[xsl] build a select clause or dynamic URI's

[Andy Dent <dent@xxxxxxxxxxxxx>]

I'm trying to construct some generic XSLT patterns for processing
typical GML documents and am struggling with a dynamic path following
issue. I've over 20 years in software development and a moderate XSLT
semantic understanding but am not yet at guru level. The num2cells
template at the end of this message is about as good as I've got :-)

I don't know if this is possible in generic XSLT. As these are 
samples expected to be used by a wide community, I'm trying to avoid 
extensions.

I summarise what I need as wanting to go from a string value in an
attribute to having the nodeset it refers to. So, given an href like
"../../../gml:position" I can write a generic template to invoke the
original gml:position template.

I've experimented with the document function and just had someone 
else suggest it may help but I'm not sure how to use document to 
refer to a different location in the current source.

Say we have some XML with a relative ref back in the file, like:
             <featureMember>
                         <GeochemSpecimen gml:id="WA_1_139459">
                                     <gml:name>139459</gml:name>
                                     <gml:position
xlink:href="urn:x-seegrid:definition:gml:NilReason:unknown"/>
                                     <material>rock</material>
                                     <relatedObservation>
                                                 <GeochemMeasurement
gml:id="WA_1_139459_Ag">

<gml:position xlink:href="../../../gml:position"/>


I'm processing this with <xsl:apply-templates select="gml:position"/>
invoking the following

             <xsl:template match="gml:position">
                         <xsl:choose>
                                     <xsl:when
test="contains(@xlink:href,'gml:position')">
                                     <!-- ref to another position, eg:
@xlink:href='../../../gml:position'-->
<!-- literal select works     <xsl:apply-templates
select='../../../gml:position'/> -->
                                     </xsl:when>
                                     <xsl:when
test="@xlink:href='urn:x-seegrid:definition:gml:NilReason:unknown'">
                                                 <td
colspan="3">unknown</td>
                                     </xsl:when>
                                     <xsl:when test="gml:Point/gml:pos">
                                                 <xsl:call-template
name="num2cells">

<xsl:with-param name="numbers"
select="normalize-space(gml:Point/gml:pos)"/>

<xsl:with-param
name="colsToFill" select="3"/>
                                                 </xsl:call-template>
                                     </xsl:when>
                                     <xsl:otherwise>
                                                 <td
colspan="3">unrecognised gml:position</td>
                                     </xsl:otherwise>
                         </xsl:choose>
             </xsl:template>


             <!-- Recursively parse a space-delimited list into <td>
pairs, assumes single whitespace delimiters, puts colspan on blank last
entry if necessary, pass in 0 to colsToFillif don't care about padding
-->
             <xsl:template name="num2cells">
                         <xsl:param name="numbers"/>
                         <xsl:param name="colsToFill"/>
                         <xsl:choose>
                                     <xsl:when test="contains($numbers,'
')">
                                                 <td>

<xsl:value-of select="substring-before($numbers, ' ')"/>
                                                 </td>
                                                 <xsl:call-template
name="num2cells">

<xsl:with-param name="numbers" select="substring-after($numbers, ' ')"/>

<xsl:with-param
name="colsToFill" select="number($colsToFill)-1"/>
                                                 </xsl:call-template>
                                     </xsl:when>
                                     <xsl:when test="$colsToFill>2">
                                                 <td><xsl:value-of
select="$numbers"/></td><td colspan="{$colsToFill-1}">&nbsp;</td>
                                     </xsl:when>
                                     <xsl:when test="$colsToFill=2">
                                                 <td><xsl:value-of
select="$numbers"/></td><td>&nbsp;</td>
                                     </xsl:when>
                                     <xsl:otherwise> <!-- exact fit or
more cols thanexpected -->
                                                 <td><xsl:value-of
select="$numbers"/></td>
                                     </xsl:otherwise>
                         </xsl:choose>
             </xsl:template>


Thanks for any advice


--

Andy Dent BSc  MACS   http://www.oofile.com.au/
OOFILE - Database, Reports, Graphs, GUI for c++ on Mac, Unix & Windows
PP2MFC - PowerPlant->MFC portability