namespace aware template matching

I'm trying to do some rather complicated, namespace aware XPath (XSLT1) 
template matching:

Given a structure like this, where <dynamic> could actually be any number 
(including 0) of elements in a namespace other than 'uri://ns-namespace':

<ns:root xmlns:ns="uri://ns-namespace">
    <ns:id> id from ns:root/ns:id </ns:id>
    <dynamic>
        <ns:article>
            <dynamic>
                <ns:id> id from ns:root/ns:article/ns:id </ns:id>
            </dynamic>
        </ns:article>
        <ns:issue>
            <dynamic>
                <more tags>
                   <ns:id> id from ns:root/ns:issue/ns:id </ns:id>
                </more tags>
            </dynamic>
        </ns:issue>
    </dynamic>
</ns:root>


I need a template which matches all <ns:id> elements whoose path from the 
<ns:root> node is simply 'ns:root/ns:article/ns:id'. So I need to be able 
o exclude all elements from any namespace which is not 'ns'.

What I mean is something like this: (although it doesn't work!)

<xsl:template match="ns:root/*[namespace-uri() != 
'uri://ns-namespace']/ns:article/*[namespace-uri() != 
'uri://ns-namespace']/ns:id"/>
</xsl:template>

But this doesn't match the case where there are no foreign elements (whose 
namespace is not 'ns') or more than one foreign element in between ns:root 
and ns:article or between ns:article and ns:id.


The clocest I came was:
<xsl:template match="ns:id[ancestor::ns:article/ancestor::ns:root]"/>

But this one doesn't stipulate that the ancestor::ns:article who has an 
ancestor::ns:root must be the first 'ns' ancestor we meet, so It will also 
match:

<ns:root xmlns:ns="uri://ns-namespace">
    <ns:id> id from ns:root/ns:id </ns:id>
    <dynamic>
        <ns:test>
            <ns:article>
                <ns:test2>
                    <dynamic>
                        <ns:id> id from 
ns:root/ns:test/ns:article/ns:test2/ns:id </ns:id>

How can I specify that the ancestor::ns:article element must be the first 
one we come accross when working up the acnestor chain?

any thoughts?


thanks

-- 
Tom Kirkpatrick
Web Developer - Virus Bulletin