Re: Dealing with qualified expressions in DAML

I'm afraid that I have one more question that I would like to pose regarding 
this discussion.  Does this "shared extension" side effect take place when other 
restriction elements are used instead of just "hasClassQ"

For example 

<daml:Class rdf:ID="Rabbit">
  <rdfs:subClassOf>
    <daml:Restriction>
      <daml:onProperty rdf:resource="#Eats"/>
      <daml:toClass rdf:resource="#Vegitables"/>
      <daml:hasValue rdf:resource="#Carrots"/>
    </daml:Restriction>
  </rdfs:subClassOf>
</daml:Class>

Now before you said:
>     It is a logical consequence of the information specified that each of
>     the restrictions thus formed has the same extension.
So does that mean that 
   {things that eat Vegitables}
   has exactly the same elements as 
   {things that eat Carrots}

This would imply that anything that eats vegitables eats carrots, which would 
not be intended.

Or is the "side effect" that the restrictions will have the same extention due 
to the use of the same tags in the restriction repeatedly?  If that were the 
case then this example:

<daml:Class rdf:ID="AnimalLover">
  <rdfs:subClassOf>
    <daml:Restriction>
      <daml:onProperty rdf:resource="#owns"/>
      <daml:hasValue rdf:resource="#Dog"/>
      <daml:hasValue rdf:resource="#Cat"/>
    </daml:Restriction>
  </rdfs:subClassOf>
</daml:Class>

Would logically imply that 
   {things that own Dogs}
   has exactly the same elements as 
   {things that own Cats}
Is that correct?

If you could just clarify this, then I think I would understand how exactly one 
is to standardly use restrictions.  

Thank you,
John



> Date: Wed, 18 Sep 2002 11:06:50 -0400 (EDT)
> To: martin@AI.SRI.COM
> Cc: pacheco@AI.SRI.COM, www-rdf-logic@w3.org
> Subject: Re: Dealing with qualified expressions in DAML
> From: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
> Mime-Version: 1.0
> Content-Transfer-Encoding: 7bit
> 
> From: David Martin <martin@ai.sri.com>
> Subject: Re: Dealing with qualified expressions in DAML
> Date: Wed, 18 Sep 2002 07:59:58 -0700
> 
> [...]
> 
> > > > How does that get to be a legitimate inference?  Intuitively, I can't 
see a shred
> > > > of basis for it.
> > >
> > > It is not a legitimate inference.
> > >
> 
> > Thanks.  I'm relieved that it's not a legitimate inference.  But then I
> > have to admit I still can't make sense of your statement:
> > 
> > (2) "a side effect is to assert that each of the restrictions thus formed
> > has the same extension. ."
> > 
> > Clearly we understand one or more of the words in (2) differently - and I
> > suspect it has to do with "side effect" and "assert".
> 
> How about:
> 
>     It is a logical consequence of the information specified that each of
>     the restrictions thus formed has the same extension.
> 
> > I'm not that concerned to get additional clarification; you've already
> > addressed our questions with respect to our tool building effort.
> > (Again, thanks.)  But if you feel like giving additional clarification, I
> > would suggest that you do one of the following:
> 
> > (a) state in a formal notation some legitimate inference from the
> > CartoonCharacter class definition above, which illustrates your statement
> > (2), but is *not* illustrative of "The extension of the restriction is
> > then the intersection of all of them."
> 
> It is a logical consequence of the information specified that
> 
>      {things with at most 1 elephant in their pocket}
>      has exactly the same elements as 
>      {things with at most 2 elephants in their pocket}
> 
> > (b) explain some practical consequence of (2) - say, for a parser builder
> 
> A parser builder doesn't have to worry, such constructs are syntactically
> legal.  A user interface should prevent users from constructing such
> constructs and should complain bitterly if an ontology with such constructs
> is used.
> 
> > OR
> > 
> > (c) Give a pointer to a paper or other document that explains the idea
> > behind (2). 
> 
> The DAML+OIL model theory, available at
> http://www.daml.org/2001/03/model-theoretic-semantics, provides a formal
> definition of what is going on.  
> 
> > Regards,
> > David Martin
> 
> Peter F. Patel-Schneider
> Bell Labs Research

Received on Thursday, 26 September 2002 15:28:20 UTC