YES TRS: sum(0()) -> 0() sum(s(x)) -> +(sum(x),s(x)) +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) linear polynomial interpretations on N: sum_A(x1) = x1 + 1 sum#_A(x1) = x1 + 3 0_A = 1 0#_A = 0 s_A(x1) = x1 s#_A(x1) = 0 +_A(x1,x2) = x1 +#_A(x1,x2) = x1 + 1 precedence: sum > + > 0 = s