Re: Nonmonotonic rules

Pat,

This is a powerful statement, but I would like to see it backed up with
examples of purely monotonic rules that are worth publishing.

The brittleness argument against non-monotonic reasoning is a red
herring. People use non-monotonic reasoning in their daily life because it
is useful most of the time. I see no reason why Semantic Web should be
different.

While I haven't seen any convincing examples of monotonic rules that would
cause me to want to send my agent and scoop them up, I do see reasons why I
might want to have non-monotonic knowledge to be published. This is
because most (if not all) rule-based applications that I've looked at use
some kind of non-monotonicity. If anything, I'd like them to be published
so I could steal them :-)

Seriously, though, suppose there is a service, say, a travel reservation
service that specializes in multi-segment complex travel arrangements.
Of necessity, such a service is going to use a form of closed-world
assumption, since it will be looking only at a small subset of all
available resources and make its recommendations based on that incomplete
knowledge. If it can't find a car rental somewhere, it will assume there
isn't one and will try to find the next best alternative.

Why would I want to have some specification of such a service published?
Because I might be able to reason about how the service works. This service
may require multiple interactions and my credit card may be charged several
times. I might determine, for example, that the service won't charge my
card unless there is a way to back out of the corresponding part of the
deal or there is travel insurance provided, or .... 


	--michael  


pat hayes <phayes@ihmc.us> writes:
>
> Re. the (forever ongoing and interminable) debate about the merits of 
> otherwise of nonmon reasoning.
> 
> Bottom line: nonmon reasoning is brittle (by definition) but can be 
> very efficient. So when you know it won't break, by all means use it. 
> But it seems to me that it is up to its proponents to justify or 
> explain how we can have nonmon formalisms being used in a Webbish 
> context, where the brittleness (or if you prefer, 
> context-sensitivity) seems on the face of it to be an unsurmountable 
> barrier to deployment, since there is no way for a reader of some 
> nonmon rules to know what the intended context is; and when used out 
> of context, nonmon rules are almost always wrong, and can produce 
> potentially dangerous errors. (Note, this is only referring to the 
> *publication* of nonmon rules on a Web, not to their *use* in some 
> application where it is known they are appropriate, or one is willing 
> to take the risk of using them in any case.)
> 
> So far, the only response Ive heard on this point is a kind of 
> blustery denial: a claim that the Sweb just isn't going to be like 
> the WWWeb, but more like an intranet, where all the users will just 
> know, or will be told by the owner, or will agree among themselves in 
> managers' meetings, which worlds are closed and which namespaces 
> satisfy the unique-names assumption and so on; so the problem will be 
> avoided by what might be called Web-external contextual agreements. I 
> refuse to take this answer seriously: it seems to me to just be a 
> statement to the effect that one is not working on the semantic web 
> at all.
> 
> Anyone got any other answers? Until someone has, I would suggest that 
> all talk about nonmon systems be ruled out of order.  Its not enough 
> to observe in a general kind of way that nonmon systems are useful 
> (no argument) or that they are in widespread use and all the best 
> companies have them and they make a lot of money (irrelevant) or that 
> they solve this or that famous problem (they usually don't, in any 
> case). There is a basic technical issue that needs to be addressed. 
> Address it, or else please shut up about them.
> 
> Pat
> 
> -- 
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Received on Thursday, 15 January 2004 17:38:07 UTC