MAYBE MAYBE TRS: { __(X1, mark(X2)) -> mark(__(X1, X2)), __(mark(X1), X2) -> mark(__(X1, X2)), __(ok(X1), ok(X2)) -> ok(__(X1, X2)), active(__(X, nil())) -> mark(X), active(__(X1, X2)) -> __(X1, active(X2)), active(__(X1, X2)) -> __(active(X1), X2), active(__(__(X, Y), Z)) -> mark(__(X, __(Y, Z))), active(__(nil(), X)) -> mark(X), active(and(X1, X2)) -> and(active(X1), X2), active(and(tt(), X)) -> mark(X), active(isNePal(X)) -> isNePal(active(X)), active(isNePal(__(I, __(P, I)))) -> mark(tt()), and(mark(X1), X2) -> mark(and(X1, X2)), and(ok(X1), ok(X2)) -> ok(and(X1, X2)), isNePal(mark(X)) -> mark(isNePal(X)), isNePal(ok(X)) -> ok(isNePal(X)), proper(__(X1, X2)) -> __(proper(X1), proper(X2)), proper(nil()) -> ok(nil()), proper(and(X1, X2)) -> and(proper(X1), proper(X2)), proper(tt()) -> ok(tt()), proper(isNePal(X)) -> isNePal(proper(X)), top(mark(X)) -> top(proper(X)), top(ok(X)) -> top(active(X)) } DUP: We consider a non-duplicating system. Trs: { __(X1, mark(X2)) -> mark(__(X1, X2)), __(mark(X1), X2) -> mark(__(X1, X2)), __(ok(X1), ok(X2)) -> ok(__(X1, X2)), active(__(X, nil())) -> mark(X), active(__(X1, X2)) -> __(X1, active(X2)), active(__(X1, X2)) -> __(active(X1), X2), active(__(__(X, Y), Z)) -> mark(__(X, __(Y, Z))), active(__(nil(), X)) -> mark(X), active(and(X1, X2)) -> and(active(X1), X2), active(and(tt(), X)) -> mark(X), active(isNePal(X)) -> isNePal(active(X)), active(isNePal(__(I, __(P, I)))) -> mark(tt()), and(mark(X1), X2) -> mark(and(X1, X2)), and(ok(X1), ok(X2)) -> ok(and(X1, X2)), isNePal(mark(X)) -> mark(isNePal(X)), isNePal(ok(X)) -> ok(isNePal(X)), proper(__(X1, X2)) -> __(proper(X1), proper(X2)), proper(nil()) -> ok(nil()), proper(and(X1, X2)) -> and(proper(X1), proper(X2)), proper(tt()) -> ok(tt()), proper(isNePal(X)) -> isNePal(proper(X)), top(mark(X)) -> top(proper(X)), top(ok(X)) -> top(active(X)) } Fail