1.65/0.76 YES 1.65/0.77 We consider the system theBenchmark. 1.65/0.77 1.65/0.77 Alphabet: 1.65/0.77 1.65/0.77 dom : [N * N * N] --> N 1.65/0.77 eval : [N * N] --> N 1.65/0.77 fun : [N -> N * N * N] --> N 1.65/0.77 o : [] --> N 1.65/0.77 s : [N] --> N 1.65/0.77 1.65/0.77 Rules: 1.65/0.77 1.65/0.77 eval(fun(f, x, y), z) => f dom(x, y, z) 1.65/0.77 dom(s(x), s(y), s(z)) => s(dom(x, y, z)) 1.65/0.77 dom(o, s(x), s(y)) => s(dom(o, x, y)) 1.65/0.77 dom(x, y, o) => x 1.65/0.77 dom(o, o, x) => o 1.65/0.77 1.65/0.77 This AFS is converted to an AFSM simply by replacing all free variables by meta-variables (with arity 0). 1.65/0.77 1.65/0.77 We observe that the rules contain a first-order subset: 1.65/0.77 1.65/0.77 dom(s(X), s(Y), s(Z)) => s(dom(X, Y, Z)) 1.65/0.77 dom(o, s(X), s(Y)) => s(dom(o, X, Y)) 1.65/0.77 dom(X, Y, o) => X 1.65/0.77 dom(o, o, X) => o 1.65/0.77 1.65/0.77 Moreover, the system is finitely branching. Thus, by [Kop12, Thm. 7.55], we may omit all first-order dependency pairs from the dependency pair problem (DP(R), R) if this first-order part is Ce-terminating when seen as a many-sorted first-order TRS. 1.65/0.77 1.65/0.77 According to the external first-order termination prover, this system is indeed Ce-terminating: 1.65/0.77 1.65/0.77 || proof of resources/system.trs 1.65/0.77 || # AProVE Commit ID: d84c10301d352dfd14de2104819581f4682260f5 fuhs 20130616 1.65/0.77 || 1.65/0.77 || 1.65/0.77 || Termination w.r.t. Q of the given QTRS could be proven: 1.65/0.77 || 1.65/0.77 || (0) QTRS 1.65/0.77 || (1) QTRSRRRProof [EQUIVALENT] 1.65/0.77 || (2) QTRS 1.65/0.77 || (3) RisEmptyProof [EQUIVALENT] 1.65/0.77 || (4) YES 1.65/0.77 || 1.65/0.77 || 1.65/0.77 || ---------------------------------------- 1.65/0.77 || 1.65/0.77 || (0) 1.65/0.77 || Obligation: 1.65/0.77 || Q restricted rewrite system: 1.65/0.77 || The TRS R consists of the following rules: 1.65/0.77 || 1.65/0.77 || dom(s(%X), s(%Y), s(%Z)) -> s(dom(%X, %Y, %Z)) 1.65/0.77 || dom(o, s(%X), s(%Y)) -> s(dom(o, %X, %Y)) 1.65/0.77 || dom(%X, %Y, o) -> %X 1.65/0.77 || dom(o, o, %X) -> o 1.65/0.77 || ~PAIR(%X, %Y) -> %X 1.65/0.77 || ~PAIR(%X, %Y) -> %Y 1.65/0.77 || 1.65/0.77 || Q is empty. 1.65/0.77 || 1.65/0.77 || ---------------------------------------- 1.65/0.77 || 1.65/0.77 || (1) QTRSRRRProof (EQUIVALENT) 1.65/0.77 || Used ordering: 1.65/0.77 || Polynomial interpretation [POLO]: 1.65/0.77 || 1.65/0.77 || POL(dom(x_1, x_2, x_3)) = 1 + 2*x_1 + 2*x_2 + x_3 1.65/0.77 || POL(o) = 2 1.65/0.77 || POL(s(x_1)) = 1 + x_1 1.65/0.77 || POL(~PAIR(x_1, x_2)) = 2 + x_1 + x_2 1.65/0.77 || With this ordering the following rules can be removed by the rule removal processor [LPAR04] because they are oriented strictly: 1.65/0.77 || 1.65/0.77 || dom(s(%X), s(%Y), s(%Z)) -> s(dom(%X, %Y, %Z)) 1.65/0.77 || dom(o, s(%X), s(%Y)) -> s(dom(o, %X, %Y)) 1.65/0.77 || dom(%X, %Y, o) -> %X 1.65/0.77 || dom(o, o, %X) -> o 1.65/0.77 || ~PAIR(%X, %Y) -> %X 1.65/0.77 || ~PAIR(%X, %Y) -> %Y 1.65/0.77 || 1.65/0.77 || 1.65/0.77 || 1.65/0.77 || 1.65/0.77 || ---------------------------------------- 1.65/0.77 || 1.65/0.77 || (2) 1.65/0.77 || Obligation: 1.65/0.77 || Q restricted rewrite system: 1.65/0.77 || R is empty. 1.65/0.77 || Q is empty. 1.65/0.77 || 1.65/0.77 || ---------------------------------------- 1.65/0.77 || 1.65/0.77 || (3) RisEmptyProof (EQUIVALENT) 1.65/0.77 || The TRS R is empty. Hence, termination is trivially proven. 1.65/0.77 || ---------------------------------------- 1.65/0.77 || 1.65/0.77 || (4) 1.65/0.77 || YES 1.65/0.77 || 1.65/0.77 We use the dependency pair framework as described in [Kop12, Ch. 6/7], with dynamic dependency pairs. 