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Re: DAML/RDF: a semantics and 2 more syntaxes

From: Dan Connolly <connolly@w3.org>
Date: Sat, 14 Oct 2000 09:34:28 -0500
Message-ID: <39E86EF4.36E1E612@w3.org>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
CC: www-rdf-logic@w3.org
"Peter F. Patel-Schneider" wrote:
[...]
> > In particular, I regard daml:equivalentTo as
> > having the same semantics as (= X Y) in KIF.
> > i.e.
> >
> >   (defrelation http://www.daml.org/2000/10/daml-ont#equivalentTo (?x ?y)
> >       := (= ?x ?y) )
> 
> OK, this is a potential specification of the meaning of equivalentTo via
> translation into some second-order logic.  Under this specification,
> it appears that equivalentTo would allow making equivalences between
> unrelated logical statements.

OK... so it's this level that you're after. I'll try to
cook up a KIF (or perhaps larch) specification for
what I think the rest of the DAML vocabulary means. Note 
that this will just be my view of DAML, and I don't expect
it to become part of the DAML spec until, for example,
a bunch of folks have had a chance to compare it with the OIL
denotational semantics.

For the DAML terms that are said to be equivalentTo
some RDFS term (e.g. Class, subClassOf, subPropertyOf, etc.)
you might find this specification of the RDFS terms
relevant:


    Semantics of RDF Standard Terms
    in progress Aug 2000 
	http://www.w3.org/2000/07/hs78/rdf-ms
	$Revision: 1.15 $ of $Date: 2000/08/13 04:37:44 $

e.g.

 [[[
 domain: Property -> Class 

 [...]

    type(_v_, _c_) 
        if 
            _s_(_f_, _v_) 
            domain(_s_, _c_) 
 ]]]

Oh... and some of the work we did on DAML before
we yanked the formal specification of each term out
is still available:

	DAML Scribblings
	http://www.w3.org/2000/07/DAML-stuff
	Fri, 11 Aug 2000 18:41:14 GMT

e.g.

[[[[
Unambiguous 

        aka Injective, or 1-1. Compary max-cardinality=1.

        isEquivalentTo(x,z) 
                type(p, Unambiguous) 
                p(x, y) 
                p(z, y) 
        Unique 

        aka functional

        isEquivalentTo(y, z) 
                type(p, Unique) 
                p(x, y) 
                p(x, z) 

]]]]

> 
> However, the translation from daml into kif provided in the attachments to
> your message doesn't carry this at all.

Right... the semantics of daml:equivalentTo aren't
expressed in the DAML ontology, and the attachment
was just a transliteration.

>  In fact, I don't see ANY semantics
> being provided by this translation (and I'm not sure that is was supposed
> to, by the way).  However, if it was intended that the translation into KIF
> syntax was not intended to provide some help for semantics, then I don't
> know what it was intended to be.

OK... so I didn't succeed in making the point I was trying
to make, which was that the grouping of RDF assertions
into XML elements doesn't matter; it dissapears during
RDF parsing. Note that the grouping of assertions
in the <Class ID="TallPerson"> element went away
in the daml-ex.kif.


> > The recent suggestion[026] that defined classes can be
> > expressed without quoting/reification seems to
> > suggest that DAML consumers be allowed to
> > rely on information from the XML serialization about
> > which properties were stated where. If you
> > want to use RDF APIs and tools, that won't work.
> > This information disappears when an RDF document is
> > parsed into a graph.
> 
> I don't see this at all.

I hope to explain it to your satisfaction eventually,
but I think this turns out to be somewhat tangential
to what you really want at this point:

> Again, let me reiterate my plea.  What I want is some clear idea of what
> the meaning of the DAML-ONT constructs are.  I don't care too much about
> how this meaning is conveyed, except that it be clear.  (Of course, I do
> happen to think that some methods for conveying meaning are better than
> others.)  To go along with the meaning, I would also like to see what
> restrictions are placed on the constructs (see the ongoing discussion of
> the difference between these two with respect to equivalentTo).
> 
> Peter Patel-Schneider

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Received on Saturday, 14 October 2000 10:34:31 GMT

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