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Re: rdf inclusions (was Re: DAML Level of Effort for FY03-FY05)

From: Frank Manola <fmanola@mitre.org>
Date: Mon, 22 Apr 2002 09:19:21 -0400
Message-ID: <3CC40DD9.9050803@mitre.org>
To: Drew McDermott <drew.mcdermott@yale.edu>
CC: www-rdf-logic@w3.org
Drew McDermott wrote:

>    Drew McDermott writes:
>    > Anyway, the following strikes me as the only reasonable point of view:
>    > There is simply no way to import part of an ontology, as Sandro and
>    > Frank both seem to want to do. 
>    [Sandro]
>    I'm not sure how I was misunderstood.  I think the only reasonable
>    thing to import is another RDF graph (serialized as some
>    web-accessible document and named by the web address).
> Hey, I can misunderstand anyone.  I was probably accepting something
> Frank implied.

Well, maybe!  Just to clarify (?), I was suggesting "yes" as an answer to:

 >   Does using a term defined by some ontology O in some
 >   RDF graph G mean that G is using O?

meaning that G is "using" O if it "uses" some piece of O (the term in 
question).  However, I think I'm agreeing with (both of?) you in wanting 
to distinguish that situation (picking and choosing) from G "using" (or 
importing) O in the sense of committing to the entire ontology.

>    [Sandro]
>    So are you committing to some particular web content being served at
>    the namespace address?  That's a difficult issue to get consensus on.
>    People want to be able to use XML instance data with schemas not on
>    the web and not necessarily shared.  That seems to me like a bad idea
>    with ontologies, but it's a big problem any XML-namespaces proposal
>    will run into.
> Unless I'm misunderstanding again, I think we're on the same
> wavelength here.  There should be a difference between grabbing XML
> instance data on an ad hoc basis, and saying, I'm committing to the
> claims of yonder ontology.

Exactly.  But I also think (just to nail this down further) that there 
should be a difference between grabbing (or referring to by their URIs) 
RDF or DAML facts (instances) or definitions of terms (which is clearly 
possible) and committing to *all* the claims of yonder ontology.

>    [me]
>    [example of typical RDF using stuff without importing it]
>    > But how can a computer see all this?  Should it just assume that any
>    > namespace that expands out to something ending in ".daml" somehow is
>    > an ontology?  This strikes me as a silly tactic for avoiding an
>    > "imports" declaration.
>    [Sandro]
>    Is it important to you to keep the instance data and the ontology in
>    separate graphs?  I think the Semantic Web is based on merging all the
>    graphs one believes and can access, so the instances and their
>    ontologies should not be considered separable graphs.
> No, the graphs aren't separate.  But some subgraphs are more equal
> than others.  For instance, suppose I write a DAML type checker.
> Given some instance data, and the ontologies they use, I should be able
> to check that the data don't contradict the ontology.  (E.g., no one
> has two mothers if the ontology says they shouldn't.)  Now suppose I
> suck in some instance data, and there happen to be some daml
> assertions mixed in.  It seems to me that without an explict "imports"
> statement I would be justified in just taking the instance data that I
> wanted (say, with a particular syntactic form) and ignoring the
> extraneous daml assertions.
> Hmmm.  I seem to contradict myself, given that I want to forbid
> picking and choosing pieces of an ontology, but allow exactly that in
> other cases.  The resolution is that ontology importing seems to be a
> distinguished case, which should have a clear syntactic tag.  I
> understand what it means to import an ontology: take it all.  I am
> willing to allow for all sorts of other ad hoc cases, but we don't
> have to legislate those up front.  
>                                              -- Drew McDermott

Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Monday, 22 April 2002 09:08:47 UTC

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