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Re: Web Ontology Requirements Document - comments sought

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Mon, 25 Mar 2002 10:21:50 -0500
Message-ID: <3C9F408E.DDC5C468@cse.lehigh.edu>
To: Graham Klyne <GK@ninebynine.org>
CC: public-webont-comments@w3.org

Thank you for your comments. As for use cases, we did not try to provide
an exhaustive set, we only wanted to find very distinct, representative
use cases. The use case you mention is a good one, but unless it
generates some new requirements, there is no real need to add it to the

I want to clarify that the objectives section of the document lists
things that some members of the group thought would be useful, but there
was no consensus on. Sometimes this was because the objective was not
well-defined, other times it was because it was considered too hard for
the first version of the language. There was no effort to keep these
objectives orthoganal, and thus some may overlap with each other (as you
point out, procedural attachments could be used to perform arithmetic or
string comparisons). Your concerns about procedural attachments are duly
noted, and should be mentioned in the description of the objective. It
is highly unlikely that this objective will be addressed in this version
of the language, but if it is, we'll take your suggestions into


Graham Klyne wrote:
> All,
> I have a possible additional use case for you:  content negotiation.
> Some time ago, I did some work for an IETF specification using logical
> expressions to describe sets of features, in a fashion having similarities
> with Description Logics.  In particular, the feature matching (i.e.
> matching content origination capabilities with receiver capabilities) was,
> I think, a form of subsumption calculation.  See RFC 2533 [1] for more details.
> Now we have CC/PP using RDF to describe client capabilities, but without
> any framework for matching them with origination capabilities.  E.g. the
> sort of missing capability one could imagine is a number of content
> generation stylesheets, each associated with a description of required
> media features, from which a selection could be made by matching with the
> client CC/PP profile.  Preferably, this stylesheet would have a form very
> similar to the CC/PP profile.  This could provide a basis for protocol- and
> application-independent content negotiation [2].
> A long-term goal of mine is to work to converge the CC/PP and IETF RFC2533
> frameworks to the point that the semantics, if not the syntax, are readily
> exchangeable.  Some work on converging vocabularies is underway.  I had
> been looking to the DAML/OWL work to provide a basis for implementing
> feature matching of descriptions using logical expressions.  There may be
> some difficulties with the RFC 2533 form, as it uses negation and
> disjunction, and keeps the computation tractable by limiting the
> expressions in other ways.  (I don't fully grok the constraints on DL
> expressions that are used to ensure tractability.)
> ...
> I have one other comment on the requirements document, concerning
> procedural attachments.
> While I can understand that there will be new applications that will need
> some kind of extension to OWL to fulfill their requirements, I think it
> would be a great shame if the language cannot satisfy its original use-case
> goals without such extension (particularly given that string and arithmetic
> primitives are also noted in the objectives).
> Also, the term "procedural" makes me nervous.  I strongly feel that such
> attachments, where used, should not be used to allow an OWL expression to
> have side-effects, as that would introduce all sorts of
> evaluation-scheduling constraints (e.g. would effectively prohibit caching
> of already-evaluated results).  Related to this, I think that where
> external evaluations are used, the OWL processor should be able to know if
> they depend upon volatile conditions -- i.e. can the result be evaluated
> once and then cached for use as-needed?  (Specifically, I would like to be
> able to perform OWL evaluations in the framework of a functional
> programming environment using lazy evaluation.)
> #g
> --
> [1] ftp://ftp.rfc-editor.org/in-notes/rfc2533.txt
> [2] ftp://ftp.rfc-editor.org/in-notes/rfc2703.txt
> At 11:28 PM 3/19/02 -0500, Jim Hendler wrote:
> >RDFers - the Web Ontology Working Group has published our first working
> >draft - a use cases and requirements document for the Web Ontology
> >Language [1]. We are soliciting comments on the document at
> >mailto:public-webont-comments@w3.org and general discussion of these
> >issues on rdf-logic.   We'd very much like to hear from you
> >  thanks
> >  Jim Hendler and Guus Schreiber
> >  WebOnt WG CoChairs
> >p.s. apologies for the cross post - we thought both groups might be
> >interested.  Please direct responses as discussed above.
> >
> >[1] http://www.w3.org/TR/2002/WD-webont-req-20020307/
> >
> >
> >
> >--
> >Professor James Hendler                           hendler@cs.umd.edu
> >Director, Semantic Web and Agent Technologies     301-405-2696
> >Maryland Information and Network Dynamics Lab.    301-405-6707 (Fax)
> >AV Williams Building, Univ of Maryland            College Park, MD 20742
> >http://www.cs.umd.edu/users/hendler
> -------------------
> Graham Klyne
> <GK@NineByNine.org>
Received on Monday, 25 March 2002 10:40:07 UTC

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