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Re: RDF MT: Default values for rdfs:domain and rdfs:range?

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Thu, 28 Mar 2002 14:14:42 +0000
Message-Id: <5.1.0.14.0.20020328140429.00abc5e0@0-mail-1.hpl.hp.com>
To: Jeen Broekstra <jeen.broekstra@aidministrator.nl>, www-rdf-comments@w3.org
Hi Jeen,

Pat Hayes normally deals with MT questions, but he is only intermittently 
around at the moment, so I'll risk a comment.

At 14:27 28/03/2002 +0100, Jeen Broekstra wrote:


>I am rather confused as to what exactly the domain/range of a
>property should default to if no explicit domain/range is
>specified,

I don't think there is any notion of default.  In the absence of 
domain/range constraints, then no constraints on the domain and range are 
specified.

Do you have a requirement for such defaults?

>  and I was hoping your insights could clear it up for
>me. I realize that the debate over what exactly constitutes a
>resource and what a literal is far from over, but nevertheless I
>hope that this practical issue can be resolved.
>
>In the case of rdfs:domain, it is relatively straightforward to
>assume that if the domain is not specified, it is in fact
>rdfs:Resource.

Hmmm, it may be straightforward, but it is also potentially risky.  What if 
RDF were extended to allow literals as subjects.

>  In the case of range the issue becomes cloudier
>though, since legal values for objects include literals.
>According to the RDF MT we should not confuse between literals
>and their denotation, which I take to mean that literals can
>conceivably be denoted by URIs. Furthermore, we assume that the
>population of the class rdfs:Resource consists of anything that
>could be denoted by a URI.

I think we have been deliberately vague about the relationship between 
literals and resources.  We have some charter contraints that stop us 
getting into this fully.  So we are leaving things as free as possible for 
a future WG.  You might think of this as some deliberate underspecification.


>This leads me to think that the range of a property also defaults
>to rdfs:Resource, and that any use of that property with a
>literal value is within that range. Is this correct?

You may care to assume that.  I couldn't possibly comment.

Sorry, English joke.  I won't say whether you are correct or not.  I will 
say that RDF(S) makes no such statement.

Brian
Received on Thursday, 28 March 2002 09:16:35 GMT

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