YES # Compositional parallel rule labeling (Shintani and Hirokawa 2022). Consider the left-linear TRS R: +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) +(0(),y) -> y +(s(x),y) -> s(+(x,y)) inc(x) -> s(x) +(x,y) -> +(y,x) inc(+(x,y)) -> +(inc(x),y) Let C be the following subset of R: (empty) All parallel critical peaks (except C's) are decreasing wrt rule labeling: phi(+(x,0()) -> x) = 4 phi(+(x,s(y)) -> s(+(x,y))) = 2 phi(+(0(),y) -> y) = 5 phi(+(s(x),y) -> s(+(x,y))) = 7 phi(inc(x) -> s(x)) = 3 phi(+(x,y) -> +(y,x)) = 3 phi(inc(+(x,y)) -> +(inc(x),y)) = 8 psi(+(x,0()) -> x) = 7 psi(+(x,s(y)) -> s(+(x,y))) = 6 psi(+(0(),y) -> y) = 7 psi(+(s(x),y) -> s(+(x,y))) = 6 psi(inc(x) -> s(x)) = 1 psi(+(x,y) -> +(y,x)) = 6 psi(inc(+(x,y)) -> +(inc(x),y)) = 8 Therefore, the confluence of R follows from that of C. # Compositional parallel critical pair system (Shintani and Hirokawa 2022). Consider the left-linear TRS R: (empty) Let C be the following subset of R: (empty) The parallel critical pair system PCPS(R,C) is: (empty) All pairs in PCP(R) are joinable and PCPS(R,C)/R is terminating. Therefore, the confluence of R follows from that of C. # emptiness The empty TRS is confluent.