YES # Compositional parallel rule labeling (Shintani and Hirokawa 2022). Consider the left-linear TRS R: +(0(),y) -> y +(x,0()) -> x +(s(x),y) -> s(+(y,x)) +(x,s(y)) -> s(+(x,y)) +(x,+(y,z)) -> +(+(x,y),z) +(x,y) -> +(y,x) Let C be the following subset of R: (empty) All parallel critical peaks (except C's) are decreasing wrt rule labeling: phi(+(0(),y) -> y) = 2 phi(+(x,0()) -> x) = 1 phi(+(s(x),y) -> s(+(y,x))) = 7 phi(+(x,s(y)) -> s(+(x,y))) = 7 phi(+(x,+(y,z)) -> +(+(x,y),z)) = 11 phi(+(x,y) -> +(y,x)) = 9 psi(+(0(),y) -> y) = 6 psi(+(x,0()) -> x) = 5 psi(+(s(x),y) -> s(+(y,x))) = 3 psi(+(x,s(y)) -> s(+(x,y))) = 8 psi(+(x,+(y,z)) -> +(+(x,y),z)) = 10 psi(+(x,y) -> +(y,x)) = 4 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.