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Re: [WSDL] Message Typing

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Fri, 19 Mar 2004 10:02:33 -0500 (EST)
Message-Id: <200403191502.i2JF2Xs5009322@pantheon-po04.its.yale.edu>
To: public-sws-ig@w3.org

David Martin's message of 16 March concerns the problem of a web
service expecting as input an element of some OWL class.  The problem
(I think) is that in reality all a program can receive is a
_description_ of an object, but we would like to abstract from any
particular description and say "Input A must be a Person."

> [David]
> I'm afraid I haven't much time to think through these issues, but 
> intuitively I have the strong feeling that it should be possible to 
> arrive at some reasonably straightforward solution.  What about 
> something along these lines:
> An input type (of a Semantic Web service) is specified as
> 1) the URI of a named OWL class C, along with
> 2) a set of URIs for loadable OWL KBs in which that class is defined.
> (Typically I think there would just be a single KB, but we're allowing 
> for the case in which relevant declarations exist in several KBs.)
> An input corresponding to that type is
> 3) a collection of OWL instances, of which one is identified as the 
> "designated instance" DI.
> Something like the following three conditions would be used to establish 
> the validity of the input:
> Let Knowledge Base K be the union of all the KBs mentioned in (2) along 
> with the instances of (3).
> C1) DI has to be properly classifiable as an instance of the class C, 
> using standard DL classification techniques, in the context of K.
> C2) By special convention, the restrictions in K that apply directly to 
> DI must themselves be "concretely instantiated" in K.  (So, if there's a 
> restriction that an instance of class C must have exactly 1 instance of 
> property P, then exactly 1 such instance of P for DI must be present in K.)
> C3) This special convention must also hold for the other instances in 
> (3), besides DI.  [I list this separately because I'm less clear about 
> it :-].
> I'm not a DL expert, and the above is fuzzy in certain ways, and I've no 
> doubt I'm omitting various details and subtleties of the problem (and 
> I'm looking forward to hearing what they are :-).   I'm hoping to 
> generate some discussion towards a pragmatic set of conventions that 
> might ensure the usefulness of OWL for purposes such as the one at hand.

Am I right, David, that this is an attempt to capture, in DL-ese, what
it means for a set of data to be an adequate description of an object?
Assuming that's correct, then I have two questions:

1. What is the purpose of the collection of OWL instances mentioned in
   "3)" of which DI is an element?

2. When you say "must themselves be 'concretely instantiated' in K,"
   do you mean that the same set of conventions must be recursively
   applied?  That is, if a person has exactly one head, then the
   description of the person must contain a description of a head that
   applies unambiguously only to that person's head?  If so, the
   requirement seems a little extreme, and possibly ill-founded.

Let me make a suggestion that I think others have already made: Why
not stipulate that at the process level we can use Owl classes as
types of inputs, and that the grounding must then spell out exactly
which information the web service requires in order to know which
person is meant?

                                             -- Drew

                                   -- Drew McDermott
                                      Yale Computer Science Department
Received on Friday, 19 March 2004 10:02:38 UTC

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