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Re: SEM DESIDERATA: my initial desiderata list

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 15 Mar 2002 12:18:28 -0500
To: las@olin.edu
Cc: www-webont-wg@w3.org
Message-Id: <20020315121828G.pfps@research.bell-labs.com>
From: "Lynn Andrea Stein" <lynn.stein@olin.edu>
Subject: Re: SEM DESIDERATA: my initial desiderata list
Date: Fri, 15 Mar 2002 11:23:00 -0500

> Several questions/clarifications:
> 
> 
> In http://lists.w3.org/Archives/Public/www-webont-wg/2002Mar/0173.html, "Peter
> F. Patel-Schneider" wrote:
> 
> >                 Potential Desiderata for the Web Ontology Language
> 
> I (LAS) include only those potential desiderata on which I have something to
> say/ask.
> 
> > Syntax:
> >
> > 1/ Syntax is (equivalent to) n-triples (i.e., RDF syntax).
> >    All syntax (except, maybe, datatypes) is carried in triples.
> 
> Pretty clearly we will need *some* sort of (unordered) listing/grouping
> construct that is bounded, i.e., defines a list/group containing *exactly* the
> listed/grouped elements.  daml:collection was one attempt to provide such a
> thing.  I don't believe we can avoid having such a thing.  (BTW, I also
> believe that adding such a thing to RDF's semantics may cause problems as it
> essentially introduces negation.  Pat?)

There is nothing to prevent a construct like daml:list, or even owl:set.
   The criterion only says that such a construct has to be carried by a
   collection of n-triples.

> 
> > Semantics:
> >
> > 1/ There is a model-theoretic semantics, compatible with the RDF(S)
> > model-theoretic semantics.
> >    All triples are assertions.
> 
> As we discussed, this is one several of us want to question.  But this is only
> a potential desiderata list....
> 
> >    All URIs denote elements of the domain of discourse.
> 
> This doesn't make them real, of course, but yes, they should denote
> "discussable" things; they are names after all.  (But we have to be careful
> about what it means to talk about unicorns....  forall x. (x a unicorn) -> (!
> exists x)......(or, in pseudo-n3,
> this log:forAll :x. {:x a :unicorn} log:implies {log:not {log:exists :x}}.
> 
> >    All classes are elements of the domain of discourse.
> 
> I'm not sure what this means.  Does this mean all classes mentioned?  All
> classes conceivable?  All classes describable (in some language)?  The class
> of all classes that do not include themselves as members?  I'm not trying to
> be difficult, just clear that we're on the same page.

This is agnostic as to which classes have to exist.  However, any
class that does exist must be an element of the domain of discourse, just
like any other entity in RDF.

> >    All properties are elements of the domain of discourse.
> 
> Ditto
> 
> > 2/ Inference is standard entailment in the model theory.
> 
> Not, for example, intuitionistic entailment (cf.
> http://plato.stanford.edu/entries/logic-intuitionistic/ or
> http://www.xrefer.com/entry/552450)?

Standard entailment is the relationship between two formulae defined as
follows:
	F1 entails F2 iff all models of F1 are also models of F2.

Intuitionistic entailment could be defined in the same way, just with a
different notion of model, which would probably break the ``compatible with
the RDF(S) model-theoretic semantics''.

> > Classes:
> >
> > 1/ A way to create / query complex properties is via a defined class, e.g.,
> >    the intersection of a and b, the union of a and b, objects who have at
> >    least one child.
> 
> I am not sure that this use of "defined classes" is the same as what I thought
> DLs meant by defined classes.  Could you clarify?

Well, I'm trying to use something close to DAML+OIL terminology, and not
necessarily close to DL terminology.  In DL terminology ``defined class''
would translate to ``description''.

> > I'm willing to keep this list up to date and to incorporate other
> > desiderata into the list.
> 
> Thanks!
> 
> Lynn Andrea Stein

I've added the above commentary to the desiderata.  I'll sent the revised
document out when any flurry of messages dies down.

I'm also going to add a ``No Solipsism'' item.  :-)

peter
Received on Friday, 15 March 2002 12:40:05 GMT

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