[JDEV] XML Schema Q: How to include element from another namespace

[adamtheo at theoretic.com]

Hello, all.

I'm working on changing JEP 0038 to use a single OBJECT element as per
public demands, and read the spec of the OBJECT element from XHTML 2.0
[http://www.w3.org/TR/2002/WD-xhtml2-20021211/mod-object.html#s_objectmodule].
I have decided that the icondef.xml files in JEP 0038 will simply re-use
the OBJECT element as defined and used by XHTML 2.0, instead of creating a
variant or sub-set (although client developers are encouraged to only
implement a sub-set of the OBJECT functionality). I'm just wanting to
refer to the official XHTML 2.0 specification/schema when it comes to
defining how this OBJECT element works. How do I do this in the Schema
included with JEP 0038 that defines the structure of the icondef.xml file?
Any ideas? I'm not that familiar with XML Schema.