This can be considered a continuation of the post "Nested not/and
syntax question"
With the help of Ernest, the following two bugs in rule compilation
have been identified.
A. Pattern (not (and ( ?var <- ...)))
The following rule is erroneously compiled.
(defrule Rule1bug
(not
(and
?o <- (Object (name A))
(Pred (obj ?o))
)
)
=>
(printout t "OK1" crlf))
Specifically, variable ?o inside the Pred fact obtains a new name, as
shown by the (ppdefrule) output, leading to wrong results:
(ppdefrule Rule1bug)
"(defrule MAIN::Rule1bug
(initial-fact)
(not ?o <- (and ?o <- (Object (name A)) (Pred (obj ?_021_o))))
=>
(printout t \"OK1\" crlf))"
One easy way to come around this bug is to add a test pattern, instead
of using explicit variable matching. Eg:
(defrule Rule1fixed
(not
(and
?o <- (Object (name A))
(Pred (obj ?o2))
(test (eq ?o ?o2))
)
)
=>
(printout t "OK1" crlf))
B. Pattern (or (..) (and ( ?var <- ...)))
Now the compilation of the outermost (or ) and its contents is
perfomed correctly, but whatever pattern is added to the lhs of the
rule outside (i.e., after) the (or ..) ends up insided it somehow. Eg:
(defrule Rule2bug
(or
(not (Object (name C)))
(and ?o <- (Object (name C))
(not (Pred (obj ?o)))
)
)
(test (eq 1 1))
=>
(printout t "OK2" crlf))
The (ppdefrule) output shows that the (test ) pattern is included in
the (and ) pattern. In fact, no statement following the (or ) pattern
can in practice appear outside it:
Jess> (ppdefrule Rule2bug)
"(defrule MAIN::Rule2bug
(or
(and
(initial-fact)
(not (Object (name C))))
(and
?o <- (Object (name C))
(not (and (Pred (obj ?o))
(test (eq 1 2))))))
=>
(printout t \"OK2\" crlf))"
I still can't figure out a way to overcome this bug. Notice that both
Rule1bug/fixed and Rule2bug express the same logical statement,
therefore the fixed rule can be used as a potential solution in this
case.
Theodore
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