Hi, I have been trying to understand the slot-specific functionality which is described in the JESS manual as follows:
--------------------------------------------------- 6.18. The 'slot-specific' declaration for deftemplates Deftemplate definitions can now include a "declare" section just as defrules can. There are several different properties that can be declared. One is "slot-specific". A template with this declaration will be matched in a special way: if a fact, created from such a template, which matches the left-hand-side of a rule is modified, the result depends on whether the modified slot is named in the pattern used to match the fact. As an example, consider the following: Jess> (deftemplate D (declare (slot-specific TRUE)) (slot A) (slot B)) Jess> (defrule R ?d <- (D (A 1)) => (modify ?d (B 3))) Without the "slot-specific" declaration, this rule would enter an endless loop, because it modifies a fact matched on the LHS in such a way that the modified fact will still match. With the declaration, it can simply fire once. This behavior is actually what many new users expect as the default; the technical term for it is refraction. -------------------------------------------------- I tried the following without the slot-specific declaration, expecting an infinite loop to occur: (reset) (deftemplate D (slot A) (slot B)) (defrule R ?d <- (D (A 1)) => (modify ?d (B 3))) (bind ?f (assert (D (A 1)))) (facts) (run) (facts) But I got the following outcome with no infinite loop: f-0 (MAIN::initial-fact) f-1 (MAIN::D (A 1) (B nil)) For a total of 2 facts in module MAIN. f-0 (MAIN::initial-fact) f-1 (MAIN::D (A 1) (B 3)) For a total of 2 facts in module MAIN. It seems slot-specific makes no difference in the outcome. I suspect I am missing a key concept here. Could someone explain? Thanks. Felix -------------------------------------------------------------------- To unsubscribe, send the words 'unsubscribe jess-users y...@address.com' in the BODY of a message to majord...@sandia.gov, NOT to the list (use your own address!) List problems? Notify owner-jess-us...@sandia.gov. --------------------------------------------------------------------
