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Re: Summary and some analysis: New Semantics Initiative

From: Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
Date: Wed, 12 Jun 2002 23:20:15 +0200
To: "Brian McBride <bwm" <bwm@hplb.hpl.hp.com>
Cc: "rdf core <w3c-rdfcore-wg" <w3c-rdfcore-wg@w3.org>
Message-ID: <OF6029AC14.6A9A38EA-ONC1256BD6.0075114D@agfa.be>



Brian,

> Here is my summary of the new semantics initiative as I understand it so
far:
>
> There are two separable issues being discussed under this title:
>
>    o using a melange of model theories to define the semantics of SW
> languages isn't going to work, as demonstrated by webont
>
>    o a mechanism for darkening some triples in a non-monotonic way.
>
> I muddied the waters by introducing the second into this thread.  That
was
> a mistake.  This summary is just about the first issue.
>
> It is proposed to produce a W3C note which outlines a strategy for
defining
> the semantics of SW languages in terms of Lbase, a representation of
FOL.
>
> A new deliverable by RDFCore WG is proposed.  This will define the
> semantics of RDF in terms of Lbase.  It is proposed that this document
is
> in addition to the model theory document and will define exactly
equivalent
> semantics to the model theory.
>
> This proposal is motivated by a concern that:
>
>    o model theory is hard:  it will take a lot (more than available) of
> expert effort for each SW language to define its semantics as a model
theory
>
>    o it is not clear how the model theories of multiple SW languages can
be
> combined to provide a clear semantics for mixed language documents
>
> The proposed new document is expected to have minimal effects on the
> content of the RDF/XML syntax doc, the primer, the RDF schema doc and
the
> test cases doc and only minor effects on the model theory doc.

that's what I believe too

> It is suggested that it is important to include this new deliverable in
the
> current round of deliverables by RDFCore so that it has normative status
> enabling other WG's (webont?) to build on it. [I'm not sure about this
one
> - see below]
>
> It is suggested that this new form of representing the semantics will be
> easier for folks to understand.
>
> Jos has tested the new proposal in Euler and found no bugs.

well, we started testing and found no (MT) bugs so far
we actually test and experiment in N3 and we use
for example n-ary relational statements like
  { } :R ( :t1 :t2 ... :tn ) .
and n-ary functional statements like
  :t0 :f ( :t1 :t2 ... :tn ) .
whereby
  { } is the empty graph (which is true)
  ( ... :ti ... ) is a rdf:List (not owl:List)
  :t0 is a function value (which could be a blank node)

> It is suggested that this is a harmless change; if it isn't adopted by
say
> webont, it will still do some good and no harm.

I believe it is proposable/reasonable in webont

> I have spoken to some of the webont folks here, (Horrocks, PFPS, van
> Harmlen) and got a mixed response.  One criticism is timing; a concern
that
> layering is a deep and hard issue that needs careful consideration, not
> rushing in at the last minute.
>
> I assume that the proposed new document is not normative as it is based
on
> Lbase which is defined in a note.  Is this a problem?  At least it ducks
> the question of which is right if the axiomatic and model theory
semantics
> disagree.

why not partly in a revised MT document (with appropriate references)?

> I have a number of process concerns about this, in particular I would
like
> to ensure that the whole community expert in this issue is involved
working
> it out, but that doesn't sound like a good thing to do to RDFCore right
now.

and still, it should be possible, no?

-- .
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Wednesday, 12 June 2002 17:20:55 EDT

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