[xsl] building a nodeset from selected nodes

["Hall, Kurt" <khall at hsacorp dot net>]

As is often the case, I found a solution while preparing this post to
ask for help.  I think there may be a simpler solution however (using
XPATH/predicates?), plus I'd like to be able to encapsulate my solution 
in a call-template so I can reuse it.   (As a newby I'd appreciate
any other recommendations on usage, robustness, performance, etc.).

I'm trying to generate a node-set from my input where the selection
is specified by a list of elements.  Complicating matters somewhat is that
the company I'm consulting for is using an older version of xalan that
doesn't
appear to support the nodeset() extension.

For example, given the input:

	<table>
	   <column>
	      <name>A</name>
 	      <type>int</type>
 	   </column>
	   <column>
	      <name>B</name>
 	      <type>long</type>
 	   </column>
	   <column>
	      <name>C</name>
 	      <type>double</type>
 	   </column>
	   <column>
	      <name>D</name>
 	      <type>string</type>
 	   </column>
	   ...

	   <query>
	      <column>A</column>
	      <column>C</column>
	   </query>
	   <query>
	      <column>B</column>
	      <column>C</column>
	   <query>
	   ...
	</table>

When I process the "query" elements, I'd like to construct a node-set which
contains
only nodes 'A' and 'C' (and their children), do something with those nodes,
then process
the next "query" which contains 'B' and 'C'. etc.

In psuedo-SQL, this would be like "SELECT * FROM nodes WHERE name IN ('A',
'C')".

Here's the xsl I've come up with so far:

     ...
     <xsl:for-each select="table/query">
        <xsl:call-template name="get-column-nodes">
            <xsl:with-param name="nodes" select="/.."/>     <!-- create an
empty node-set -->
            <xsl:with-param name="columns" select="column"/>
        </xsl:call-template>
        ... <!-- I'd like to have the node-set here -->
     </xsl:for-each>
     ...

<xsl:template name="get-column-nodes">
    <xsl:param name="nodes"/>
    <xsl:param name="columns"/>
    <xsl:if test="$columns">
        <xsl:variable name="col" select="$columns[1]"/>
        <xsl:variable name="new" select="//table/column[name=$col]"/>
        <xsl:variable name="newnodes" select="$nodes | $new"/>
        <xsl:variable name="rest" select="$columns[position()!=1]"/>
        <xsl:choose>
        <xsl:when test="not($rest)">
            DO SOMETHING WITH THESE NODES...
            <xsl:for-each select="$newnodes">
                <xsl:value-of select="."/>
            </xsl:for-each>
            DONE
        </xsl:when>
        <xsl:otherwise>
            <xsl:call-template name="get-column-nodes">
                <xsl:with-param name="nodes" select="$newnodes"/>
                <xsl:with-param name="columns" select="$rest"/>
            </xsl:call-template>
        </xsl:otherwise>
        </xsl:choose>
    </xsl:if>
</xsl:template>

Thanks much for any help.
-kurt


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