/export/starexec/sandbox/solver/bin/starexec_run_standard /export/starexec/sandbox/benchmark/theBenchmark.xml /export/starexec/sandbox/output/output_files -------------------------------------------------------------------------------- YES proof of /export/starexec/sandbox/benchmark/theBenchmark.xml # AProVE Commit ID: 48fb2092695e11cc9f56e44b17a92a5f88ffb256 marcel 20180622 unpublished dirty Termination w.r.t. Q of the given QTRS could be proven: (0) QTRS (1) Overlay + Local Confluence [EQUIVALENT, 0 ms] (2) QTRS (3) DependencyPairsProof [EQUIVALENT, 25 ms] (4) QDP (5) DependencyGraphProof [EQUIVALENT, 0 ms] (6) AND (7) QDP (8) UsableRulesProof [EQUIVALENT, 0 ms] (9) QDP (10) QReductionProof [EQUIVALENT, 0 ms] (11) QDP (12) QDPSizeChangeProof [EQUIVALENT, 0 ms] (13) YES (14) QDP (15) QDPOrderProof [EQUIVALENT, 67 ms] (16) QDP (17) PisEmptyProof [EQUIVALENT, 0 ms] (18) YES ---------------------------------------- (0) Obligation: Q restricted rewrite system: The TRS R consists of the following rules: and(false, false) -> false and(true, false) -> false and(false, true) -> false and(true, true) -> true eq(nil, nil) -> true eq(cons(T, L), nil) -> false eq(nil, cons(T, L)) -> false eq(cons(T, L), cons(Tp, Lp)) -> and(eq(T, Tp), eq(L, Lp)) eq(var(L), var(Lp)) -> eq(L, Lp) eq(var(L), apply(T, S)) -> false eq(var(L), lambda(X, T)) -> false eq(apply(T, S), var(L)) -> false eq(apply(T, S), apply(Tp, Sp)) -> and(eq(T, Tp), eq(S, Sp)) eq(apply(T, S), lambda(X, Tp)) -> false eq(lambda(X, T), var(L)) -> false eq(lambda(X, T), apply(Tp, Sp)) -> false eq(lambda(X, T), lambda(Xp, Tp)) -> and(eq(T, Tp), eq(X, Xp)) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) Q is empty. ---------------------------------------- (1) Overlay + Local Confluence (EQUIVALENT) The TRS is overlay and locally confluent. By [NOC] we can switch to innermost. ---------------------------------------- (2) Obligation: Q restricted rewrite system: The TRS R consists of the following rules: and(false, false) -> false and(true, false) -> false and(false, true) -> false and(true, true) -> true eq(nil, nil) -> true eq(cons(T, L), nil) -> false eq(nil, cons(T, L)) -> false eq(cons(T, L), cons(Tp, Lp)) -> and(eq(T, Tp), eq(L, Lp)) eq(var(L), var(Lp)) -> eq(L, Lp) eq(var(L), apply(T, S)) -> false eq(var(L), lambda(X, T)) -> false eq(apply(T, S), var(L)) -> false eq(apply(T, S), apply(Tp, Sp)) -> and(eq(T, Tp), eq(S, Sp)) eq(apply(T, S), lambda(X, Tp)) -> false eq(lambda(X, T), var(L)) -> false eq(lambda(X, T), apply(Tp, Sp)) -> false eq(lambda(X, T), lambda(Xp, Tp)) -> and(eq(T, Tp), eq(X, Xp)) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) The set Q consists of the following terms: and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) ---------------------------------------- (3) DependencyPairsProof (EQUIVALENT) Using Dependency Pairs [AG00,LPAR04] we result in the following initial DP problem. ---------------------------------------- (4) Obligation: Q DP problem: The TRS P consists of the following rules: