YES # Compositional parallel rule labeling (Shintani and Hirokawa 2022). Consider the left-linear TRS R: E(+(x,y)) -> *(E(x),E(y)) E(0()) -> 1() +(x,0()) -> x +(0(),x) -> x *(x,1()) -> x *(1(),x) -> x +(+(x,y),z) -> +(x,+(y,z)) +(x,+(y,z)) -> +(+(x,y),z) +(x,y) -> +(y,x) *(*(x,y),z) -> *(x,*(y,z)) *(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(E(+(x,y)) -> *(E(x),E(y))) = 13 phi(E(0()) -> 1()) = 3 phi(+(x,0()) -> x) = 17 phi(+(0(),x) -> x) = 16 phi(*(x,1()) -> x) = 6 phi(*(1(),x) -> x) = 5 phi(+(+(x,y),z) -> +(x,+(y,z))) = 13 phi(+(x,+(y,z)) -> +(+(x,y),z)) = 14 phi(+(x,y) -> +(y,x)) = 13 phi(*(*(x,y),z) -> *(x,*(y,z))) = 11 phi(*(x,*(y,z)) -> *(*(x,y),z)) = 11 phi(*(x,y) -> *(y,x)) = 12 psi(E(+(x,y)) -> *(E(x),E(y))) = 7 psi(E(0()) -> 1()) = 1 psi(+(x,0()) -> x) = 12 psi(+(0(),x) -> x) = 11 psi(*(x,1()) -> x) = 9 psi(*(1(),x) -> x) = 10 psi(+(+(x,y),z) -> +(x,+(y,z))) = 15 psi(+(x,+(y,z)) -> +(+(x,y),z)) = 18 psi(+(x,y) -> +(y,x)) = 15 psi(*(*(x,y),z) -> *(x,*(y,z))) = 9 psi(*(x,*(y,z)) -> *(*(x,y),z)) = 8 psi(*(x,y) -> *(y,x)) = 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.