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Re: Monotony

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 15 Oct 2002 17:41:20 -0700
Message-Id: <p05111b00b9d263388acb@[65.217.30.172]>
To: seth@robustai.net
Cc: fmanola@mitre.org, "www-rdf-comments@w3.org" <www-rdf-comments@w3.org>, "Patrick.Stickler@nokia.com" <Patrick.Stickler@nokia.com>

>pat hayes wrote:
>
>>>Frank Manola wrote:
>>>
>>>>More to your
>>>>original point, it seems to me what you want is the ability to control
>>>>or specify when you have monotonicity and when you don't.  Kind of like
>>>>a database transaction mechanism.
>>>
>>>Exactly!   Whatever a  *logical* RDF graph is, it is certainly is 
>>>a document or a cluster of documents - what it is *not* is the 
>>>whole blody semantic web.  Yet we seem not to have any convention 
>>>for RDF authors to state that simple fact about their RDF 
>>>documents and clusters of documents.  But there are many ways that 
>>>this can be implemented without breaking into any new 
>>>specifications.  Well we might need to define some new properties, 
>>>but nothing really major or tramatic.
>>
>>If we have ways of stating the boundaries of 
>>documents/databases/whatever, and of referring to them (perhaps 
>>implicitly) and saying explicitly that something follows from this 
>>bounded thingie alone, then we could say a lot of things that we 
>>are unable to say right now.
>
>Excuse me, where is it written that we cannot say things about these 
>boundries?

The point is not that there are laws preventing you from saying 
anything - clearly there are not - but rather than there are no 
universally agreed WAYS to say this stuff, ie ways that are part of 
an agreed standard. So it is unlikely that anyone else will know what 
you are talking about. I agree that one can invent ways - you and Jos 
DeRoos are two people who spring immediately to mind, not to mention 
Tim B-Lee. BUt until we have one or more of these devices built into 
a standard, i don't think that the world is going to just start 
adopting any of these ways.

>  If I publish a RDF document on the web, it certainly has a URI, 
>and I certainly can say things about that resource (assumed here to 
>be the graph) that has that name.

True, but the RDF spec explicitly disavows any connection between the 
thing denoted by a URI and the document located by that URI if it 
happens to be a URL. I agree this is dumb, and I have no idea why the 
W3C people are so insistent upon it, but that is the official 
position at present.

>  Why can I not say in RDF that this document (or cluster of 
>ducments) either does (or does not) have the Closed World Assumption 
>?

First, there is no way to refer to the document in RDF (see above), 
but more seriously, there is no way to state a closed world 
assumption in RDF, since RDF has no universal quantification. You 
could say it in OWL, however.

>You may find  "Readings about the question: It is said that 
>reasoning on the semantic web must be monotonic.  Why is this so, 
>when human reasoning, which seems to have served us well, is 
>nonmonotonic? "

There is considerable evidence which suggests that human reasoning is 
largely monotonic. (BTW, it is very tricky to argue about what 'human 
reasoning' actually is. The fact is that we have very little idea how 
human beings reason, including ourselves. One thing for sure, our own 
introspections about how we reason are totally wrong; that much has 
been clear for about 50 years now. )

But in any case, the key point here is that reasoning on the semantic 
web is supposed to be done not by people, but by software. If people 
were doing it then it would be the WWW, not the SW.

Pat


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Received on Wednesday, 16 October 2002 10:46:29 GMT

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