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Re: Proposal to close issue 5.6 - owl:imports

From: Jim Hendler <hendler@cs.umd.edu>
Date: Thu, 14 Nov 2002 11:31:35 -0500
Message-Id: <p05111739b9f97e1283e4@[10.0.1.2]>
To: Jeff Heflin <heflin@cse.lehigh.edu>
Cc: webont <www-webont-wg@w3.org>

At 11:14 AM -0500 11/14/02, Jeff Heflin wrote:
>Jim,
>
>To me, this proposal has the same effect as postponing the issue. We
>still have a fundamental problem:
>
>If there is no form of imports (whether implicit in namespace usage or
>explicit), then the use of terms from an ontology is meaningless.

Jeff, I didn't expect you to agree with it, but we cannot go to a 
vote without something to vote on.  However, I don't think your 
objections below are applicable.

>
>That is, if I have two documents:
>
>doc1:
>Man subClassOf Mortal
>
>doc2a:
>xmlns:d1="doc1"
>Socrates type d1:Man
>
>Then is Socrates type Mortal? We need to take a position on this. With
>implicit imports, then the answer is yes. With explicit imports, the
>answers is no. To get the same effect you would have to say:
>
>doc2b:
>xmlns:d1="doc1"
>doc2b imports doc1
>Socrates type d1:Man

but the GUIDE document (which I included in my proposal) makes it 
absolutely clear that the expectation in this case is that he is a 
mortal man for doc2b.  It even has an example with respect to wine 
and food that makes this clear.  The reference document also says 
that if doc1 were to import another doc, then that stuff would be 
included as well.

In fact, my proposal specifically addresses Frank's concern we have 
no imports by specifically embracing the current wording in Guide and 
Ref that says we absolutely do have imports (although I suggest 
renaming it, whatever we do)
  -JH



>However, if the semantics do not specify which position we take, then we
>lose interoperability. Two users may look at doc2a and disagree about
>whether or not there is an implicit imports, and thus whether or not
>doc2a implies Socrates is Mortal. The whole point of a formal semantics
>is to make it absolutely clear who is right is such situations.
>Therefore, I cannot support your proposal.

WHY????  Why does the SEMANTICS have to say this -- the minute you 
show me the SEMANTIC document that shows how you do an include in C 
or Fortran or any other widely used programming language, then I will 
begin to believe this. I have been using include statements in my 
programming literally since the time you were in diapers, and have 
never, in any of my courses, encountered any semantics (other than 
operational, and even that vague) - and I have a PhD in Computer 
Science and took courses in operating systems, programming languages, 
parsing, and all that other good stuff - it's this hang up on a 
formal semantics for this well-understood and easy to implement 
feature that has me confused.

>There have been various proposals on the table that give an umabiguous
>semantics for imports. It seems like the one thing that worries some
>people is the time-varying nature of the Web.

yes, that is very worrying to many of us

>
>I propose that we go with either my latest proposal [1]

which Peter sent problems with and no one has rewritten as far as I can tell

>or Pat's take on
>it [2],

which is different, and also created a long line of discussion

>with the following additional wording to address time
>dependency:
>
>The Web is highly dynamic, and pages can change or disappear at any
>time. However, a model theoretic semantics is used to assign meaning to
>a static set of statements. To address this issue, the semantics for OWL
>give meaning to a set of docuements with respect to the state of the Web
>at some fixed point in time.
>
>Jeff
>
>[1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Nov/0004.html
>[2] http://lists.w3.org/Archives/Public/www-webont-wg/2002Nov/0099.html

if you will cut and paste a specific proposal together, describe how 
it addresses the objections and put it on the table, I'll be willing 
to entertain a vote on that instead of mine - and don't claim this is 
last minute - an action to do exactly that was taken last week, and I 
only did mine because no such proposal materialized.

-- 
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)
Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
http://www.cs.umd.edu/users/hendler
Received on Thursday, 14 November 2002 11:31:40 GMT

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