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Re: LANG: compliance levels

From: Enrico Motta <e.motta@open.ac.uk>
Date: Wed, 1 May 2002 17:52:06 +0100
Message-Id: <p0510031bb8f5c92cdd55@[212.126.147.108]>
To: Deborah McGuinness <dlm@KSL.Stanford.EDU>, Enrico Motta <e.motta@open.ac.uk>
Cc: www-webont-wg@w3.org
At 5:34 pm -0700 28/4/02, Deborah McGuinness wrote:
>
>>  Can't one define existentially qualified range restrictions by having
>>  local ranges + min-cardinality? Or are they something else?
>
>with universally qualified range restrictions  one can say things 
>such as "all my
>children are doctors"
>and with min cardinality  one can say things such as "i have at 
>least one child"
>but in combination that only allows one to say  I have at least one child  and
>ALL my children are doctors.
>This DOES  imply that I have at least one child who is a doctor.
>BUT it does not allow you to state the full generality of 
>existentially qualified
>range restrictions - for example there is no conceptually good way 
>way to state
>(or imply) with just min cardinality and local ranges for example that I also
>have at least one child who is a lawyer after I have stated the previous
>information about my children being doctors.
>
>If one has disjunction in the language, I could make a disjunctive class of
>Doctor OR Lawyer and then state that all my children are instances 
>of this class
>and then state that I have at least 2 children, but  I would not be 
>stating that
>one child is a doctor and one is a lawyer.
>Even without disjunction, I could state that Doctor and Lawyer are both
>subclasses of the class DoctorOrLawyer  thereby effectively getting 
>the notion of
>disjunction.
>If we have disjointness or negation, I can also state that the 
>classes Doctor and
>Lawyer are disjoint.
>With negation, I can also state that a particular child is an instance of the
>class Not Doctor...
>All this is showing ways of getting some of the information   but 
>not getting the
>full notion of existentially qualified range restrictions.


OK, got it!

>
>We will not be expecting all tool developers to support cardinality 
>- just those
>that are interested in marketing to segments that find them critical.  In my
>opinion, this will be many but not all tool developers.  The reason I do not
>expect all tool developers to support this (in all of their 
>deployments) is that
>one can gain some efficiencies by making limitations to the language and some
>communities will be more interested in the efficiencies than in a 
>more expressive
>language.
>
>Our small group strategy was to
>1 - come up with an agreement on a small language that hopefully many tool
>developers will support
>2 - attempt to get the most useful features in this small language
>3 - keep the small language small - thus we explicitly were not taking the
>strategy of including everyone's favorite constructor for which they 
>could make a
>compelling argument.
>4 - not penalize too heaviliy tool developers who want to add 
>construct XX to the
>core language.
>
>3 & 4 were the hardest to maintain however we all believed them to 
>be important.
>for example if we put in existentially qualified range restrictions 
>in the core
>language, we penalize tool developers who need universally qualified range
>restrictions but could live without existentially qualified range 
>restrictions.
>And conversely, if we put in universally qualified range 
>restrictions in the core
>language, then we penalize tool developers who need existentially 
>qualified range
>restrictions but could live without universally qualified range restrictions.

I see your point but I am still not 100% convinced. It is a tricky 
one because we are heavily relying on our subjective impressions of 
what users want.  And I am worried that if OWL level 1 is only a 
small improvement over rdfs, then it loses its raison d'etre.  The 
counter-argument is that tool developers will then add the 
functionalities they consider important.  But even this is not 
totally convincing, because they won't necessarily be in a better 
position than us to make a decision and I guess many (most?) tool 
developers  expect us to make such  a decision. So, on balance I 
would still say that  not to have any kind of local range restriction 
is probably the worst decision and if we have to choose my feeling 
remains that universal local restrictions are probably what people 
are used to.  But this is only a 'feeling' and it may be useful to 
poll the members of this wg to get additional data.

In any case, we are definitely moving in the right search 
neighbourood, which is a major improvement!

Enrico

-- 
Enrico Motta, PhD                   
Director, Knowledge Media Institute
The Open University
Walton Hall
Milton Keynes, MK7 6AA
United Kingdom

URL: http://kmi.open.ac.uk/people/motta
Tel: +44 1908 653506
Fax: +44 1908 653169
Received on Wednesday, 1 May 2002 12:52:16 GMT

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