Re: Nonmonotonic rules

pat hayes wrote:

>
>> On Jan 21, 2004, at 3:15 AM, Michael Kifer wrote:
>> [snip]
>>
>>>> Indeed. There may be no differences, given my newer understanding of
>>>> how you intend that nonmon rules are to be used. I think we may have
>>>> been viewing the world from  different metalevels, as it were.
>>>
>>>
>>> Suddenly the difference of opinion became fuzzy ...
>>>
>>> Unfortunately, nobody had the patience to read this far to find out 
>>> that we
>>> actually agree :-)
>>
>> [snip]
>>
>> I have, FWIW, but I'm not sure what to make of this agreement. Once 
>> more, it may be at the level of nuts and bolts that the blood will 
>> start to flow :)
>
>
> Actually, I don't think so. Getting a bit closer to the nuts and bolts 
> makes things clearer (for me, at least).
>
> Its interesting that this disagreement/misunderstanding can be rooted 
> in the differences between two world-views of what class-based 
> reasoning is really *for*, one based on DL's evolution from logic, the 
> other based on schemas considered as data descriptions. This 
> difference of perspectives keeps coming up and seems to be very 
> important: for example, does one think of range assertions as 
> constraints (datatype) or simply as assertions (logic)? How about 
> datatyping? And so on. We keep running into cases where people have 
> divergent intuitions which can be traced back to the differences in 
> attitude arising from these two world-views.


A related intersection of world views keeps coming up in linguistics, 
where it appears as the descriptive vs. the prescriptive view of what 
grammar is (or does).

Some quick pointers:
http://www.linguistlist.org/~ask-ling/archive-most-recent/msg03443.html
http://en2.wikipedia.org/wiki/Grammar

Jeff

>   Clearly at some level they are similar: Codd's Relational model and 
> the DL logic-based semantics all agree on the ultimate nature of 
> relations and classes; but the ways that the two communities think 
> seem often to be sharply different.  Im not sure how to characterize 
> the difference, exactly, but it seems to be that the DB world-view 
> sees a sharp distinction between different kinds of information, and 
> tends to treat general facts as conditions imposed on concrete facts: 
> meta-data as opposed to data.  Distinctions like this may be 
> operationally important but have no natural place in a logic-based 
> perspective which historically has been largely motivated by the 
> desire to unify divergent sources of information as far as possible 
> into one uniform framework.
>
> If one thinks of a universally quantifier assertion as really being 
> meta-data, i.e. as being about the ground facts rather than just 
> another fact about the world, then this lends itself immediately to a 
> host of what seem to someone coming from the logical tradition to be 
> basically errors: things like considering Herbrand interpretations to 
> be a fully adequate semantic theory; like finding various nonmonotonic 
> techniques natural (even obvious) and thinking of quantifiers are 
> essentially substitutional, all of which are anathema to logicians. 
> And if you think that the more general assertion's chief purpose is to 
> control, select or check the internal coherence of a body of ground 
> data, then the purely logical account of quantification is inadequate 
> or at any rate incomplete, since a combination like
> (forall (x) (R x x))
> (not (R a a ))
> is of course inconsistent, but inconsistent in a special way: the 
> second item is wrong, or should be rejected, as it fails to conform to 
> the schema. The schema has more assertional force than the mere data 
> in a DB world, since the schema is a kind of filter or guardian of the 
> data. Logic has nothing to say about intuitions like this.
>
> Anyway, just rambling. It might be fun to try to get this divergence 
> between world-views stated clearly, though, as the SW world seems to 
> require DB folk and logic folk to be able to get along with one another.
>
> Pat
>
>
>> Cheers,
>> Bijan Parsia.
>
>
>

Received on Thursday, 22 January 2004 12:09:28 UTC