EQ(cons(T, L), cons(Tp, Lp)) -> AND(eq(T, Tp), eq(L, Lp)) EQ(cons(T, L), cons(Tp, Lp)) -> EQ(T, Tp) EQ(cons(T, L), cons(Tp, Lp)) -> EQ(L, Lp) EQ(var(L), var(Lp)) -> EQ(L, Lp) EQ(apply(T, S), apply(Tp, Sp)) -> AND(eq(T, Tp), eq(S, Sp)) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(T, Tp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(S, Sp) EQ(lambda(X, T), lambda(Xp, Tp)) -> AND(eq(T, Tp), eq(X, Xp)) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(T, Tp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(X, Xp) REN(var(L), var(K), var(Lp)) -> IF(eq(L, Lp), var(K), var(Lp)) REN(var(L), var(K), var(Lp)) -> EQ(L, Lp) REN(X, Y, apply(T, S)) -> REN(X, Y, T) REN(X, Y, apply(T, S)) -> REN(X, Y, S) REN(X, Y, lambda(Z, T)) -> REN(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T)) REN(X, Y, lambda(Z, T)) -> REN(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T) The TRS R consists of the following rules: and(false, false) -> false and(true, false) -> false and(false, true) -> false and(true, true) -> true eq(nil, nil) -> true eq(cons(T, L), nil) -> false eq(nil, cons(T, L)) -> false eq(cons(T, L), cons(Tp, Lp)) -> and(eq(T, Tp), eq(L, Lp)) eq(var(L), var(Lp)) -> eq(L, Lp) eq(var(L), apply(T, S)) -> false eq(var(L), lambda(X, T)) -> false eq(apply(T, S), var(L)) -> false eq(apply(T, S), apply(Tp, Sp)) -> and(eq(T, Tp), eq(S, Sp)) eq(apply(T, S), lambda(X, Tp)) -> false eq(lambda(X, T), var(L)) -> false eq(lambda(X, T), apply(Tp, Sp)) -> false eq(lambda(X, T), lambda(Xp, Tp)) -> and(eq(T, Tp), eq(X, Xp)) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) The set Q consists of the following terms: and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) We have to consider all minimal (P,Q,R)-chains. ---------------------------------------- (5) DependencyGraphProof (EQUIVALENT) The approximation of the Dependency Graph [LPAR04,FROCOS05,EDGSTAR] contains 2 SCCs with 5 less nodes. ---------------------------------------- (6) Complex Obligation (AND) ---------------------------------------- (7) Obligation: Q DP problem: The TRS P consists of the following rules: EQ(cons(T, L), cons(Tp, Lp)) -> EQ(L, Lp) EQ(cons(T, L), cons(Tp, Lp)) -> EQ(T, Tp) EQ(var(L), var(Lp)) -> EQ(L, Lp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(T, Tp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(S, Sp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(T, Tp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(X, Xp) The TRS R consists of the following rules: and(false, false) -> false and(true, false) -> false and(false, true) -> false and(true, true) -> true eq(nil, nil) -> true eq(cons(T, L), nil) -> false eq(nil, cons(T, L)) -> false eq(cons(T, L), cons(Tp, Lp)) -> and(eq(T, Tp), eq(L, Lp)) eq(var(L), var(Lp)) -> eq(L, Lp) eq(var(L), apply(T, S)) -> false eq(var(L), lambda(X, T)) -> false eq(apply(T, S), var(L)) -> false eq(apply(T, S), apply(Tp, Sp)) -> and(eq(T, Tp), eq(S, Sp)) eq(apply(T, S), lambda(X, Tp)) -> false eq(lambda(X, T), var(L)) -> false eq(lambda(X, T), apply(Tp, Sp)) -> false eq(lambda(X, T), lambda(Xp, Tp)) -> and(eq(T, Tp), eq(X, Xp)) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) The set Q consists of the following terms: and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) We have to consider all minimal (P,Q,R)-chains. ---------------------------------------- (8) UsableRulesProof (EQUIVALENT) As all Q-normal forms are R-normal forms we are in the innermost case. Hence, by the usable rules processor [LPAR04] we can delete all non-usable rules [FROCOS05] from