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Re: [UCR] RIF needs different reasoning methods

From: Francois Bry <bry@ifi.lmu.de>
Date: Wed, 08 Mar 2006 11:33:27 +0100
Message-ID: <440EB2F7.4050909@ifi.lmu.de>
To: edbark@nist.gov
CC: public-rif-wg@w3.org

Ed Barkmeyer wrote:
>> If a normative rule says
>>   all x p(x) => q(x) or r(x)
>> and r(y) is removed, then the reactive rule to be evaluated is:
>> ON remove r(y) CHECK (p(y) => q(y))
>> Note that y is bound by the event "remove r(y)".
>
> Thank you for this clarification.  I completely misunderstood
> "reactive rules".
>
> It seems to me that identifying "all x p(x) => q(x) or r(x)" as a
> "normative rule", however, is sufficient.
It surely might be sufficient. My point is that a RIF making it possible
to express the above mentioned reactive rule from a normative rule would
be very usefull in practice.

What i am suggesting with rthis example is a "bridge" beween the
declarative and reactive fragments of RIF. I think, there is need for
such a bridge in many applications -- e.g. database-like applications.
> Further, I am concerned about the semantics of "remove".
This is a good point. Such a semantics is not trivial to define. But we
must go through: Without semantics for actions lijke "remove" RIF cannot
have reactive rules, I think.
> Does some Use Case make "remove" a clear requirement?
There were some UC I contributed to that mention "removals".
> OK.  But what I meant was that I cannot determine whether
>  IF <antecedent> THEN <consequent>
> is a "deductive rule" or a "normative rule" from such a syntax, when
> the consequent is an "assertion".  To distinguish them, I would need
> two keywords, e.g. THEN and CHECK.
Agreed. Instead of keywords at the rule level, we could have
annotations. I would favour annotations because they would make easier
to receive a rule of the one kind and to use it after the other kind.
There is a need for this, too.
> I agree, but the concept of "inconsistent" now means two things:
> - there is an explicit or implied contradiction: p(x) AND NOT p(x), or
> - some normative rule has been violated.
The second case implies the first, if normative and deduction rules are
put together and as you say:
> I think these are only equivalent if the semantics of the normative
> rule is the contrapositive, or you have NAF semantics for the relevant
> predicates.
>
>>> It strikes me that we may get very close to implementation issues in
>>> defining the semantics of rulesets (as the interchange between Bijan
>>> and François suggests) or we may get perilously close to
>>> distinguishing the purpose of the exchange.
>>
>> Maybe. If we don't, my thesis is that RIF will remain an interesting
>> academic exercise - something I can live with. But could the WG live
>> with it?
>
> And if we do, will Dr. FrankenRIF be able to live with his monster?
:-)

Regards,

Francois
Received on Wednesday, 8 March 2006 10:33:37 GMT

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