Re: Interpretation of RDF reification

On 23 Mar 2006, at 16:44, Peter F. Patel-Schneider wrote:
>> I hope that is wrong.
> Nope, it is correct.

What do you base you position on?

>> My understanding is rather that RDF gives you a
>> framework.
> Well, just *what* is a framework?

It states the basic elements and how they can be put together.

>> OWL just gives you specialised relations with certain specific
>> inferential properties.
> Not really.  OWL in RDF gives you much more than specialized  
> relations.
> Much of the power of OWL comes from syntax that is more than just  
> single
> relations.  It so happens that it is possible to embed OWL in RDF in a
> certain manner.  (This is not always possible, by the way, and OWL  
> is very
> close to the maximum expressiveness that can be so embedded in RDF.)

I don't think anything in OWL depends on the syntax. I can write own  
triples in rdf/xml,
N3, Turtle, etc...

>> So if you take the relation owl:inverseOf then this is just an [RDF]
>> relation.
> Well, sure, owl:inverseOf is *just* an RDF property, in RDF.  In  
> OWL, on
> the other hand, owl:inverseOf is a special property - it has a extra
> meaning provided by the OWL semantics.

This is where it would be interesting to understand if this  
difference in semantics is
complementary or widely different. My guess is that it is  
complimentary. owl relations
have special semantics, just as the word "brother" in english has a  
specialised meaning without nevertheless ceasing to be a word. Now in  
rdf we can create a fam:brother relationship, and it will just happen  
that if you look at the universe of discourse this fam:brother  
relationship is indeed what we know in english as being transitive.  
owl just
gives us a word for that: owl:transitive

>> But it is linked to the following well known rule:
>> { ?r1 owl:inverseOf ?r2 .
>>    ?a ?r1 ?b .  } => { ?b ?r2 ?a . } .
> Not all all.  There are *no* rules in RDF, nor in OWL.  The above  
> is not
> even legal RDF syntax, nor legal OWL syntax.

There may be no rules in rdf, but that does not stop it from being  
possible to create other
languages that have rules. Rules just are short hands for stating  
patterns of relationships. And these patterns exist whether they can  
be expressed in  a well know way in the language or not.

>  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.
> Not at all.  OWL is a a different logical language from RDF.  It just
> happens that OWL (Full) was designed as a same-syntax extension of RDF
> Schema.

I don't believe that. Where is that written?

>> Henry
> peter

Received on Thursday, 23 March 2006 15:57:50 UTC