RE: what is a rule?

From: Wagner, G.R. (G.R.Wagner@tm.tue.nl)
Date: 03/04/03

  • Next message: Wagner, G.R.: "RE: what is a rule?" 
    >> although we can come up with a formal account for a specific type 
>> of rule, I think we should better not try to find a definitive formal 
>> account for "rules", in general. 

> Unless we do, it seems to me that the discussion is vacuous. 
> We literally do not know what we are talking about. 

Notice, you may define KIF, OWL, LBase (or whatever) rules,
but you are not in a position to define "rules", in general.
(Do they define "numbers", in general, or do they rather
define natural, rational, etc. numbers?)

>> At the problem domain level, rules are statements that express 
>> (certain parts of) a business/domain policy (e.g., defining terms 
>> of the domain language, defining or constraining domain operations) 
>> in a declarative manner

> Please say what is meant by 'declarative' here. 

"Declarative", here, means not specìfying the details of how to 
implement a policy but only specifying what constitutes the policy
at the highest level of description (with preconditions and
postconditions of implied actions).

"If any 3 of the named analysts report a strong buy on the same  stock
within the same day and before the market closes, then buy 1000 units  of
that stock."

>> At the (platform-independent) computational level, rules are formal  
>> statements that operationalize domain policies and can be easily mapped 
>> into executable statements of a programming platform.

> That seems to cover any programming platform at all. 

Not really, because you want to have a kind of direct support here.
E.g., SQL systems directly support many important types of integrity
constraints (by means of CHECK, CONSTRAINT and ASSERTION statements), 
while C++ and Java do not.

>> Rule languages used at this level are RuleML 0.82, SQL-99, OCL 2.0, ISO
Prolog or KIF.

> KIF is purely an assertional logic, and cannot be 'easily mapped' into 
> executable statements. 

So, KIF rules cannot be interpreted/executed by any inference engine?

>> They may, for instance, specify reactions (e.g. for specifying the 
>> reactive behavior of a system/agent in response to events) 

> in what sense is a 'reaction' anything to do with reasoning?? 

I normally reason before I react :-)

-Gerd

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