1.65/0.77 1.65/0.77 After applying [Kop12, Thm. 7.22] to denote collapsing dependency pairs in an extended form, we thus obtain the following dependency pair problem (P_0, R_0, minimal, formative): 1.65/0.77 1.65/0.77 Dependency Pairs P_0: 1.65/0.77 1.65/0.77 0] eval#(fun(F, X, Y), Z) =#> F(dom(X, Y, Z)) 1.65/0.77 1] eval#(fun(F, X, Y), Z) =#> dom#(X, Y, Z) 1.65/0.77 1.65/0.77 Rules R_0: 1.65/0.77 1.65/0.77 eval(fun(F, X, Y), Z) => F dom(X, Y, Z) 1.65/0.77 dom(s(X), s(Y), s(Z)) => s(dom(X, Y, Z)) 1.65/0.77 dom(o, s(X), s(Y)) => s(dom(o, X, Y)) 1.65/0.77 dom(X, Y, o) => X 1.65/0.77 dom(o, o, X) => o 1.65/0.77 1.65/0.77 Thus, the original system is terminating if (P_0, R_0, minimal, formative) is finite. 1.65/0.77 1.65/0.77 We consider the dependency pair problem (P_0, R_0, minimal, formative). 1.65/0.77 1.65/0.77 We place the elements of P in a dependency graph approximation G (see e.g. [Kop12, Thm. 7.27, 7.29], as follows: 1.65/0.77 1.65/0.77 * 0 : 0, 1 1.65/0.77 * 1 : 1.65/0.77 1.65/0.77 This graph has the following strongly connected components: 1.65/0.77 1.65/0.77 P_1: 1.65/0.77 1.65/0.77 eval#(fun(F, X, Y), Z) =#> F(dom(X, Y, Z)) 1.65/0.77 1.65/0.77 By [Kop12, Thm. 7.31], we may replace any dependency pair problem (P_0, R_0, m, f) by (P_1, R_0, m, f). 1.65/0.77 1.65/0.77 Thus, the original system is terminating if (P_1, R_0, minimal, formative) is finite. 1.65/0.77 1.65/0.77 We consider the dependency pair problem (P_1, R_0, minimal, formative). 1.65/0.77 1.65/0.77 The formative rules of (P_1, R_0) are R_1 ::= 1.65/0.77 1.65/0.77 eval(fun(F, X, Y), Z) => F dom(X, Y, Z) 1.65/0.77 dom(X, Y, o) => X 1.65/0.77 dom(o, o, X) => o 1.65/0.77 1.65/0.77 By [Kop12, Thm. 7.17], we may replace the dependency pair problem (P_1, R_0, minimal, formative) by (P_1, R_1, minimal, formative). 1.65/0.77 1.65/0.77 Thus, the original system is terminating if (P_1, R_1, minimal, formative) is finite. 1.65/0.77 1.65/0.77 We consider the dependency pair problem (P_1, R_1, minimal, formative). 1.65/0.77 1.65/0.77 We will use the reduction pair processor [Kop12, Thm. 7.16]. As the system is abstraction-simple and the formative flag is set, it suffices to find a tagged reduction pair [Kop12, Def. 6.70]. Thus, we must orient: 1.65/0.77 1.65/0.77 eval#(fun(F, X, Y), Z) >? F(dom(X, Y, Z)) 1.65/0.77 eval(fun(F, X, Y), Z) >= F dom(X, Y, Z) 1.65/0.77 dom(X, Y, o) >= X 1.65/0.77 dom(o, o, X) >= o 1.65/0.77 1.65/0.77 We orient these requirements with a polynomial interpretation in the natural numbers. 1.65/0.77 1.65/0.77 The following interpretation satisfies the requirements: 1.65/0.77 1.65/0.77 dom = \y0y1y2.y0 1.65/0.77 eval = \y0y1.3 + 3y0 1.65/0.77 eval# = \y0y1.3 + y0 1.65/0.77 fun = \G0y1y2.3 + y1 + G0(y1) 1.65/0.77 o = 0 1.65/0.77 1.65/0.77 Using this interpretation, the requirements translate to: 1.65/0.77 1.65/0.77 [[eval#(fun(_F0, _x1, _x2), _x3)]] = 6 + x1 + F0(x1) > F0(x1) = [[_F0(dom(_x1, _x2, _x3))]] 1.65/0.77 [[eval(fun(_F0, _x1, _x2), _x3)]] = 12 + 3x1 + 3F0(x1) >= max(x1, F0(x1)) = [[_F0 dom(_x1, _x2, _x3)]] 1.65/0.77 [[dom(_x0, _x1, o)]] = x0 >= x0 = [[_x0]] 1.65/0.77 [[dom(o, o, _x0)]] = 0 >= 0 = [[o]] 1.65/0.77 1.65/0.77 By the observations in [Kop12, Sec. 6.6], this reduction pair suffices; we may thus replace a dependency pair problem (P_1, R_1) by ({}, R_1). By the empty set processor [Kop12, Thm. 7.15] this problem may be immediately removed. 1.65/0.77 1.65/0.77 As all dependency pair problems were succesfully simplified with sound (and complete) processors until nothing remained, we conclude termination. 1.65/0.77 1.65/0.77 1.65/0.77 +++ Citations +++ 1.65/0.77 1.65/0.77 [Kop12] C. Kop. Higher Order Termination. PhD Thesis, 2012. 1.65/0.77 EOF