Can rdf/xml format be used to serialize all features of OWL? Are there any situations where you would like to use owl/xml serialization over rdf/xml serialization?
I was reading a paper on SQWRL where they mentioned that there is no serialization for some OWL constructs. I searched around but couldn't find anything on this (constructs that cannot be serialized by rdf/xml).
Thank you in advance.
 O'Connor, M.J. and Das, A. "SQWRL: a Query Language for OWL" OWL: Experiences and Directions (OWLED), 6th International Workshop, Chantilly, VA, 2009.
asked 24 Aug '11, 11:49
Every OWL 2 ontology given in the OWL 2 Structural Specification (this includes all OWL 2 DL ontologies, but goes beyond) can be translated into a corresponding RDF graph via the OWL 2 Mapping to RDF Graphs. Since OWL/XML is a serialization syntax for the (abstract) OWL 2 Structural Specification, and since RDF/XML is a serialization syntax for (abstract) RDF graphs, this means that every OWL/XML document can be translated into an RDF/XML document. *) The other way round (the reverse RDF mapping from RDF to the native OWL syntax) is, however, /not/ generally possible, but is only safe for OWL 2 DL.
If outside OWL 2 DL, there are many dangers to not safely get from RDF to the native OWL 2 syntax. One example is when RDF lists are used as normal entities instead of argument lists for OWL constructs, e.g., if used for something like ":me :traveledCountries (Argentina Belarus China)". There is simply no translation rule for constructs like this in the reverse RDF mapping. Another example is when it cannot be determined for a property what the exact kind of property is: ObjectProperty, DatatypeProperty or AnnotationProperty. This is especially often the case for RDFS vocabularies, where you typically "only" have rdf:Property declarations and no additional OWL declarations. The reverse RDF mapping fails in such a case. Some tools (e.g. the OWL API) go beyond the reverse RDF mapping and try to make some "best guess" about such a property's exact entity type, but there is generally no safe way to find it out.
Finally, when would I want to use OWL/XML? I think it is the best serialization and data-exchange syntax for ontologies created with an ontology editor that applies an internal ontology representation following the OWL 2 native syntax, with the option to create ontologies beyond OWL 2 DL (which may make sense occasionally), and if one intends to use such ontologies only with ontology tools of this kind. I think, Protege4 counts as such a tool. **) One can then store and restore ontologies without any changes, while with RDF/XML, at least when outside OWL 2 DL, there are no guarantees for successful reconstruction (actually, the RDF Mapping does not even guarantee a precise reconstruction for OWL 2 DL ontologies, but only a /semantically/ equivalent reconstruction).
(* I am not going to mention that there are syntactic corner cases where RDF/XML fails to serialize an RDF graph...
(** I haven't installed Protege4 right now, so I cannot tell whether it uses OWL/XML or not, but it is probably at least an option for exporting ontologies, since it is supported by the OWL API, which is used by Protege4 internally.
answered 25 Aug '11, 14:00
Michael Schn... ♦
You sholuld take a look at this detailed answer about the different syntaxes of OWL.
answered 24 Aug '11, 12:18
Antoine Zimm... ♦
All of OWL can be serialized as RDF/XML. And I don't think the paper you cite makes claims to the contrary. Instead, it says that different tools could represent the same OWL using "slightly different" RDF. Thus, "SPARQL queries may perform differently when applied to ontologies produced by different tools".
XML serialization of OWL is designed for use by XML tools (e.g., tools using, for example, XQuery). Although the XML serialization is designed as an exchange syntax for OWL 2, RDF/XML is the only required exchange syntax for OWL.
If the above critique of SPARQL was an issue (I have not experienced these problems), chances are it could also be applied to the use of XQuery with XML serialization of OWL.