MAYBE MAYBE TRS: { active(and(X1, X2)) -> and(active(X1), X2), active(and(tt(), X)) -> mark(X), active(plus(N, 0())) -> mark(N), active(plus(N, s(M))) -> mark(s(plus(N, M))), active(plus(X1, X2)) -> plus(X1, active(X2)), active(plus(X1, X2)) -> plus(active(X1), X2), active(s(X)) -> s(active(X)), active(x(N, 0())) -> mark(0()), active(x(N, s(M))) -> mark(plus(x(N, M), N)), active(x(X1, X2)) -> x(X1, active(X2)), active(x(X1, X2)) -> x(active(X1), X2), and(mark(X1), X2) -> mark(and(X1, X2)), and(ok(X1), ok(X2)) -> ok(and(X1, X2)), plus(X1, mark(X2)) -> mark(plus(X1, X2)), plus(mark(X1), X2) -> mark(plus(X1, X2)), plus(ok(X1), ok(X2)) -> ok(plus(X1, X2)), s(mark(X)) -> mark(s(X)), s(ok(X)) -> ok(s(X)), x(X1, mark(X2)) -> mark(x(X1, X2)), x(mark(X1), X2) -> mark(x(X1, X2)), x(ok(X1), ok(X2)) -> ok(x(X1, X2)), proper(and(X1, X2)) -> and(proper(X1), proper(X2)), proper(tt()) -> ok(tt()), proper(plus(X1, X2)) -> plus(proper(X1), proper(X2)), proper(0()) -> ok(0()), proper(s(X)) -> s(proper(X)), proper(x(X1, X2)) -> x(proper(X1), proper(X2)), top(mark(X)) -> top(proper(X)), top(ok(X)) -> top(active(X)) } DUP: We consider a duplicating system. Trs: { active(and(X1, X2)) -> and(active(X1), X2), active(and(tt(), X)) -> mark(X), active(plus(N, 0())) -> mark(N), active(plus(N, s(M))) -> mark(s(plus(N, M))), active(plus(X1, X2)) -> plus(X1, active(X2)), active(plus(X1, X2)) -> plus(active(X1), X2), active(s(X)) -> s(active(X)), active(x(N, 0())) -> mark(0()), active(x(N, s(M))) -> mark(plus(x(N, M), N)), active(x(X1, X2)) -> x(X1, active(X2)), active(x(X1, X2)) -> x(active(X1), X2), and(mark(X1), X2) -> mark(and(X1, X2)), and(ok(X1), ok(X2)) -> ok(and(X1, X2)), plus(X1, mark(X2)) -> mark(plus(X1, X2)), plus(mark(X1), X2) -> mark(plus(X1, X2)), plus(ok(X1), ok(X2)) -> ok(plus(X1, X2)), s(mark(X)) -> mark(s(X)), s(ok(X)) -> ok(s(X)), x(X1, mark(X2)) -> mark(x(X1, X2)), x(mark(X1), X2) -> mark(x(X1, X2)), x(ok(X1), ok(X2)) -> ok(x(X1, X2)), proper(and(X1, X2)) -> and(proper(X1), proper(X2)), proper(tt()) -> ok(tt()), proper(plus(X1, X2)) -> plus(proper(X1), proper(X2)), proper(0()) -> ok(0()), proper(s(X)) -> s(proper(X)), proper(x(X1, X2)) -> x(proper(X1), proper(X2)), top(mark(X)) -> top(proper(X)), top(ok(X)) -> top(active(X)) } Fail