> Thanks for any tips how to improve performance..

> <xsl:variable name="identifier">
>    <xsl:value-of select="normalize-space(dc:identifier)"/>
> </xsl:variable>

Never use an xsl:variable with content like this unless you really need
to generate a new result tree fragment 9which is essentially a new node
tree with a root node (/) a text node with string value. that's
expensive to build and has to be coersed back to a string when used. You
just want a string here so

 <xsl:variable name="identifier">
   select="normalize-space(dc:identifier)"/>

which is less code to type and a lot more efficient (athough in this
case you don't really need a variable at all). In xslt1 that will use
the first dc:identifier, in xslt2 it will generate an error that there
is more than one. Tou sie the second you can use

 <xsl:variable name="identifier">
   select="normalize-space(dc:identifier[2])"/>

or [last()] or whatever predicate you need to specify.


  <rdf:Description>
	<xsl:attribute name="rdf:about"><xsl:value-of 
select="$identifier"/></xsl:attribute>

could be written more simply as
  <rdf:Description rdf:about="{$identifier}">
or just inline the variable if it is only used once:

  <rdf:Description rdf:about="{normalize-space(dc:identifier[2]}">

David