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Re: DAML+OIL (March 2001) released

From: Dan Connolly <connolly@w3.org>
Date: Tue, 10 Apr 2001 10:54:31 -0500
Message-ID: <3AD32CB7.652D4BD5@w3.org>
To: "Hart, Lewis" <lhart@grci.com>
CC: www-rdf-logic@w3.org
"Hart, Lewis" wrote:
> 
> I have some rather pedestrian, non-theoretical questions about the latest
> DAML+OIL specification. The specification page directs comments to this
> list,

yes...

> but the typical list topics have been far removed from these types of
> issues.

Unfortunately so.

> But if this is not the forum to address them, then where should they
> be addressed?

This is the forum to address them.


> Some examples of questions I have are:
> 
> Consider this partial definition from the latest spec...
> 
> <rdf:Property rdf:ID="unionOf">
>   ... omitted ...
>   <rdfs:domain rdf:resource="#Class"/>
>   <rdfs:range rdf:resource="#List"/>
> </rdf:Property>
> 
> Why is it not defined like this:
> 
> <ObjectProperty rdf:ID="unionOf">
>   ... omitted ...
>   <domain rdf:resource="#Class"/>
>   <range rdf:resource="#List"/>
> </ObjectProperty>

I'm not sure; I suspect it's a bug/oversight.

> Specifically,
> 
> 1. The semantics of rdfs:domain, which are "believed to be flawed" [1],  are
> different that the semantics of daml:domain. So, why is rdfs:domain used?
> Would it not, in general,  be preferred to use daml:domain in the DAML+OIL
> specification?

I suppose we estimated that it's more cost-effective to
get the flawed semantics of rdfs:domain fixed than to
manage a new property.

> 2. The property daml:unionOf is of type rdf:Property, but has domain and
> range of daml:Class and daml:List. How should a RDF (but not DAML) aware
> agent deal with that?

Er... in the usual way; that is: by inferring daml:Class
as a type of any subjects of statements whose predicate is
daml:unionOf, and by inferring daml:List as a type
of any objects of such statements.

> Or, stated another way, if we are trying to allow some
> usability of DAML by RDF/RDFS only applications, this doesn't seem to
> support that.

How so?

If you mean that we haven't expressed daml:unionOf in
terms of RDFS, then yes, that's the case, we have not.
That seems impossible to do, no?

> 3. This is a property which relates objects to other objects, wouldn't the
> daml:unionOf be better defined as a daml:ObjectProperty?

Probably; I'm not sure about the details of ObjectProperty vs.
DatatypeProperty, so I hope somebody else follows up...

> 
> Thanks. - Lewis
> 
> [1] http://www.daml.org/2001/03/reference.html#domain-def
> 

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 10 April 2001 11:54:40 GMT

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