ANN: OWL Security Ontology (plus question)

Hi Folks,

Many thanks to you for answering my questions yesterday.  Using your
suggestions I have put together a basic security ontology.  Here is a
pictorial view:

   http://www.xfront.com/owl/ontologies/security/sld001.htm

Here is the OWL ontology:

   http://www.xfront.com/owl/ontologies/security/securityLabel.owl

And here is a sample instance document:

   http://www.xfront.com/owl/ontologies/security/Document.xml

I have a question about the instance document:

Is it valid?  It shows Document having a property,
hasUnclassifiedLabel.  But this is not a property of Document, rather of
UnclassifiedThing.

I believe that it is valid.  I believe that since it contains the
hasUnclassifiedLabel property we can infer that the Document must be an
UnclassifiedDocument.  Right?  /Roger