Xslt transform & grouping, Using the Muenchian Method?

Hi,

I would like to group following, by attribute Title, and then filter
by attribute filter="food". Title-attribute exists in both Document
and Article elements.

That is, groups should be created based on attribute Title in Document
element, and filtered by attribute e.g. filter="food".

Currently I am using grouping and filtering in following stylesheet.

All other elements, where filter != "food" should be ignored.
Filter is global parameter.

Thank you!


Some help on the way:

XSL:

<?xml version='1.0' encoding='UTF-8'?>

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

<xsl:key name="by-info" match="Article" use="@info"/>

<xsl:param name="filter" select="'food'"/>

<xsl:template match="Documents">
	<Documents>
		<xsl:for-each select="Document[@filter='' or
@filter=$filter]/Article[generate-id()=generate-id(key('by-info',@info)[@filter=$filter])]">
			<Document name="{@info}">
				<xsl:copy-of select="key('by-info',@info)[@filter=$filter]"/>
			</Document>
		</xsl:for-each>
	</Documents>
</xsl:template>

</xsl:stylesheet>


XML:

<Documents>
	<Document title="1" chapter="1" href="file1.xml" filter="food">
		<Article title="1.1" info="sub" filter="food"/>
		<Article title="1.2" info="main" filter="food"/>
	</Document>
	<Document title="2" chapter="2" href="file2.xml" filter="drink">
		<Article title="2.1" info="sub" filter="drink"/>
		<Article title="2.2" info="main" filter="food"/>
	</Document>
	<Document title="3" chapter="3" href="file2.xml" filter="">
		<Article title="3.1" info="sub" filter="drink"/>
		<Article title="3.2" info="child" filter=""/>
	</Document>
</Documents>


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[row.filter]