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Fwd: Re: MT for imports

From: Jim Hendler <hendler@cs.umd.edu>
Date: Thu, 14 Nov 2002 11:08:47 -0500
Message-Id: <p05111736b9f97afecb24@[10.0.1.2]>
To: webont <www-webont-wg@w3.org>
Oops, more from me and Peter, I meant to cc to the group

>Date: Thu, 14 Nov 2002 10:27:37 -0500
>To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
>From: Jim Hendler <hendler@cs.umd.edu>
>Subject: Re: MT for imports
>Cc:
>Bcc:
>X-Attachments:
>
>>From: Jim Hendler <hendler@cs.umd.edu>
>>Subject: RE: MT for imports (was: Re: Imports Proposal)
>>Date: Thu, 14 Nov 2002 09:46:36 -0500
>>
>>>
>>>  Jerome- I understood what you wanted, and I didn't mean nonmon in a
>>>  formal sense.  But suppose I was using the SW for e-commerce and we
>>>  had a situation where
>>>
>>>  Document 1 says:
>>>    I sell pencils
>>>    pencils are a document2:commodity
>>
>>I don't see how you can negotiate to buy pencils when this is all that you
>>know.  You don't know pricing, etc.
>
>come on Peter, I was simplifying for the sake of the example -- 
>assume I put in some ...s and give me credit for not being totally 
>stupid.
>
>>  > Document 2 says:
>>>    Commodity has restriction onproperty "quantity" of numeral 1000.
>>>  (i.e. commodities are sold in lots of 1000)
>>>
>>>  Then if document 2 is down and I negotiate to buy a pencil from
>>>  document 1, when document 2 comes back up, I suddenly find I have to
>>>  pay for 999 more pencils than I wanted.
>>
>>Well, if what you wanted to do was to buy one pencil, then you tried to do
>>something that was not possible.  When all the information is known, a
>>contradiction should result.
>
>why was it not possible?  at the time that I was talking to Document 
>1, it had no reason to know that commodities are not sold in single 
>units -- I'm really not trying to formalize the buying of pencils - 
>I'm trying to point out that when documents are linked together, the 
>meaning of the whole requires that they all be there - otherwise 
>even in a monotonic system there could be missing information that 
>could have a negative effect (in fact, I'm pretty sure that when Ron 
>Brachman presented the paper you guys did on using Classic in the 
>real world, he used an example of a procedural attachment that 
>failed if the program it tried to run failed).  When the information 
>is know a contradicition should result - that's exactly my point - 
>we agree.
>
>>
>>If what you wanted to do was to buy some one quantity of some good that had
>>``pencil'' in its description for some known or unknown price, then that
>>happened.  The fact that you assumed that the good was a single pencil when
>>that information was not available to you is your problem.
>>
>>>  If we assume that imports is used to mean "My meaning relies on the
>>>  meaning of the other document" in any real sense, then if that
>>>  document is missing, what does the first document mean?
>>
>>It means what it says it means.  Imports should not be read as ``My meaning
>>*relies* on the meaning of the other document''.  It should instead be read
>>as ``Part of my meaning is contained in that other document''.  Then if
>>that document cannot be found all that has happened is that not all
>>relevant information can be accessed.
>
>ok, this is fine - but then I would expect to do the same thing I 
>would do if I went to read your single ontology document and found 
>it referred to some classes that didn't seem to be there (perhaps 
>because I only read part of it before some server crashed).  I don't 
>know what that would be formally, but practically I would hope my 
>system would return a "class undefined" error or something like that 
>rather than blithely assuming that everything was just fine.
>
>>  > My proposal is simply to do what programming languages do - if I say
>>>    include foo.h
>>>  and foo.h can't be found for some reason, the program simply returns
>>>  an error, rather than trying to compile - because you said it needs
>>>  foo.h to run correctly and it knows that means it could possibly
>>>  return erroneous values even if it compiles okay without it.
>>
>>Well, I would hope that we can do a bit better.
>>
>>The analogy I would like to make is that if all the information that is
>>needed can be found in the accessible documents, then the unavailability of
>>the other documents can be handled in ways different from throwing an error.
>
>are we going to specify them?  I hope not, because then we'll never 
>get to CR in the next few weeks - unless there's a whole literature 
>I don't know about, I would assume that dealing with missing 
>information is not a solved problem.
>
>>
>>>  I actually expect the ontology documents to be relatively robust, so
>>>  I don't think this is something we need to worry about a lot - but I
>>>  think having a strong imports with "graceful degradation" is
>>>  contradictory in settings like ecommerce where real money changes
>>>  hands
>>
>>I don't see how this follows.  In some cases the inability to obtain the
>>information in imported document will cause important consequences to be
>>underivable resulting in the transaction not being completed.  In other
>>cases sufficient information will be available and the transaction could be
>>completed.
>
>and how will you know?
>
>>Applications that make (unwarranted) conclusions from the absence of
>>information will, of course, potentially do the wrong thing.  This is one
>>reason to not write such applications or, at least, to require that they
>>worry about incompleteness.
>
>duuuh, which is why I said what I did in the first place -- that 
>when a document is missing we don't want graceful degradation or the 
>system using the first document won't know that there might be 
>missing information - I don't care how we do it - but if something 
>doesn't let me know a document was missing in the imports closure, 
>then I cannot know that there might be missing information.
>
>I really do think we are agreeing, not disagreeing.
>  -JH
>
>--
>
>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


-- 
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 11:08:53 GMT

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