YES We show the termination of the TRS R: a(f(),a(f(),x)) -> a(x,x) a(h(),x) -> a(f(),a(g(),a(f(),x))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: a#(f(),a(f(),x)) -> a#(x,x) p2: a#(h(),x) -> a#(f(),a(g(),a(f(),x))) p3: a#(h(),x) -> a#(g(),a(f(),x)) p4: a#(h(),x) -> a#(f(),x) and R consists of: r1: a(f(),a(f(),x)) -> a(x,x) r2: a(h(),x) -> a(f(),a(g(),a(f(),x))) The estimated dependency graph contains the following SCCs: {p1, p4} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: a#(f(),a(f(),x)) -> a#(x,x) p2: a#(h(),x) -> a#(f(),x) and R consists of: r1: a(f(),a(f(),x)) -> a(x,x) r2: a(h(),x) -> a(f(),a(g(),a(f(),x))) The set of usable rules consists of (no rules) Take the reduction pair: matrix interpretations: carrier: N^4 order: lexicographic order interpretations: a#_A(x1,x2) = ((0,0,0,0),(0,0,0,0),(0,0,0,0),(1,0,0,0)) x2 f_A() = (1,1,1,1) a_A(x1,x2) = ((1,0,0,0),(0,1,0,0),(1,0,1,0),(0,0,0,0)) x1 + ((1,0,0,0),(1,0,0,0),(0,1,0,0),(1,1,1,0)) x2 + (0,0,0,1) h_A() = (2,1,1,1) The next rules are strictly ordered: p1 We remove them from the problem. -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: a#(h(),x) -> a#(f(),x) and R consists of: r1: a(f(),a(f(),x)) -> a(x,x) r2: a(h(),x) -> a(f(),a(g(),a(f(),x))) The estimated dependency graph contains the following SCCs: (no SCCs)