R. ---------------------------------------- (9) Obligation: Q DP problem: The TRS P consists of the following rules: EQ(cons(T, L), cons(Tp, Lp)) -> EQ(L, Lp) EQ(cons(T, L), cons(Tp, Lp)) -> EQ(T, Tp) EQ(var(L), var(Lp)) -> EQ(L, Lp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(T, Tp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(S, Sp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(T, Tp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(X, Xp) R is empty. The set Q consists of the following terms: and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) We have to consider all minimal (P,Q,R)-chains. ---------------------------------------- (10) QReductionProof (EQUIVALENT) We deleted the following terms from Q as each root-symbol of these terms does neither occur in P nor in R.[THIEMANN]. and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) ---------------------------------------- (11) Obligation: Q DP problem: The TRS P consists of the following rules: EQ(cons(T, L), cons(Tp, Lp)) -> EQ(L, Lp) EQ(cons(T, L), cons(Tp, Lp)) -> EQ(T, Tp) EQ(var(L), var(Lp)) -> EQ(L, Lp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(T, Tp) EQ(apply(T, S), apply(Tp, Sp)) -> EQ(S, Sp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(T, Tp) EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(X, Xp) R is empty. Q is empty. We have to consider all minimal (P,Q,R)-chains. ---------------------------------------- (12) QDPSizeChangeProof (EQUIVALENT) By using the subterm criterion [SUBTERM_CRITERION] together with the size-change analysis [AAECC05] we have proven that there are no infinite chains for this DP problem. From the DPs we obtained the following set of size-change graphs: *EQ(cons(T, L), cons(Tp, Lp)) -> EQ(L, Lp) The graph contains the following edges 1 > 1, 2 > 2 *EQ(cons(T, L), cons(Tp, Lp)) -> EQ(T, Tp) The graph contains the following edges 1 > 1, 2 > 2 *EQ(var(L), var(Lp)) -> EQ(L, Lp) The graph contains the following edges 1 > 1, 2 > 2 *EQ(apply(T, S), apply(Tp, Sp)) -> EQ(T, Tp) The graph contains the following edges 1 > 1, 2 > 2 *EQ(apply(T, S), apply(Tp, Sp)) -> EQ(S, Sp) The graph contains the following edges 1 > 1, 2 > 2 *EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(T, Tp) The graph contains the following edges 1 > 1, 2 > 2 *EQ(lambda(X, T), lambda(Xp, Tp)) -> EQ(X, Xp) The graph contains the following edges 1 > 1, 2 > 2 ---------------------------------------- (13) YES ---------------------------------------- (14) Obligation: Q DP problem: The TRS P consists of the following rules: REN(X, Y, apply(T, S)) -> REN(X, Y, S) REN(X, Y, apply(T, S)) -> REN(X, Y, T) REN(X, Y, lambda(Z, T)) -> REN(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T)) REN(X, Y, lambda(Z, T)) -> REN(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T) The TRS R consists of the following rules: and(false, false) -> false and(true, false) -> false and(false, true) -> false and(true, true) -> true eq(nil, nil) -> true eq(cons(T, L), nil) -> false eq(nil, cons(T, L)) -> false eq(cons(T, L), cons(Tp, Lp)) -> and(eq(T, Tp), eq(L, Lp)) eq(var(L), var(Lp)) -> eq(L, Lp) eq(var(L), apply(T, S)) -> false eq(var(L), lambda(X, T)) -> false eq(apply(T, S), var(L)) -> false eq(apply(T, S), apply(Tp, Sp)) -> and(eq(T, Tp), eq(S, Sp)) eq(apply(T, S), lambda(X, Tp)) -> false