JESS: backchaining and the logical CE

[Timothy Redmond]

I have found an interaction between the logical keyword and the  
backchaining facility which is either a bug or something I don't  
understand.

Suppose that I am doing backchaining with a template foo:
(deftemplate foo
  (declare (backchain-reactive TRUE))
  (slot x)
  (slot y))
It turns out that the rule:
(defrule getFoo
  (logical (enableGetFoo))
  (logical (need-foo (x  ?x)))
  (logical (adder (z ?z)))
  =>
  (assert (foo (x ?x) (y (+ ?x ?z)))))
doesn't seem to work.  This rule will not activate or fire even when  
all the preconditions are satisfied.

If I take out the logical keyword, things appear to work as expected.   
The getFoo rule fires when I need a foo but the logical support is not  
there.

If I move the "(logical (enableGetFoo))" line below the need-foo line,  
then the rule works exactly as I need.  (This is what I actually did in  
my application.)

I put the "adder" predicate in this example to show why I would be  
putting a logical around a "need-foo".  It is because there are other  
items on the LHS of my rule that I want to be logical but that I don't  
want to put before the "need-foo".

Is this expected behavior?  I have included a file below - sorry  for  
the complexity.

-Timothy
------------------------------------------------------------------------ 
-----------------

(deftemplate foo
  (declare (backchain-reactive TRUE))
  (slot x)
  (slot y))
(deftemplate adder
  (slot z))
(defrule getFoo
  (logical (enableGetFoo))
  (logical (need-foo (x  ?x)))
  (logical (adder (z ?z)))
  =>
  (assert (foo (x ?x) (y (+ ?x ?z)))))
(defrule doPropagate
  (logical (propagate ?x))
  (logical (foo (x ?x) (y ?y)))
  =>
  (assert (foobar ?y)))
(reset)
(watch all)
(bind ?fact (assert (adder (z 8))))
(assert (propagate 3))
(assert (enableGetFoo))
(printout t "starting run" crlf)
(run)
(printout t "finishing run" crlf)
(modify ?fact (z 11))
(printout t "starting run" crlf)
(run)
(printout t "finishing run" crlf)
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