And libxslt has the exslt extension.
Sorry Daniel.

See http://mail.gnome.org/archives/xslt/2002-May/msg00063.html

(and It also implements most of the EXSLT set of processor-portable
extensions functions and some of Saxon's evaluate and expressions
extensions. from http://xmlsoft.org/XSLT/)

regards DaveP

    <!-- Use nodeset as an XSLTC extension function -->
    <xsl:value-of select="xsltc-extension:nodeset($rtf)/docelem/elem1"/>
    <!-- Use nodeset as a Xalan-Java extension function -->
    <xsl:value-of select="xalan:nodeset($rtf)/docelem/elem1"/>
    <!-- Use nodeset as an EXSLT extension function -->
    <xsl:value-of select="exslt:node-set($rtf)/docelem/elem1"/>
    <!-- Use nodeset as standard function -->
    <xsl:value-of select="nodeset($rtf)/docelem/elem1"/>