If you can split rule-2 into two rules, you can say something like
(defrule rule-2a
(MyObj
(id ?id)
(OBJECT ?obj)
)
(id ?id)
(not (first-id ?id))
=>
(assert (first-id ?id))
)
(defrule rule-2b
(MyObj
(id ?id)
(OBJECT ?obj)
)
(exists (first-id ?id))
=>
(myfunction ?obj)
)
I *think* this is equivalent to what you're trying to do.
I think David Korz wrote:
> I want to have a rule that fires for a definstance when it is created
> and other rules from when it is subsequently updated. The update rules
> should not fire when the definstance is created, only when it is
> updated. I can get a rule to first just once for a definstance but the
> only way I could get a rule to fire only on updates was to use a
> defquery on the RHS. Is there a better way to do this?
>
> MyObj is the definstance for a bean with id as a property.
>
> ; Rule that runs once for a definstance.
> ; Assert a fact so we never do it twice.
> (defrule rule-1
> (MyObj
> (id ?id)
> (OBJECT ?obj)
> )
> (not (id ?id))
> =>
> (assert (id ?id))
> (myfunction1 ?obj)
> )
>
> ; Rule for updates.
> (defrule rule-2
> (MyObj
> (id ?id)
> (OBJECT ?obj)
> )
> (id ?id)
> =>
> (bind ?i (count-query-results find-first-id ?id))
> (if (> ?i 0) then
> (myfunction2 ?obj)
> else
> (assert (first-id ?id))
> )
> )
>
> (defquery find-first-id
> "Look for first-id fact for id"
> (declare (variables ?id))
> (first-id ?id)
> )
>
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---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://herzberg.ca.sandia.gov
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