YES We show the termination of the TRS R: a__g(X) -> a__h(X) a__c() -> d() a__h(d()) -> a__g(c()) mark(g(X)) -> a__g(X) mark(h(X)) -> a__h(X) mark(c()) -> a__c() mark(d()) -> d() a__g(X) -> g(X) a__h(X) -> h(X) a__c() -> c() -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: a__g#(X) -> a__h#(X) p2: a__h#(d()) -> a__g#(c()) p3: mark#(g(X)) -> a__g#(X) p4: mark#(h(X)) -> a__h#(X) p5: mark#(c()) -> a__c#() and R consists of: r1: a__g(X) -> a__h(X) r2: a__c() -> d() r3: a__h(d()) -> a__g(c()) r4: mark(g(X)) -> a__g(X) r5: mark(h(X)) -> a__h(X) r6: mark(c()) -> a__c() r7: mark(d()) -> d() r8: a__g(X) -> g(X) r9: a__h(X) -> h(X) r10: a__c() -> c() The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: a__g#(X) -> a__h#(X) p2: a__h#(d()) -> a__g#(c()) and R consists of: r1: a__g(X) -> a__h(X) r2: a__c() -> d() r3: a__h(d()) -> a__g(c()) r4: mark(g(X)) -> a__g(X) r5: mark(h(X)) -> a__h(X) r6: mark(c()) -> a__c() r7: mark(d()) -> d() r8: a__g(X) -> g(X) r9: a__h(X) -> h(X) r10: a__c() -> c() The set of usable rules consists of (no rules) Take the monotone reduction pair: lexicographic combination of reduction pairs: 1. weighted path order base order: max/plus interpretations on natural numbers: a__g#_A(x1) = max{7, x1 + 2} a__h#_A(x1) = max{3, x1 + 2} d_A = 5 c_A = 4 precedence: a__g# = a__h# = d = c partial status: pi(a__g#) = [1] pi(a__h#) = [1] pi(d) = [] pi(c) = [] 2. weighted path order base order: max/plus interpretations on natural numbers: a__g#_A(x1) = max{4, x1 + 2} a__h#_A(x1) = max{1, x1} d_A = 3 c_A = 2 precedence: a__g# = a__h# = d = c partial status: pi(a__g#) = [1] pi(a__h#) = [1] pi(d) = [] pi(c) = [] The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.