YES O(n^3) TRS: { app(app(plus(), app(s(), x)), y) -> app(s(), app(app(plus(), x), y)), app(id(), x) -> x, app(plus(), 0()) -> id() } DUP: We consider a non-duplicating system. Trs: { app(app(plus(), app(s(), x)), y) -> app(s(), app(app(plus(), x), y)), app(id(), x) -> x, app(plus(), 0()) -> id() } Matrix Interpretation: Interpretation class: triangular [0] [s] = [0] [0] [0] [0] = [0] [0] [0] [plus] = [0] [1] [0] [id] = [0] [0] [X5] [X2] [1 0 1][X5] [1 0 0][X2] [1] [app]([X4], [X1]) = [0 0 0][X4] + [0 1 0][X1] + [0] [X3] [X0] [0 0 1][X3] [0 0 1][X0] [1] Qed