:- module(trigger_no_active_occurrence,[trigger_no_active_occurrence/0]). :- use_module(library(chr)). :- chr_constraint a/1, b/2. a(X) # ID , b(X,R) <=> R = 1 pragma passive(ID). trigger_no_active_occurrence :- a(X), X = 1, b(1,R), R == 1.