- From: Henry Story <henry.story@bblfish.net>
- Date: Thu, 23 Mar 2006 16:36:35 +0100
- To: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Cc: brian.mcbride@hp.com, larsga@ontopia.net, semantic-web@w3.org
On 23 Mar 2006, at 15:58, Peter F. Patel-Schneider wrote:
> Date: Thu, 23 Mar 2006 13:47:17 -0000
>>>
>>> I don't understand the difference. RDF just does not have the
>>> expressive
>>> power to do this sort of thing. It just like asking whether
>>> propositional
>>> logic could express something like "All students are people."
>>
>> I think that answers my question.
>> I'm confused about how semantics of [OWL] relate to the semantics
>> of RDF.
>
> Roughly in the way that propositional logic relates to predicate
> logic (at
> least if you think of propositional logic in a certain way). There
> are
> "more" constructs in OWL, and these constructs have meaning that
> cannot be
> expressed in RDF. The only strangeness is that the extra OWL
> constructs
> are actually written as (collections of) RDF triples, but
> nonetheless the
> added expressive power is still real.
I hope that is wrong. My understanding is rather that RDF gives you a
framework.
OWL just gives you specialised relations with certain specific
inferential properties.
So if you take the relation owl:inverseOf then this is just an rdf
relation.
But it is linked to the following well known rule:
{ ?r1 owl:inverseOf ?r2 .
?a ?r1 ?b . } => { ?b ?r2 ?a . } .
All of the owl vocabulary can be defined in terms of such rules. The
OWL terms have been very carefully selected to make certain types of
inferencing easier. But otherwise OWL just is a specialised vocabulary.
Henry
Received on Thursday, 23 March 2006 15:36:48 UTC