RE: RDF Extensibility

>-----Original Message-----
>From: []
>On Behalf Of Ian Davis
>Sent: Tuesday, July 06, 2010 5:53 PM
>To: Dan Brickley
>Cc: Jiří Procházka; Toby Inkster; Michael Schneider; Linked Data
>community; Semantic Web; Pat Hayes
>Subject: Re: RDF Extensibility
>2010/7/6 Dan Brickley <>:
>> 2010/7/6 Jiří Procházka <>:
>>>> It would have a meaning. It would just be a false statement. The
>>>> same as the following is a false statement:
>>>>       foaf:Person a rdf:Property .
>>> Why do you think so?
>>> I believe it is valid RDF and even valid under RDFS semantic
>>> Maybe OWL says something about disjointness of RDF properties and
>>> URI can be many things.
>> It just so happens as a fact in the world, that the thing called
>> foaf:Person isn't a property. It's a class.
>I think that is your view and the view you have codified as the
>authoritative definition that I can look up at that URI, but there is
>nothing preventing me from making any assertion I like and working
>with that in my own environment. If it's useful to me to say
>foaf:Person a rdf:Property then I can just do that. However, I
>shouldn't expect that assertion to interoperate with other people's
>views of the world.

If one has some constraint like this in mind, one should consider trying to
make it explicit when creating the ontology. In the cited messages above, I
am reading: 

  "Maybe OWL says something about disjointness 
  of RDF properties and classes." 

Well, this is /not/ the case, but one could have explicitly stated:

  foaf:Person rdf:type [ owl:complementOf rdf:Property ] .

as an additional axiom in FOAF (and likewise for other classes, if desired),
or more generically:

  rdfs:Class owl:disjointWith rdf:Property .

Of course, this is not in OWL DL, but FOAF is outside OWL DL, anyway, due to
its inverse-functional data properties. However, the above is in OWL Full
(as FOAF is), and also within the scope of the OWL 2 RL/RDF Rules. So, under
these entailment regimes, if one asserts the statements:

  foaf:Person rdf:type rdfs:Class . 
  foaf:Person rdf:type rdf:Property .

this then leads to a semantic inconsistency (with either of the two
alternatives given above). And there are a number of reasoners around which
are able to detect these kinds of inconsistencies, e.g.:



Dipl.-Inform. Michael Schneider
Research Scientist, Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
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Received on Tuesday, 13 July 2010 10:25:29 UTC