YES Consider the TRS R consisting of the following rewrite rules: f(j(x,y),y) -> g(f(x,k(y))) f(x,h1(y,z)) -> h2(0,x,h1(y,z)) g(h2(x,y,h1(z,u))) -> h2(s(x),y,h1(z,u)) h2(x,j(y,h1(z,u)),h1(z,u)) -> h2(s(x),y,h1(s(z),u)) i(f(x,h(y))) -> y i(h2(s(x),y,h1(x,z))) -> z k(h(x)) -> h1(0,x) k(h1(x,y)) -> h1(s(x),y) The TRS R is transformed (by dropping rewrite rules whose left-hand sides contain a function symbol which does not occur in any right-hand side) into a TRS R' which is empty. Hence R is terminating. __________________________________________________________________ TTTbox (0.005 seconds) - April 13, 2007 Source file - /home/ami/mkorp/Testbench/tpdb-3.2/TRS/SK90/2.61.trs