Rule attribute for adding inverse of consequence as rule condition ------------------------------------------------------------------ Key: DROOLS-365 URL: https://issues.jboss.org/browse/DROOLS-365 Project: Drools Issue Type: Feature Request Security Level: Public(Everyone can see) Affects Versions: 5.5.0.Final Reporter: Adar Dembo Assignee: Mark Proctor I have quite a few rules that look like this: {noformat} rule "if foo then bar" when Foo($a : a, $b : b) not Bar(a == $a, b == $b) then insert(new Bar($a, $b)); end {noformat} This is a fairly common pattern for me: a rule should not activate if the facts generated by its consequence were already asserted. It's a pattern I use extensively to generate linear (i.e. non-repeating) workflows. Ideally I'd be able to express it as follows: {noformat} rule "if foo then bar" condition-on-inverse-of-consequence when Foo($a : a, $b : b) then insert(new Bar($a, $b)); end {noformat} And {{condition-on-inverse-of-consequence}} would cause Drools to generate the right kind of condition, which would be the inverse of the fact changes made by the consequence. I think {{lock-on-active}} is similar but harsher: it prevents the rule from firing a second time altogether, regardless of input. At least, that's based on my reading of the docs. In my example, that would be equivalent to {{not Bar()}} condition in the rule, which is stricter than {{not Bar(a == $a, b == $b)}}.