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Re: Requirements Document

From: Jim Hendler <hendler@cs.umd.edu>
Date: Thu, 14 Feb 2002 18:00:48 -0500
Message-Id: <p05101402b891ed4e6c5f@[129.2.178.147]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, heflin@cse.lehigh.edu
Cc: www-webont-wg@w3.org
(Chair neutrality remains on for this one - these are attempts to 
clarify what I think sense of the WG was at the f2f, and requests for 
clarification with respect to the comments - in many cases I agree 
with Peter's point, but want to make sure the WG understands what was 
voted on at the f2f (since I took the notes) and make sure the points 
match up)

At 2:03 PM -0500 2/14/02, Peter F. Patel-Schneider wrote:
>From: Jeff Heflin <heflin@cse.lehigh.edu>
>Subject: Re: Requirements Document
>Date: Thu, 14 Feb 2002 13:23:11 -0500
>
>>  Peter,
>>
>[...]
>>  3) You had a problem with the "Referencing with URIs" requirement. In
>>  subsequent discussion with Dan, it appears that you would be happy if we
>>  change the wording to "URIs + frag[]ment ids."
>>
>>  ACTION: Wording for the requirement will mention "frag[]ment ids."
>
>No, this would not make me happy.  In my discussion with Dan, I stated that
>I wanted to be able to refer to anything on the web, and things outside of
>the web, as well.  Unfortunately, URIs plus fragments does not get us
>there, because XML Schema document definitions cannot be so addressed.
>
>I don't know why this unfortunate state of affairs exists, but the
>*requirement* should therefore be, in my mind at least, the ability to
>reference what we need to reference, including XML Schema document
>definitions.  URIs plus fragments gets us 99% of the way there, and may be
>what we end up using, but changing from what we want to a partial solution
>for what we want is, in my view, not something that should be done in a
>requirements document.

   The requirement says we must be able to reference with URIs, it 
doesn't say anything about that being the only thing to use. I 
believe this is consistent with what I heard at the f2f.  Also,  I 
don't see what in your discussions makes you want to remove this 
requirement.

  If you're suggesting we could add to the objectives the ability to 
refer to things on and off the web, etc - that is fine with me and I 
believe it would be consistent with discussion at the f2f, however, I 
think what is written is a requirement that got an A vote at the f2f, 
which means you did not vote against it previously -  Please clarify 
what change should be made to the document and why you are changing 
your vote if you are.
(Remember we are talking necessary conditions, not sufficient).

>[...]
>
>>  5) You believe the "Ability to state closed worlds" requirement is too
>>  strong. Once again, this was a requirement that a significant number of
>>  people think is essential. Obviously, we can't make a closed-world
>>  assumption, but the ability to infer negative information from the
>>  absence of positive information is useful. However, I understand your
>>  concern in that this is not a feature found in existing langauges and
>>  may be difficult to implement.
>>
>>  ACTION: We will demote "Ability to state closed worlds" to an objective.
>>  If anyone wishes to argue for it remaining a requirement, please do so.
>
>It is not just that it is difficult to implement, but that the closure of
>a general ontology is not well defined.
>
>For example, what is the closure of
>
>	John is a Person whose sisters include either Jill or Susan or
>	whose brother is Bill.

my understanding of the requirement expressed at the f2f was that by 
closing the world we wanted someway to designate a document (or other 
designation of a set of Owl triples) and let a reasoner know that it 
could consider this a closed world if it wished.  If you feel the 
document doesn't explain this right, you should suggest wording 
changes.  Also, I recorded that the discussion at the f2f suggested 
this could be "extra-logical" (although to be honest, I'm not quite 
sure what that would mean).

>  > 6) You take issue with "At a minimum, the language should recommend to
>>  users how they can specify their own default mechanisms." If I recall
>>  correctly, this was a resolution made by the group at a recent telecon
>  > after considerable debate on defaults.
>>
>>  ACTION: The requirement will remain unchanged.
>
>Umm, this is an objective, not a requirement, I believe.

Peter is right - Jeff, are you proposing to make it a requirement? 
If so, it would need to be changed to a language feature - as "making 
a recommendation" applies to a document, not to a language.

>
>If someone can figure out how to ``recommend to users how they can specify
>their own default mechanisms'' in a reasonable fashion, I would be very
>happy.  However, I don't have a clue as to how to progress towards meeting
>this objective.

That is fine, it doesn't negate the fact it is an objective - we've 
already agreed that the objectives may not be achieved.  If those 
people who like defaults can find an idiom they are happy with (like 
the one you and Ian presented at the f2f) then this objective is 
partially met. However, at the f2f I think what people wanted was to 
be able to specify defaults, not default mechanisms, therefore we 
might consider a wording change (i.e. to let people specify defaults, 
not default mechanism)
-- 
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
Received on Thursday, 14 February 2002 18:00:58 GMT

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