YES (ignored inputs)COMMENT from the collection of \cite{AT2012} Rewrite Rules: [ f(0,0) -> f(0,1), f(1,0) -> f(0,0), f(?x,?y) -> f(?y,?x) ] Apply Direct Methods... Inner CPs: [ ] Outer CPs: [ f(0,1) = f(0,0), f(0,0) = f(0,1) ] Overlay, check Innermost Termination... unknown Innermost Terminating unknown Knuth & Bendix Linear Development Closed Direct Methods: CR Final result: CR 150.trs: Success(CR) (0 msec.)