eq(lambda(X, T), var(L)) -> false eq(lambda(X, T), apply(Tp, Sp)) -> false eq(lambda(X, T), lambda(Xp, Tp)) -> and(eq(T, Tp), eq(X, Xp)) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) The set Q consists of the following terms: and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) We have to consider all minimal (P,Q,R)-chains. ---------------------------------------- (15) QDPOrderProof (EQUIVALENT) We use the reduction pair processor [LPAR04,JAR06]. The following pairs can be oriented strictly and are deleted. REN(X, Y, apply(T, S)) -> REN(X, Y, S) REN(X, Y, apply(T, S)) -> REN(X, Y, T) REN(X, Y, lambda(Z, T)) -> REN(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T)) REN(X, Y, lambda(Z, T)) -> REN(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T) The remaining pairs can at least be oriented weakly. Used ordering: Combined order from the following AFS and order. REN(x1, x2, x3) = x3 apply(x1, x2) = apply(x1, x2) lambda(x1, x2) = lambda(x2) ren(x1, x2, x3) = ren(x3) var(x1) = var if(x1, x2, x3) = if Knuth-Bendix order [KBO] with precedence:ren_1 > lambda_1 ren_1 > if > var ren_1 > apply_2 and weight map: lambda_1=1 var=1 ren_1=0 apply_2=1 if=1 The following usable rules [FROCOS05] with respect to the argument filtering of the ordering [JAR06] were oriented: ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ---------------------------------------- (16) Obligation: Q DP problem: P is empty. The TRS R consists of the following rules: and(false, false) -> false and(true, false) -> false and(false, true) -> false and(true, true) -> true eq(nil, nil) -> true eq(cons(T, L), nil) -> false eq(nil, cons(T, L)) -> false eq(cons(T, L), cons(Tp, Lp)) -> and(eq(T, Tp), eq(L, Lp)) eq(var(L), var(Lp)) -> eq(L, Lp) eq(var(L), apply(T, S)) -> false eq(var(L), lambda(X, T)) -> false eq(apply(T, S), var(L)) -> false eq(apply(T, S), apply(Tp, Sp)) -> and(eq(T, Tp), eq(S, Sp)) eq(apply(T, S), lambda(X, Tp)) -> false eq(lambda(X, T), var(L)) -> false eq(lambda(X, T), apply(Tp, Sp)) -> false eq(lambda(X, T), lambda(Xp, Tp)) -> and(eq(T, Tp), eq(X, Xp)) if(true, var(K), var(L)) -> var(K) if(false, var(K), var(L)) -> var(L) ren(var(L), var(K), var(Lp)) -> if(eq(L, Lp), var(K), var(Lp)) ren(X, Y, apply(T, S)) -> apply(ren(X, Y, T), ren(X, Y, S)) ren(X, Y, lambda(Z, T)) -> lambda(var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), ren(X, Y, ren(Z, var(cons(X, cons(Y, cons(lambda(Z, T), nil)))), T))) The set Q consists of the following terms: and(false, false) and(true, false) and(false, true) and(true, true) eq(nil, nil) eq(cons(x0, x1), nil) eq(nil, cons(x0, x1)) eq(cons(x0, x1), cons(x2, x3)) eq(var(x0), var(x1)) eq(var(x0), apply(x1, x2)) eq(var(x0), lambda(x1, x2)) eq(apply(x0, x1), var(x2)) eq(apply(x0, x1), apply(x2, x3)) eq(apply(x0, x1), lambda(x2, x3)) eq(lambda(x0, x1), var(x2)) eq(lambda(x0, x1), apply(x2, x3)) eq(lambda(x0, x1), lambda(x2, x3)) if(true, var(x0), var(x1)) if(false, var(x0), var(x1)) ren(var(x0), var(x1), var(x2)) ren(x0, x1, apply(x2, x3)) ren(x0, x1, lambda(x2, x3)) We have to consider all minimal (P,Q,R)-chains. ---------------------------------------- (17) PisEmptyProof (EQUIVALENT) The TRS P is empty. Hence, there is no (P,Q,R) chain. ---------------------------------------- (18) YES