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Re: Monotony

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 11 Oct 2002 10:26:46 -0500
Message-Id: <p05111b05b9cc9b734ab2@[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>

>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. And it wouldn't be rocket science to provide 
for saying things like this. No argument there. But that is (or can 
be) all monotonic. What is non-monotonic is using inference which 
makes these 'closed-world' assumptions *without saying or recording 
that it has made them*. And the reason why that isn't a good idea on 
the web (or indeed in any large-scale communicative context, such as 
human society) is that unless your listener shares your unspoken 
assumptions, they can draw incorrect and unintended conclusions from 
what you tell them. That is why non-monotonicity is dangerous.

Of course people make mistakes, change their minds, correct their 
mistakes, etc. BUt the fact that we use a vocabulary to talk about 
this that talks of CHANGE is itself a tribute to the need to have a 
monotonic underlying logic. If I tell you that Joe is a bird, you 
conclude that Joe can fly, and I then tell you that Joe is a penguin, 
who made the mistake? We might argue about this - I think you did, by 
assuming more than I told you - but the nonmonotonic answer is, what 
mistake? There never was a mistake. You concluded Joe could fly, now 
you conclude he can't fly: so?. Nonmonotonic logic changes the 
logical rules to accommodate to the current state of belief. 
Monotonic logic says, you had to change your mind or you would now be 
inconsistent. I think that like the rest of us you probably do 
actually think using a monotonic logic.

Pat
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Received on Friday, 11 October 2002 13:54:18 GMT

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