NO Problem: +(0(),x) -> x +(-(x),x) -> 0() +(+(x,y),z) -> +(x,+(y,z)) +(x,y) -> +(y,x) -(0()) -> 0() -(-(x)) -> x -(+(x,y)) -> +(-(x),-(y)) *(1(),x) -> x *(x,+(y,z)) -> +(*(x,y),*(x,z)) *(*(x,y),z) -> *(x,*(y,z)) *(x,y) -> *(y,x) *(x,0()) -> 0() *(x,-(y)) -> -(*(x,y)) Proof: Containment Processor: loop length: 1 terms: +(x,y) context: [] substitution: x -> y y -> x Qed