YES We show the termination of the TRS R: p(a(x0),p(b(x1),p(a(x2),x3))) -> p(x2,p(a(a(x0)),p(b(x1),x3))) -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(x2,p(a(a(x0)),p(b(x1),x3))) p2: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(a(a(x0)),p(b(x1),x3)) p3: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(b(x1),x3) and R consists of: r1: p(a(x0),p(b(x1),p(a(x2),x3))) -> p(x2,p(a(a(x0)),p(b(x1),x3))) The estimated dependency graph contains the following SCCs: {p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: p#(a(x0),p(b(x1),p(a(x2),x3))) -> p#(a(a(x0)),p(b(x1),x3)) and R consists of: r1: p(a(x0),p(b(x1),p(a(x2),x3))) -> p(x2,p(a(a(x0)),p(b(x1),x3))) The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^3 order: lexicographic order interpretations: p#_A(x1,x2) = ((0,0,0),(1,0,0),(1,0,0)) x2 a_A(x1) = ((1,0,0),(0,0,0),(1,1,0)) x1 + (1,1,1) p_A(x1,x2) = ((1,0,0),(1,1,0),(0,0,1)) x1 + ((1,0,0),(1,0,0),(0,0,0)) x2 b_A(x1) = ((1,0,0),(0,1,0),(0,1,1)) x1 + (1,1,1) 2. lexicographic path order with precedence: precedence: p# > b > p > a argument filter: pi(p#) = [] pi(a) = [] pi(p) = [] pi(b) = [1] The next rules are strictly ordered: p1 We remove them from the problem. Then no dependency pair remains.