YES Problem: f(x,y) -> h(x,y) f(x,y) -> h(y,x) h(x,x) -> x Proof: Bounds Processor: bound: 0 enrichment: roof automaton: final states: {3,2,1} transitions: h0(3,3) -> 1* h0(2,3) -> 1* h0(3,2) -> 1* h0(2,2) -> 1* f20() -> 3*,1,2 2 -> 1* 3 -> 1* problem: Qed