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Re: possible semantic bugs concerning domain and range

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Tue, 24 Sep 2002 22:22:55 -0400 (EDT)
Message-Id: <20020924.222255.09116718.pfps@research.bell-labs.com>
To: phayes@ai.uwf.edu
Cc: www-webont-wg@w3.org

From: pat hayes <phayes@ai.uwf.edu>
Subject: Re: possible semantic bugs concerning domain and range
Date: Tue, 24 Sep 2002 18:09:38 -0500

[...]

> Yes, that is a good point, I confess, and one that forces me to admit 
> that the idea of 'the' (singular) range has to be relaxed.  But even 
> in this case I would prefer to say that both bar and baz are ranges, 
> and that it therefore follows that any value of foo is in their 
> intersection, but not that the intersection *was* a range.
> 
> I want to be able to restrict the class of range classes to a limited 
> set in a particular application (eg they might correspond to Java 
> classes, or have associated datatypes). On my view, being a range is 
> (or at any rate, can be) a more substantial claim than merely being a 
> class which holds all the values. Maybe we could have two notions of 
> range: your purely extensional one, and the RDFS intensional one. 
> But it seems to me that we don't really need to be able to transmit 
> rangeness up the subclass hierarchy, since for you the only 
> significance of being a range is that it contains all the values: and 
> if you say that explicitly using rdf:type, it holds in both semantics.
> 
> Heres a way to phrase the difference: call a class a protorange iff 
> it contains all the values of a property. For you, protoranges are 
> ranges. For me, only some of the protoranges need be ranges. Clearly, 
> iff semantics is appropriate for protoranges; but many applications 
> of the notion of range require us to be able to identify particular 
> protoranges as the ones to which other information is associated, 

I would like to know about these applications.  In particular, I would like
to know about these applications that actually work correctly in the
presence of super-properties with different ranges.

> and 
> if we make the identification then this ability to distinguish 
> particular protoranges is lost (or requires extra machinery). Whereas 
> it seems to me that applying the iff semantics provides no useful 
> extra entailments. It allows one to conclude that many more classes 
> are ranges, of course, but all this does is make manifest that the 
> notion of 'range' has been (from my point of view) fatally weakened. 

Please present some indication of how the iff definition of range fatally
weakens the notion of `range'.

> These can all be expressed using my notion of range and 
> rdfs:subClassOf or rdf:type. The important inferences about ranges - 
> notably, the kind that arise from an association of a datatype with a 
> range - apply in both semantics, but require more care to state in 
> yours.  

Do these inferences actually work?  I thought that RDF Core had decided
that they didn't work in the presence of super-properties.

[...]

> Pat

peter
Received on Tuesday, 24 September 2002 22:23:06 GMT

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