http://www.loc.gov/mods/v3";
>     xmlns:db="http://docbook.org/docbook-ng";
>     xmlns:exist="http://exist.sourceforge.net/NS/exist";
>     exclude-result-prefixes="db mods exist">
> 
>     <xsl:output method="xml" encoding="utf-8" indent="yes"/>
> 
> <!-- grab all the citation pointers -->
>     <xsl:variable name="citerefs" select="//db:biblioref/@linkend"/>
> 
> <!-- construct a list of unique references to pass to a query -->
>     <xsl:variable name="citekeys">
>       <xsl:text>(</xsl:text>
>         <xsl:for-each-group select="$citerefs" group-by=".">
>           <xsl:if test="position() &gt; 1">,%20</xsl:if>
>           <xsl:text>'</xsl:text>
>           <xsl:value-of select="."/>
>           <xsl:text>'</xsl:text>
>         </xsl:for-each-group>
>       <xsl:text>)</xsl:text>
>     </xsl:variable>
> 
> <!--
> take list of references, and grab them from a database over http; in 
> this case it's an XQuery to eXist,
> but it should be parameterized for flexibility
> -->
>     <xsl:variable name="bibrecord"
> 	
> select='doc(concat("http://localhost:8080/exist/servlet/db/biblio?";,
> 		
> "_query=declare%20namespace%20mods=%22http://www.loc.gov/mods/v3%22;";,
> 		"%20for%20$citekey%20in%20",
>          		$citekeys,
> 		
> "%20return%20/mods:modsCollection/mods:mods[@ID=$citekey]"))' />
> <!--
> create raw bib collection; in a real implementation, this 
> might be where
> enhancement (grouping, sorting, adding content for processing, etc.) 
> would take place
> -->
>     <xsl:variable name="raw-biblist">
>       <mods:modsCollection>
>         <xsl:copy-of select="$bibrecord/exist:result/mods:mods" />
>       </mods:modsCollection>
>     </xsl:variable>
> 
> <!-- take raw biblist and format it -->
>     <xsl:variable name="formatted-biblist">
>       <xsl:for-each 
> select="$raw-biblist/mods:modsCollection/mods:mods">
>         <p id="{@ID}">
>           <xsl:apply-templates select="mods:titleInfo"/>
>         </p>
>       </xsl:for-each>
>     </xsl:variable>
> 
>     <xsl:template match="/">
>       <div id="bibliography">
>         <xsl:copy-of select="$formatted-biblist"/>
>      </div>
>     </xsl:template>
> 
>     <xsl:template match="mods:titleInfo">
>       <span class="title">
>         <xsl:apply-templates select="mods:title"/>
>         <xsl:apply-templates select="mods:subTitle"/>
>       </span>
>     </xsl:template>
> 
>     <xsl:template match="mods:title">
>       <xsl:value-of select="."/>
>     </xsl:template>
> 
>     <xsl:template match="mods:subTitle">
>       <xsl:text>: </xsl:text>
>       <xsl:value-of select="."/>
>     </xsl:template>
> 
> </xsl:stylesheet>