RE: grouping (was: if or template?)

Subject: RE: grouping (was: if or template?)
From: "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 12 May 2000 18:24:57 +0200
(I wrote this post before finding Steve's example just now from Wednesday in my archive; I'll still post it since it is what I did this evening for myself to help me understand what he has developed. I think this is quite neat!)

At 00/05/08 17:54 +0100, Kay Michael wrote:
> I want to then display the Tracker_ID if it is unique followed by all the
data for
> the specific tracker.

A FAQ: use something like
<xsl:for-each select="//tracker-id[not(.=preceding::tracker-id)]">

This is the traditional solution; Steve Muench has just told me about a
brilliant alternative using keys:

<xsl:key name="tid" use="tracker-id" select="."/>


I hope Steve will forgive me for announcing this discovery before he does,
I'm quite excited by it because it gives much better performance.

This is a truly kewl idea ... but ... isn't the syntax above incorrect?

Wouldn't the declaration of the key be as follows?

<xsl:key name="tid" match="tracker-id" use="."/>

I apologize in advance if this sounds pedantic, but readers might get confused about which attribute is the matching attribute (match=) and which is the selection (use=) since the cited example had it backwards and incorrectly named.

I have an example below.

I hope this helps.

................... Ken

T:\ftemp>type tests.xml <?xml version="1.0"?> <names> <name><given>Julie</given><surname>Holman</surname></name> <name><given>Margaret</given><surname>Mahoney</surname></name> <name><given>Ted</given><surname>Holman</surname></name> <name><given>John</given><surname>Mahoney</surname></name> <name><given>Kathryn</given><surname>Holman</surname></name> <name><given>Ken</given><surname>Holman</surname></name> </names> T:\ftemp>type tests.xsl <?xml version="1.0"?> <xsl:stylesheet xmlns:xsl=""; version="1.0">

<xsl:output method="text"/>

            <!--prepare to examine all names valued by surname-->
<xsl:key name="surnames" match="name" use="surname"/>

<xsl:template match="/">                         <!--root rule-->
            <!--select only those name elements whose unique
                generated id is equal to the generated id of the
                first of the key members with the same surname-->
    <xsl:value-of select="surname"/>     <!--show the grouping-->
                        <!--select only those for the grouping-->
    <xsl:for-each select="//name[surname=current()/surname]">
      <xsl:sort select="given"/>    <!--sorted within grouping-->
      <xsl:text>   </xsl:text>
      <xsl:value-of select="given"/>   <!--member distinctions-->


T:\ftemp>saxon tests.xml tests.xsl

-- G. Ken Holman mailto:gkholman@xxxxxxxxxxxxxxxxxxxx Crane Softwrights Ltd. Box 266, Kars, Ontario CANADA K0A-2E0 +1(613)489-0999 (Fax:-0995) Web site: XSL/XML/DSSSL/SGML services, training, libraries, products. Practical Transformation Using XSLT and XPath ISBN 1-894049-04-7 Next instructor-led training: 2000-05-11/12,2000-05-15, - 2000-06-12,2000-06-13,2001-01-27

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