Firstly, the variables xpath and cxpath do not hold XPath expressions, they
hold node-sets that result from evaluating those XPath expressions. However,
I don't believe this misunderstanding is the cause of the trouble.
The problem is that key('products-by-id', @id)[1]) selects the first product
in the whole document that has a particular ID, whereas you want the first
one within some subtree of the document. Solving this problem, I'm afraid,
will take me longer than the time I allow myself for writing responses on
this list. Most of the examples of how to do this work with a fixed
hierarchy, it's more difficult with a recursive hierarchy. It becomes musch
easier in XSLT 2.0 with xsl:for-each-group because you can choose any
sequence you like as the grouping population.
Michael Kay
-----Original Message-----
From: anarkin(_at_)ntlworld(_dot_)com
[mailto:anarkin(_at_)ntlworld(_dot_)com]
Sent: 23 August 2004 10:55
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] Problem using Muenchian Method
Hi,
I'm having a problem using the 'Muenchian Method' to produce
unique output nodes. I'm sure it's not a problem with the
method, just my fumbling application of it.
Here's the XML:
<?xml version='1.0' encoding='UTF-8'?>
<?xml-stylesheet href="test.xsl" type="text/xsl"?>
<categories>
<category name='Duo'>
<product id='W110'/>
<product id='W111'/>
<product id='W112'/>
</category>
<category name='Speciality'>
<category name='Glass'>
<product id='W110'/>
<product id='W111'/>
<product id='W112'/>
</category>
<category name='Wood'>
<category name='Yew'>
<product id='W102'/>
<product id='W115'/>
</category>
<category name='Mahogany'>
<product id='W120'/>
<product id='W115'/>
</category>
</category>
</category>
</categories>
Here's the XSLT:
<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
<xsl:output
method="text"/>
<xsl:key name="products-by-id" match="@id" use="."/>
<xsl:param name="c"/>
<xsl:variable name="cxpath" select="
/categories//category[(_at_)name=$c]//product[generate-id(@id)=gene
rate-id(key('products-by-id', @id)[1])]
"/>
<xsl:variable name="xpath" select="
/categories/category//product[generate-id(@id)=generate-id(key
('products-by-id', @id)[1])]
"/>
<xsl:variable name="newline">
<xsl:text>
</xsl:text>
</xsl:variable>
<xsl:template match="/">
<xsl:choose>
<xsl:when test="$c">
<xsl:for-each select="$cxpath">
<xsl:value-of
select="@id"/><xsl:value-of select="$newline"/>
</xsl:for-each>
</xsl:when>
<xsl:otherwise>
<xsl:for-each select="$xpath">
<xsl:value-of
select="@id"/><xsl:value-of select="$newline"/>
</xsl:for-each>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
Here's what I'm trying to do:
If no $c param is passed to the stylesheet, I want the output
to be the @id attribute of every product node (but only once
per unique @id). This works fine using the xpath expression
held in $xpath.
If a $c param is passed to the stylesheet (the value of whuch
will be identical to the @name attribute of any of the
category nodes), I would like the output to be the @id
attribute of every product node which is a descendant of the
category node which has $c as the value of its @name
attribute. But again, I would like the value of each unique
@id output only once. The xpath for this is held in $cxpath.
This works for some nodes but not others. There is no problem
if $c=Duo, $c=Wood or $c=Yew. But with other nodes, the
output is either nothing at all, or some of the expected @ids
are missing. This occurs if they have already appeared in the
source xml document, or possibly because they have occured
previously in the key.
Also, I know I have overused the xpath // . This has been
mainly to simplify the above example.
Any help would be greatly appreciated. Thanks.
Pappa
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