This isn't a trivial question, but the answer is still simple:
basically, yes.
Jess's rule language is not the predicate calculus, and rules are
declarative and active. The "=>" ("implies") of predicate calculus is
an entirely different thing than the "=>" of Jess, which is best read
as "then". Jess rules are like active if-then statements -- if X, then
-do- Y. If you need rules to enforce logical statements, then yes, the
only way to do it is as you've shown here.
I think Francois Keegan wrote:
> Hello,
> I'm sorry if the question is trivial, maybe I've miss
> something in the manual..
> I wonder how to write something like:
>
> P(x) => not A(x)
>
> in jess. The only (tricky) way I found is:
>
> (defrule r
> (declare (salience MAX_VALUE))
> (P ?x)
> ?f <- (A ?x)
> =>
> (retract ?f)
> )
>
> An what about:
> P(x) => A(x) or B(x)
>
> do I have to write two rules?:
> (defrule r1
> P(x)
> (not (A ?x))
> =>
> (assert (B ?x))
> )
>
> (defrule r2
> P(x)
> (not (B ?x))
> =>
> (assert (A ?x))
> )
>
> Am I wrong if I say:
> the LHS can contain everything (neg, and or)
> and the RHS must contain
> a conjunction?
>
> thankfully,
> Francois
>
>
>
>
>
>
>
>
>
>
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Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
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