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Re: need to determine what RDF is

From: Dan Brickley <danbri@w3.org>
Date: Thu, 30 May 2002 09:15:49 -0400 (EDT)
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
cc: <www-rdf-comments@w3.org>, <em@w3.org>, <w3c-semweb-cg@w3.org>
Message-ID: <Pine.LNX.4.30.0205300909190.26121-100000@tux.w3.org>

+cc: SemWeb CG, Eric Miller

Thanks Peter. I think you're right that there is an issue here w.r.t.
clear use of terminology. W3C has work to do in being more
explicit about what is meant by the phrase "Resource Description
Framework", and in explaining how that relates to the currently chartered
work items of RDF Core, of WebOnt, and of as-yet-unchartered efforts
(hypothetically RDF rules and/or query, for eg.).

Some of this clarification is also work that we might expect RDF Core to
address, of course. I'm copying Eric and SW CG as my own belief is that
there's a broader-than-RDFCore issue here. It is more technical than most
issues SW CG address, yet at base mostly terminological in nature. We need
a plan for making progress on it.

I'd like to hear from Eric and Brian w.r.t. whether they'd prefer RDF Core
or SW CG to take a first crack at this. Having it lodged in the RDF Issue
List seems worthwhile, regardless.



On Thu, 30 May 2002, Peter F. Patel-Schneider wrote:

> [This is a repackaged version of part of a mail message that I previously
> sent, with new text explicitly bringing forward the important points that I
> feel need to be addressed by the W3C RDFCore Working Group.]
> There is currently a debate on just what the Resource Description Framework
> (RDF) is.  The fuel fanning this debate is partly an implicit definition of
> the Resource Description Framework held by some people and partly
> deficiencies and vaguenesses in the RDF documents, even the new Working
> Drafts.  Ordinarily it would not be the job of the W3C RDFCore Working
> Group to consider the former portion of this fuel, but the people holding
> it include prominent members of the W3C RDFCore Working Group, which, I
> believe means that the W3C RDFCore Working Group has an urgent task to
> clarify the RDF documents to either support or explicitly deny this
> implicit definition of the RDF.
> As this definition is implicit, I would have severe difficulties in
> describing it.  Moreover, as what I have learned of this implicit
> definition is completely counter to what I believe the RDF has to be, I
> would have even more difficulties in giving an evenhanded description of
> the implicit definition.
> However, I can propose a definition of RDF(S) (RDF(S) is used here as a
> shorthand for ``RDF or RDF Schema, respectively'') that I feel is
> completely counter to this implicit definition.  My definition is that
> RDF(S) is what is defined in the RDF(S) documents, whatever they end up
> being, and nothing more.
> So, an agent (a piece of software, a system, a person, ...) that is
> determining entailments, or performing deductions, or making inferences, or
> drawing conclusions, can label these entailments, or deductions, or
> inferences, or conclusions as being RDF(S) only if they are indeed RDF(S)
> entailments, as defined in the RDF Model Theory document.  An agent can be
> correctly described to be determining RDF(S) entailment (or performing
> RDF(S) deductions, or making RDF(S) inferences, or drawing RDF(S)
> conclusions, or doing RDF(S), or ...) only if its behaviour can be viewed
> as determining (or generating) correct (i.e., both sound and complete)
> RDF(S) entailments as defined in the RDF Model Theory document.
> This definition of RDF(S) means that an agent that takes into account
> meanings that are not expressible in RDF(S) or not expressed in RDF(S) and
> uses these meanings in determining entailment is not performing RDF(S)
> entailment.  If the W3C RDFCore Working Group decides that accept this
> definition of RDF(S), then I feel that it should modify the wording
> associated with rdfs:comment (and similar wording) to indicate that
> information not expressed in RDF documents is not part of RDF.
> I give several examples to show some consequences of this definition.
> The examples use the n-triples notation, with the common addition of QNames
> as abbreviations for URI references.
> Suppose an agent is given
>   <ex:Student> <rdfs:subClassOf> <ex:Person> .
>   <ex:John> <rdf:type> <ex:Student> .
>   <rdfs:subClassOf> <rdf:type> <rdf:Property> .
>   <rdfs:subClassOf> <rdfs:domain> <rdfs:Class> .
>   <rdfs:subClassOf> <rdfs:range> <rdfs:Class> .
>   <rdfs:Class> <rdf:type> <rdfs:Class> .
> and responds that it entails
>   <ex:John> <rdf:type> <ex:Person> .
> This agent is not an RDF reasoner (is not doing RDF).  Its reasoning is
> unsound in RDF.  The agent may be an RDFS reasoner, but it is not doing
> RDF.
> Suppose that an agent is given
>   <ex:best-friend> <rdf:type> <daml:UniqueProperty> .
>   <ex:age> <rdf:type> <daml:UniqueProperty> .
>   <ex:bob> <ex:best-friend> <ex:margaret> .
>   <ex:bob> <ex:best-friend> <ex:peggy> .
>   <ex:peggy> <ex:age> "35" .
>   <ex:margaret> <ex:best-friend> <ex:susan> .
>   <ex:margaret> <ex:best-friend> <ex:jane> .
>   <ex:susan> <ex:age> "43" .
>   <ex:jane> <ex:age> "55" .
>   <daml:UniqueProperty> <rdfs:label> "UniqueProperty" .
>   <daml:UniqueProperty> <rdfs:comment> "compare with maxCardinality=1, e.g., ..." .
>   <daml:UniqueProperty> <rdfs:subClassOf> <rdf:Property> .
> and responds that it entails
>   <ex:margaret> <ex:age> "35" .
> This agent is neither an RDF reasoner nor an RDF Schema reasoner.  Its
> reasoning is unsound in both RDF and RDF Schema.
> Peter F. Patel-Schneider
Received on Thursday, 30 May 2002 09:16:33 UTC

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