XInclude from sources different than Docbook or text files

["Zbyszek Cybulski" <z.cybulski@gmail.com>]

Hi list,

I have a need to include content that is in an XML file, which is not
Docbook. I have tried to get it working in different ways, but finally
failed. For example:

<para>
<xi:include href="external-data.xml" xpointer="element(/1/1/2)"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
</para>

works, but this is not satisfactory to me. I need to refer to external
elements by their IDs. So, I have tried the following:

<para>
<xi:include href="external-data.xml"
xpointer="element(/Name/Identity[@id='conRef']/Description)"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
</para>

and

<para>
<xi:include href="../../../../terminology/terminology.xml"
xpointer="element(conRef)"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
</para>

and

<para>
<xi:include href="../../../../terminology/terminology.xml"
xpointer="xpointer(id('conRef'))"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
</para>

and

<para>
<xi:include href="../../../../terminology/terminology.xml"
xpointer="conRef" xmlns:xi="http://www.w3.org/2001/XInclude"/>
</para>

None of them worked.
Can I include such a content without running an XSLT transformation
the external source to convert it to Docbook? Any help is appreciated.

Regards,

-Zbyszek