YES O(n^4) TRS: { a__h(X) -> h(X), a__h(d()) -> a__g(c()), a__g(X) -> a__h(X), a__g(X) -> g(X), a__c() -> d(), a__c() -> c(), mark(d()) -> d(), mark(c()) -> a__c(), mark(g(X)) -> a__g(X), mark(h(X)) -> a__h(X) } DUP: We consider a non-duplicating system. Trs: { a__h(X) -> h(X), a__h(d()) -> a__g(c()), a__g(X) -> a__h(X), a__g(X) -> g(X), a__c() -> d(), a__c() -> c(), mark(d()) -> d(), mark(c()) -> a__c(), mark(g(X)) -> a__g(X), mark(h(X)) -> a__h(X) } Matrix Interpretation: Interpretation class: triangular [X3] [1 3 0 0][X3] [0] [X2] [0 0 3 0][X2] [0] [h]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 3 0 0][X3] [0] [X2] [0 0 3 0][X2] [0] [g]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [0] [X3] [1 3 0 0][X3] [3] [X2] [0 1 0 0][X2] [2] [mark]([X1]) = [0 0 0 0][X1] + [2] [X0] [0 0 0 0][X0] [2] [0] [0] [c] = [0] [0] [2] [2] [a__c] = [2] [1] [1] [1] [d] = [0] [0] [X3] [1 3 0 0][X3] [2] [X2] [0 0 3 0][X2] [0] [a__g]([X1]) = [0 0 0 0][X1] + [2] [X0] [0 0 0 0][X0] [1] [X3] [1 3 0 0][X3] [1] [X2] [0 0 3 0][X2] [0] [a__h]([X1]) = [0 0 0 0][X1] + [2] [X0] [0 0 0 0][X0] [1] Qed