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[@name=$c]//product[generate-id(@id)=generate-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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