OWL DL work-arounds instead of imports?

Question

I'm learning how to use the Good relation ontology in particular, together with the Product type ontology that it recommend as a basic ontology to further describe/type your goods: http://www.productontology.org/

Looking at how the product type ontology work i retrieved its RDF for the type book: That is i requested http://www.productontology.org/id/Book with a MIME RDF+XML. I then Get to the following file http://www.productontology.org/doc/Book.rdf

Now here is my question. I do not understand the following at the head of the ontology.

<-- OWL DL work-arounds instead of imports -->

<owl:AnnotationProperty rdf:about="http://purl.org/dc/elements/1.1/title" />
<owl:AnnotationProperty rdf:about="http://purl.org/dc/elements/1.1/subject" />
<owl:AnnotationProperty rdf:about="http://purl.org/dc/elements/1.1/creator" />
<owl:AnnotationProperty rdf:about="http://purl.org/dc/terms/license" />
<owl:AnnotationProperty rdf:about="http://purl.org/dc/elements/1.1/rights" />
<owl:AnnotationProperty rdf:about="http://purl.org/dc/elements/1.1/contributor" />
<owl:Class rdf:about="http://xmlns.com/foaf/0.1/Document" />
<owl:AnnotationProperty rdf:about="http://xmlns.com/foaf/0.1/primaryTopic" />
<owl:AnnotationProperty rdf:about="http://xmlns.com/foaf/0.1/page" />
<owl:AnnotationProperty rdf:about="http://xmlns.com/foaf/0.1/homepage" />
<owl:AnnotationProperty rdf:about="http://www.w3.org/2007/05/powder-s#describedby" />
<owl:Class rdf:about="http://schema.org/Product" />

<-- OWL 1 DL compatibility of the OWL2 deprecated property -->

<owl:AnnotationProperty rdf:about="http://www.w3.org/2002/07/owl#deprecated" />

That's it i would like to understand the prupose of this workaround. My guess is that, in OWL you can't just import a namespace and use its properties as is.... But then what about rdfs, rdf namespace.... Hence my question. Can someone Help ?

Answer 1

The issue is not related to the namespaces. What this ontology is doing is declaring some annotation properties instead of importing the ontology that already defines them.

The reason for doing so is that the rest of that ontology does not conform tho the OWL 2 DL profile, and importing it would make the goodrelations ontology be OWL 2 Full as well.

Namespaces are not limited in ontologies: any on to go can define a class or a property in any namespace. Keeping the ontology prefix synchronised with the entities prefixes is only a convention, not an obligation.