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WOWG: compliance levels on next teleconf

From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Date: Wed, 01 May 2002 02:34:53 +0200
Message-ID: <3CCF382D.CE980B51@cs.vu.nl>
To: www-webont-wg@w3.org
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).


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
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

Please spend some time thinking all this over before the teleconf.

[1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Apr/0329.html
Received on Tuesday, 30 April 2002 20:35:36 UTC

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