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Re: Generic Lookup (Element Mapping)
- From: "G. Ken Holman" <gkholman at CraneSoftwrights dot com>
- To: <XSL-List at lists dot mulberrytech dot com>
- Date: Tue, 07 May 2002 11:23:38 -0400
- Subject: Re: [xsl] Generic Lookup (Element Mapping)
- Reply-to: xsl-list at lists dot mulberrytech dot com
At 2002-05-07 08:15 -0500, Faroukh Fekravar wrote:
>I have been trying to write a generic xslt template to map the element names
>based on a lookup table.
Is there a reason you want to do this in one stylesheet with both the
mapping file and the data file?
>The lookup xml file has always a subset of the elements and therefore I do
>not want to hard code the element names.
Then you need a customized stylesheet based on your mappings, especially
for speed in order to do a single pass on the input data.
>The output file is a flat xml file in opposite to the input file.
This was a particularly difficult criterion to meet.
>But my main problem is how navigate through the input file in a generic
>approach.
>I'm also just a little concern about the overall performance because the
>input file might be MBs big.
For performance reasons, I recommend you write a stylesheet that, based on
your mapping, emits a single stylesheet that is then run against your
data. This emitted stylesheet does simple matches and should meet your
performance requirements.
An example of writing a stylesheet that writes a stylesheet is in Chapter 5
of "Definitive XSLT and XPath" which happens to be the freely-downloadable
chapter made available by Prentice Hall on the Amazon site. It is also in
Chapter 5 of our electronic book from which the paper book was derived.
A working answer to your requirements is below.
I hope this helps.
...................... Ken
t:\ftemp>type data.xml
<?xml version="1.0" encoding="iso-8859-1"?>
<project>
<aa1>
<aa11>aa11_value</aa11>
<aa12>aa12_value</aa12>
<aa13>aa13_value</aa13>
<aa2>
<aa21>aa21_value</aa21>
<aa22>aa22_value</aa22>
<aa3>
<aa31>aa31_value</aa31>
<aa4>
<aa41>aa41_value</aa41>
</aa4>
</aa3>
</aa2>
</aa1>
</project>
t:\ftemp>type lookup.xml
<?xml version="1.0" encoding="iso-8859-1"?>
<Maps>
<Map> <!-- combination
of SEName, SAname and TEname is unique through
the file.-->
<SEname>aa1</SEname> <!-- element name in the
input file-->
<SAname>aa11</SAname> <!-- element name in the
input file, it's always
the child element of SEName-->
<TEname>aa_1</TEname> <!-- element name in output-->
<TAname>aa_11</TAname> <!-- element nemae in
output, it should be the
child element of TEname-->
</Map>
<Map>
<SEname>aa1</SEname>
<SAname>aa12</SAname>
<TEname>aa_1</TEname>
<TAname>aa_12</TAname>
</Map>
<Map>
<SEname>aa1</SEname>
<SAname>aa13</SAname>
<TEname>aa_1A</TEname>
<TAname>aa_13</TAname>
</Map>
<Map>
<SEname>aa2</SEname>
<SAname>aa21</SAname>
<TEname>aa_2</TEname>
<TAname>aa_21</TAname>
</Map>
<!-- no mapping for aa22 -->
<Map>
<SEname>aa3</SEname>
<SAname>aa31</SAname>
<TEname>aa_3</TEname>
<TAname>aa_31</TAname>
</Map>
</Maps>
t:\ftemp>type faroukh.xsl
<?xml version="1.0" encoding="iso-8859-1"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xslo="junk"
version="1.0">
<xsl:namespace-alias stylesheet-prefix="xslo" result-prefix="xsl"/>
<xsl:key name="parents" match="Map" use="SEname"/>
<xsl:key name="children" match="Map" use="concat(SEname,' ',TEname)"/>
<xsl:template match="/">
<xslo:stylesheet version="1.0">
<xslo:output indent="yes"/>
<xslo:template match="/project"><!--preserve project element-->
<project>
<xslo:apply-templates/>
</project>
</xslo:template>
<xslo:template match="*"/><!--throw away unmapped-->
<xslo:template match="text()"/><!--only keep explicitly copied text-->
<xsl:apply-templates/>
</xslo:stylesheet>
</xsl:template>
<xsl:template match="Map">
<!--only put out a single template for the
parent-->
<xsl:if test="generate-id(.)=generate-id(key('parents',SEname))">
<xslo:template match="{SEname}">
<!--needs as many apply templates as unique parent
mappings-->
<xsl:for-each select="key('parents',SEname)[generate-id(.)=
generate-id(key('children',concat(SEname,'
',TEname)))]">
<xslo:element name="{TEname}">
<xslo:apply-templates mode="mapping">
<xsl:attribute name="select">
<xsl:for-each select="key('children',concat(SEname,'
',TEname))">
<xsl:if test="position()>1">|</xsl:if>
<xsl:value-of select="SAname"/>
</xsl:for-each>
</xsl:attribute>
</xslo:apply-templates>
</xslo:element>
</xsl:for-each>
<xslo:apply-templates/>
</xslo:template>
</xsl:if>
<xslo:template match="{SEname}/{SAname}" mode="mapping">
<xslo:element name="{TAname}">
<xslo:value-of select="."/>
</xslo:element>
</xslo:template>
</xsl:template>
</xsl:stylesheet>
t:\ftemp>saxon -o mapping.xsl lookup.xml faroukh.xsl
t:\ftemp>saxon -o faroukh.out data.xml mapping.xsl
t:\ftemp>type faroukh.out
<?xml version="1.0" encoding="utf-8"?>
<project>
<aa_1>
<aa_11>aa11_value</aa_11>
<aa_12>aa12_value</aa_12>
</aa_1>
<aa_1A>
<aa_13>aa13_value</aa_13>
</aa_1A>
<aa_2>
<aa_21>aa21_value</aa_21>
</aa_2>
<aa_3>
<aa_31>aa31_value</aa_31>
</aa_3>
</project>
t:\ftemp>rem Done!
--
Upcoming: 3-days XSLT/XPath and/or 2-days XSLFO: June 17-21, 2002
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Crane Softwrights Ltd. http://www.CraneSoftwrights.com/s/
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