Re: facts about web ontology languages

Hi,
just some quick notes. Disclaimer: that's the answers as I understand it right now, I may be wrong. And it's weekend, so my brain is running on half voltage on this, and I've just seen the special edition of LOTR:RotK, so be careful with the answers ;)

> Are they completely decidable?

Yes, OWL DL and Lite are decidable.

> Is it right that only OWL full and RDF/s are not decidable, because they
> do not seperate between concepts and instances?

OWL Full and RDFS are not decidable, and yes, this is a reason.
RDF itself is just a data model, and thus the question does not apply.
 
> Do DAML+OIL and OWL DL support Description logics and for this reason as
> well first order predicate logic? 

DAML+OIL and OWL DL entailment is reducable to Description Logics satisfiability (there's a paper of Ian Horrocks and Peter Patel-Schneider on that, search the web for it). This actually means, they were designed with DL in mind, but there are many flavours of DL, so that question is not easily answered.

DAML+OIL and OWL DL are a subset of First Order Logic (actually, DL is, but because of the above said you may infer this sentence ;)

 
> And do they support first respectively second order predicate logic?

You can't express everything in DL that you can express in FOL (and much less SOL).

> Only DAML+OIL and OWL lite and DL support first order predicate logic,
> because they are based on Description logics?  

First Order Logic  is more expressible than DL. But it's undecidable.
 
> What different kinds of syntax do the above named languages support and
> is it possible to map all of them to UML? 
> RDF/XML, abstract syntax, n3, n-triples...I have just found several
> articles, which describe methods to map RDF/S to UML. 

Many. And you can think of even more. But they -should- be interchangeable.
RDF/XML though is the official one, also the definition of OWL DL happens on the Abstract Syntax (as RDF/XML is far from easy human readable).

About mapping to UML, well, several approaches. Read the articles :)

> Is it possible to express a kind of class variable, which has one single
> value for a concept? Is there a way to define one indirectly?  

I don't understand, sorry.
 
> Do DAML+OIL and OWL support reification and do they offer the possiblity
> to add additional information to the statements? I guess that
> reification has no meaning in OWL and DAML+OIL. 

Well, OWL Full semantics completely entail the RDF semantics, so there is reification.
 
> Could you declare a default value for a literal, if no value was
> assigned to this property?

This would hurt the Open World Assumption, and thus, no, you can't.

More questions than I thought - hope it helps a bit!

denny

Received on Saturday, 11 December 2004 19:49:27 UTC