A novel approach is proposed for ezpresaing and computing eficienily a large cla88 of problem8, including jinding the shortest path in a graph, that were previously considered impervious to an efiient treatment in the declarative framework of logic-baaed languageu. Our approach w based on the u8e of ruin and nmx predicate having a jht-order semantica defined using mleu w“th negation in their bodien. We show that when certain monotonicity condition8 hold then (1) there ezists a total well-founded model for these progmrnn containing negation, (2) this model can be computed eflciently using a procedure called greedy fixpoint, and (3) the original program can be rewritten into a more eficient one by puuhing rnin and max predicate8 into recursion. The greedy jizpoint evaluation of the program expressing the shorted path problem coincideu with Dijkdra’s algon”thm.
['Sumit Ganguly', 'Sergio Greco', 'Carlo Zaniolo']
Minimum and maximum predicates in logic programming