How to include Non-OWL elements?

Hi!

I don't really know where to ask this question, so I do it here.

I want to include additional application-specific information into my OWL document. So I declared a namespace xmlns:foo="http://www.bar.com/foo#" and included an element <foo:something/> into my ontology. I hoped that OWL-applications would ignore elements which don't belong to OWL, but the validator at http://owl.bbn.com/validator/ gave me errors. Is there a way to include non-OWL elements?

Regards, Patric