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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 06:32:09 -0400 (EDT)
Message-Id: <20020924.063209.28099437.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: Mon, 23 Sep 2002 22:18:39 -0500

> Rather than respond point by point, let me try to see if I can 
> summarize what seem to be the main clashes of intuition here.
> My view of the range of a property is that it is a particular class 
> which as far as possible defines the, well, range that the values of 
> the property can take. Of course, there is no guarantee that any 
> property will as it were 'fill up' its range, so it can make sense to 
> apply conjunctive semantics to multiple range assertions; but the 
> range is a definite thing associated with the property; it is part of 
> the very specification of the property; knowing the range is knowing 
> something particular about the property, a key piece of information. 
> It allows one, for example, to detect inappropriate uses of the 
> property under some circumstances. Ranges can be used to convey 
> information relevant to a property, for example by having an 
> associated datatype.

OK, this is your view.

> Your view, as I understand it, is that a range is simply any class 
> which all the values are in. In particular, the idea of there being 
> *a* range is silly, on this view: all properties will have multiple 
> ranges. 

OK, this is my view.

> What I am calling 'the' range, on this view, is something 
> like the smallest range; 

Well, if this is your view, then you have to allow inference to determine
'the' range, because even RDFS allows multiple ranges.

What is 'the' range of foo in

	foo rdfs:range bar .
	foo rdfs:range baz .

> but supersets of this can also be called 
> ranges. I can see that with this view, the proposed semantics  and 
> Jeremy's entailment are both quite natural. But what worries me about 
> this view is that it seems to discount the most useful aspects of the 
> 'range' idea.
> The first view seems to go naturally with an intensional view of 
> classes as real things that can have properties, while the second is 
> more natural if one thinks of classes simply as sets in extension. 
> Maybe the different directions our intuitions go in reflect a 
> basically different world-view about the nature of classes.

Well, I think that it is your view that has technical problems, as
evidenced by the property foo.

> However, I would like to return to a more technical debate. You claim 
> the several intuitive entailments go through on your semantics but 
> not on mine. Seems to me that this isn't correct, so far: the correct 
> form of Jeremy's entailment and the intersection example both work on 
> both semantics. 

Your interpretation of Jeremy's natural-language paraphrase of his example,
that is.  I prefer to go by the formal version of Jeremy's example.

> So just on grounds of interoperability, it seems to 
> me that the burden of proof is on you to show why OWL needs to change 

Well, precisely because of the above example.  I believe that an
intersection of bar and baz is a range of foo.  If you believe in 'the'
range, then what else can it be for foo?  

Perhaps you would like to annoint this most-restrictive range as the range.
However, this won't work, as there is no unique most-restrictive range in
OWL, nor, in general, in RDFS.

So, from purely technical reasons, there is no single range possible for
either RDFS or OWL properties, and even determining a most-restrictive
range requires inference.

> Pat

Received on Tuesday, 24 September 2002 06:32:15 UTC

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