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Re: WOWG: compliance levels on next teleconf

From: Deborah McGuinness <dlm@KSL.Stanford.EDU>
Date: Wed, 01 May 2002 08:32:52 -0700
Message-ID: <3CD00AA4.2432D090@ksl.stanford.edu>
To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
CC: www-webont-wg@w3.org
sorry - my email got sent before it was completed.

here is the completed email.

I also presented our strategy to the EU/US joint committee meeting readout
yesterday.
I reiterated the goals I stated in the email to webont in
http://lists.w3.org/Archives/Public/www-webont-wg/2002Apr/0362.html
(and also mentioned explicitly the goal of being a step above rdf(s))

One possible strengthened criteria for the design of Level 1 was proposed
- attempt to make level 1 cover the needs of a significant number (50-75%)
of our expected user communities.

I think a restatement of Frank's and my goals is to

* agree on a language that is easy enough and useful enough for tool
builders to support.

easy enough implies:
    a - the language should be small enough to be explainable and
understandable
    b - the language should be easy to implement

useful implies:
    c -  the language should be more than rdf(s) so that it allows people to
do applications that were inconvenient or impossible with just rdf.
    d - the language should be easy enough to extend to a language that is
more than level 1 (on the way to full OWL).  Thus it should not penalize the
difficulty of extensions.

If we add the explicit goal of covering the represenational needs of 50-75%
of our expected user base, we will almost certainly need to give up on (d)
and possibly (a)  and (b).

So, thinking about the tradeoff of covering a larger percentage of the user
base at the expense of extensibility and possibly understandability, is
worth doing before thursday morning's call.

deborah


Frank van Harmelen wrote:

> The discussion on how to define the compliance levels of OWL will be an
> important issue in the next teleconf.
>
> This email is as a preparation for the teleconf.
>
> We should at least decide on how to reach consensus (although I would
> prefer to actually cut some knots during the teleconf).
>
> Frank.
>    ---
>
> 1. The strategy for defining compliance levels at the Amsterdam F2F and
> immediately afterwards was more or less to include any item in level 1
> for which somebody could make a convincing "frequent/common use" case.
> This lead to top-heavy proposals which were hard to justify because
> they  differed only little from full OWL.
>
> 2. A subgroup met at KR'02 in Toulouse, and explored an alternative
> strategy.
> As explained in messages by me, Deb, Ian a.o., the core of the Toulouse
> proposal was
> to identify a language that would be
>
> - easy to implement (thus encouraging toolbuilders)
> - a sufficient step up from RDF Schema (to justify existence)
> - not prejudice the difficulty of any extentions (partly or full) with
> other elements of OWL
>
> This lead to the proposal of "RDF Schema on steroids" as a compliance
> level 1 for OWL (see [1] for what this includes).
>
> 3. Subsequent discussion revealed that various people would like to have
> additional items in level 1 (e.g. cardinalities, local range
> restrictions). Although none of these by themselves would be hard to
> implement, they are all judged to make it hard to add additional
> features because of the way the features interact.
>
> EXAMPLE: an example is local range restrictions. When interpreted as
> existential ("slot S must have at least one value of type T") they are
> easy to implement, similar when interpreted as universal ("all values of
> slot S must be of type T"), but the combination of these two is hard to
> implement. Thus, including either in level 1 will make it harder to
> extend beyond level 1 and include the other. (Different communities seem
> to have different need for either extension).
>
> 4. The minimal required result at the teleconf is that we agree whether
> the "Toulouse approach" is the right one to take.
> If yes, we can argue the details of "RDF on steroids" as level 1
> If no, we must formulate another strategy for defining level 1 (keeping
> in mind that the "Amsterdam F2F approach" has already shown to lead to
> failure).
>
> Please spend some time thinking all this over before the teleconf.
>
> Frank.
>    ----
> [1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Apr/0329.html

--
 Deborah L. McGuinness
 Knowledge Systems Laboratory
 Gates Computer Science Building, 2A Room 241
 Stanford University, Stanford, CA 94305-9020
 email: dlm@ksl.stanford.edu
 URL: http://ksl.stanford.edu/people/dlm
 (voice) 650 723 9770    (stanford fax) 650 725 5850   (computer fax)  801
705 0941
Received on Wednesday, 1 May 2002 11:33:37 GMT

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