%= save compiled clauses using forward chaining storage (by default) %= we are using forward chaining just so any logical errors, performance and program bugs manefest %= immediately :- use_module(library(pfc)). :- set_clause_compile(fwc). %= Dont Trace execution make_ex_some(Var,Statement,AltStatement):- copy_term(Var+Statement,AltVar+AltStatement), AltVar = ex(Var,Statement). ( (ex_some(Var,Statement)/ make_ex_some(Var,Statement,AltStatement)) ==> (\+ Statement ==> AltStatement)). :- mpred_trace_exec. person(C) ==> ex_some(P,bio_father(C,P)). person(C) ==> ex_some(P,bio_mother(C,P)). person(joe). male(P) ==> ~female(P). female(P) ==> ~male(P). bio_mother(C,P) <==> (bio_parent(C,P) , female(P)). bio_father(C,P) <==> (bio_parent(C,P) , male(P)). bio_mother(douglas,eileen). pos_neg_proofs(P) :- mpred_why(P), mpred_why(~P). person(douglas).