Catalogs put much less focus on the instance's construction.

Example:

<e:event xmlns:e="urn:publicid:IDN+cde.berkeley.edu:milowski:schemas:example-form:event:200402">
...
</e:event>

and the catalog has the mapping information:

<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog" prefer='public'>   
<public publicId="IDN cde.berkeley.edu//milowski//schemas//example-form//event//200402" 
            uri="event.xsd"/>
</catalog>