W3C home > Mailing lists > Public > www-rdf-interest@w3.org > December 2004

Re: facts about web ontology languages

From: Charles McCathieNevile <charles@w3.org>
Date: Sat, 11 Dec 2004 08:31:39 -0500 (EST)
To: Frank Clar <Frank_Clar@web.de>
Cc: www-rdf-interest@w3.org
Message-ID: <Pine.LNX.4.55.0412110823440.12980@homer.w3.org>

Warning: My answers are not definitive - I am not one of W3C's big experts on
logic and OWL, and I know very little about DAML+OIL. I hope someone follows
up with more detailed responses to the things I couldn't help with.

On Sat, 11 Dec 2004, Frank Clar wrote:

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

This is what the OWL specifications say, as I understand them. (I think it is
in the owl guide).

>Do DAML+OIL and OWL DL support Description logics and for this reason as
>well first order predicate logic?

I don't know.

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

I don't understand the question. I suspect I don't know the annswer though.

>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.

RDF supports any syntax capable of describing the model. Perhaps a more
interesting question is what kinds of syntax support RDF? There are a number.

I have not done a lot of work reading up on UML, but it seems that there are
ways of mapping a lot of things to UML. I am not sure if they can be
completely mapped both ways.

>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?
>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.

OWL, because it is expressed in RDF (and for interoperability in the RDF/XML
syntax) doesn't need to support reification itself, since it is already part
of RDF.

>Could you declare a default value for a literal, if no value was
>assigned to this property?

I don't think so.

Hope this was some help. Note that I am not W3C's expert on many of these
questions - I am just someone who tries to answer things. I trust that people
who are more familiar with the logic stuff will answer the more  detailed



Charles McCathieNevile             http://www.w3.org/People/Charles
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Received on Saturday, 11 December 2004 13:31:40 UTC

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