Re: [xsl] building a nodeset from selected nodes

Subject: Re: [xsl] building a nodeset from selected nodes
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>
Date: Wed, 04 Jul 2001 19:00:33 +0100

If I read you right, this is a classic case for keys. We use them so much for grouping that we forget what they do, really.

<xsl:key name="columns-by-name" match="table/column" use="name"/>

then, in a template (or for-each):

<xsl:template match="table/query">
  <xsl:for-each select="key('columns-by-name', column)"> what you're going to do for each table/column
     'called' by the query...

Try it out. The select expression could also be in an xsl:apply-templates.

Hope that helps,

At 07:52 PM 7/4/01, you wrote:
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
appear to support the nodeset() extension.

For example, given the input:



When I process the "query" elements, I'd like to construct a node-set which
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',

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"/>
        ... <!-- I'd like to have the node-set here -->

<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:when test="not($rest)">
            <xsl:for-each select="$newnodes">
                <xsl:value-of select="."/>
            <xsl:call-template name="get-column-nodes">
                <xsl:with-param name="nodes" select="$newnodes"/>
                <xsl:with-param name="columns" select="$rest"/>

Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.      
17 West Jefferson Street                    Direct Phone: 301/315-9635
Suite 207                                          Phone: 301/315-9631
Rockville, MD  20850                                 Fax: 301/315-8285
  Mulberry Technologies: A Consultancy Specializing in SGML and XML

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