Implement <xsl:key>

[menelai]

Should work this way:

<xsl:key name="term-key" match="mark" use="concat(@term, ../../@id)"/>
<xsl:template match="marks">
  <xsl:variable name="unique-term" select="mark[generate-id()=generate-id(key('term-key', concat(@term, ../../@id)))]/@term"/>
</xsl:template>

Thank you

[tenaz3]

I had the same issue when I try to combine xml and stylesheet from nmap(https://svn.nmap.org/nmap/docs/nmap.xsl)