Re: Dealing with qualified expressions in DAML

From: John Pacheco <pacheco@AI.SRI.COM>
Subject: Re: Dealing with qualified expressions in DAML
Date: Thu, 26 Sep 2002 13:55:17 -0700 (PDT)

> 
> > Date: Thu, 26 Sep 2002 15:53:24 -0400 (EDT)
> > Subject: Re: Dealing with qualified expressions in DAML
> > From: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
> > 
> > > 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}
> > 
> > Yes, except that that is not what the syntax above says.  To get this you
> > need two toClass pieces.
> 
> So then does the above syntax just define the class
> 	{things that only eat vegitables} intersect
> 	{things that eat a carrot}
> without specifying this "is the same class as" side effect?

It also has the ``same class as'' side effect.

> Just to be sure I understand your meaning, the "sub-restrictions" having the 
> same extention occurs whenever a particular tag in the <Restriction>
> occurs more than once.  Is that right? 

Every restriction with extra components has this ``is the same as'' side
effect.  It occurs with two toClass, a toClass and a hasValue, two
onProperty, etc., etc.  If there are two toClass and two onProperty, then
you get the ``same class as'' between all four combinations.


> Thanks,
> John

peter

Received on Thursday, 26 September 2002 17:10:11 UTC