Filter keys out of response - xslt-1.0

Question

I have an xslt sheet in which I have 2 response objects. $response1 contains a list of ids something like:
<response>
<idlist>
<id>1</id>
<id>2</id>
</idlist>
</response>
And $response2 contains a number of objects:
<response2>
<obj id="1" name="obj1"/>
<obj id="2" name="obj2"/>
<obj id="3" name="obj3"/>
<obj id="4" name="obj4"/>
</response2>
I want to make a copy of response2 but filtering out any objects where the id matches thos contained in response 1
<xsl:variable name="copy">
<xsl:copy-of select="$response2/*[not contains($response1, id)]"/>
</xsl:variable>
any ideas greatly appreciated
C

Answer 1

Given a well-formed input such as:
<root>
<response>
<idlist>
<id>1</id>
<id>2</id>
</idlist>
</response>
<response2>
<obj id="1" name="obj1"/>
<obj id="2" name="obj2"/>
<obj id="3" name="obj3"/>
<obj id="4" name="obj4"/>
</response2>
</root>
the following stylesheet:
XSLT 1.0
<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:template match="/root">
<xsl:variable name="ids" select="response/idlist/id" />
<output>
<xsl:copy-of select="response2/obj[not(#id=$ids)]"/>
</output>
</xsl:template>
</xsl:stylesheet>
will return:
<?xml version="1.0" encoding="UTF-8"?>
<output>
<obj id="3" name="obj3"/>
<obj id="4" name="obj4"/>
</output>
A better solution is to use a key to link the nodes by matching id:
XSLT 1.0
<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="id" match="id" use="." />
<xsl:template match="/root">
<output>
<xsl:copy-of select="response2/obj[not(key('id', #id))]"/>
</output>
</xsl:template>
</xsl:stylesheet>