Certification Problem

Input (TPDB SRS_Standard/Secret_06_SRS/secr7)

The rewrite relation of the following TRS is considered.

a(b(c(x1))) → c(b(a(a(c(b(x1)))))) (1)
a(x1) → x1 (2)
b(x1) → x1 (3)
c(x1) → x1 (4)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by matchbox @ termCOMP 2023)

1 Closure Under Flat Contexts

Using the flat contexts

{c(☐), b(☐), a(☐)}

We obtain the transformed TRS
c(a(b(c(x1)))) → c(c(b(a(a(c(b(x1))))))) (5)
c(a(x1)) → c(x1) (6)
c(b(x1)) → c(x1) (7)
c(c(x1)) → c(x1) (8)
b(a(b(c(x1)))) → b(c(b(a(a(c(b(x1))))))) (9)
b(a(x1)) → b(x1) (10)
b(b(x1)) → b(x1) (11)
b(c(x1)) → b(x1) (12)
a(a(b(c(x1)))) → a(c(b(a(a(c(b(x1))))))) (13)
a(a(x1)) → a(x1) (14)
a(b(x1)) → a(x1) (15)
a(c(x1)) → a(x1) (16)

1.1 Semantic Labeling

The following interpretations form a model of the rules.

As carrier we take the set {0,1,2}. Symbols are labeled by the interpretation of their arguments using the interpretations (modulo 3):

[c(x1)] = 3x1 + 0
[b(x1)] = 3x1 + 1
[a(x1)] = 3x1 + 2

We obtain the labeled TRS
a2(a1(b0(c2(x1)))) → a0(c1(b2(a2(a0(c1(b2(x1))))))) (17)
a2(a1(b0(c1(x1)))) → a0(c1(b2(a2(a0(c1(b1(x1))))))) (18)
a2(a1(b0(c0(x1)))) → a0(c1(b2(a2(a0(c1(b0(x1))))))) (19)
b2(a1(b0(c2(x1)))) → b0(c1(b2(a2(a0(c1(b2(x1))))))) (20)
b2(a1(b0(c1(x1)))) → b0(c1(b2(a2(a0(c1(b1(x1))))))) (21)
b2(a1(b0(c0(x1)))) → b0(c1(b2(a2(a0(c1(b0(x1))))))) (22)
c2(a1(b0(c2(x1)))) → c0(c1(b2(a2(a0(c1(b2(x1))))))) (23)
c2(a1(b0(c1(x1)))) → c0(c1(b2(a2(a0(c1(b1(x1))))))) (24)
c2(a1(b0(c0(x1)))) → c0(c1(b2(a2(a0(c1(b0(x1))))))) (25)
a2(a2(x1)) → a2(x1) (26)
a2(a1(x1)) → a1(x1) (27)
a2(a0(x1)) → a0(x1) (28)
b2(a2(x1)) → b2(x1) (29)
b2(a1(x1)) → b1(x1) (30)
b2(a0(x1)) → b0(x1) (31)
c2(a2(x1)) → c2(x1) (32)
c2(a1(x1)) → c1(x1) (33)
c2(a0(x1)) → c0(x1) (34)
a1(b2(x1)) → a2(x1) (35)
a1(b1(x1)) → a1(x1) (36)
a1(b0(x1)) → a0(x1) (37)
b1(b2(x1)) → b2(x1) (38)
b1(b1(x1)) → b1(x1) (39)
b1(b0(x1)) → b0(x1) (40)
c1(b2(x1)) → c2(x1) (41)
c1(b1(x1)) → c1(x1) (42)
c1(b0(x1)) → c0(x1) (43)
a0(c2(x1)) → a2(x1) (44)
a0(c1(x1)) → a1(x1) (45)
a0(c0(x1)) → a0(x1) (46)
b0(c2(x1)) → b2(x1) (47)
b0(c1(x1)) → b1(x1) (48)
b0(c0(x1)) → b0(x1) (49)
c0(c2(x1)) → c2(x1) (50)
c0(c1(x1)) → c1(x1) (51)
c0(c0(x1)) → c0(x1) (52)

1.1.1 Rule Removal

Using the matrix interpretations of dimension 1 with strict dimension 1 over the rationals with delta = 1
[c0(x1)] = x1 +
1
[c1(x1)] = x1 +
1
[c2(x1)] = x1 +
1
[b0(x1)] = x1 +
0
[b1(x1)] = x1 +
0
[b2(x1)] = x1 +
0
[a0(x1)] = x1 +
0
[a1(x1)] = x1 +
1
[a2(x1)] = x1 +
0
all of the following rules can be deleted.
b2(a1(x1)) → b1(x1) (30)
c2(a1(x1)) → c1(x1) (33)
a1(b2(x1)) → a2(x1) (35)
a1(b0(x1)) → a0(x1) (37)
a0(c2(x1)) → a2(x1) (44)
a0(c0(x1)) → a0(x1) (46)
b0(c2(x1)) → b2(x1) (47)
b0(c1(x1)) → b1(x1) (48)
b0(c0(x1)) → b0(x1) (49)
c0(c2(x1)) → c2(x1) (50)
c0(c1(x1)) → c1(x1) (51)
c0(c0(x1)) → c0(x1) (52)

1.1.1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
c1#(b1(x1)) → c1#(x1) (53)
c1#(b2(x1)) → c2#(x1) (54)
c2#(a1(b0(c0(x1)))) → c1#(b0(x1)) (55)
c2#(a1(b0(c0(x1)))) → c1#(b2(a2(a0(c1(b0(x1)))))) (56)
c2#(a1(b0(c0(x1)))) → b2#(a2(a0(c1(b0(x1))))) (57)
c2#(a1(b0(c0(x1)))) → a0#(c1(b0(x1))) (58)
c2#(a1(b0(c0(x1)))) → a2#(a0(c1(b0(x1)))) (59)
c2#(a1(b0(c1(x1)))) → c1#(b1(x1)) (60)
c2#(a1(b0(c1(x1)))) → c1#(b2(a2(a0(c1(b1(x1)))))) (61)
c2#(a1(b0(c1(x1)))) → b1#(x1) (62)
c2#(a1(b0(c1(x1)))) → b2#(a2(a0(c1(b1(x1))))) (63)
c2#(a1(b0(c1(x1)))) → a0#(c1(b1(x1))) (64)
c2#(a1(b0(c1(x1)))) → a2#(a0(c1(b1(x1)))) (65)
c2#(a1(b0(c2(x1)))) → c1#(b2(x1)) (66)
c2#(a1(b0(c2(x1)))) → c1#(b2(a2(a0(c1(b2(x1)))))) (67)
c2#(a1(b0(c2(x1)))) → b2#(x1) (68)
c2#(a1(b0(c2(x1)))) → b2#(a2(a0(c1(b2(x1))))) (69)
c2#(a1(b0(c2(x1)))) → a0#(c1(b2(x1))) (70)
c2#(a1(b0(c2(x1)))) → a2#(a0(c1(b2(x1)))) (71)
c2#(a2(x1)) → c2#(x1) (72)
b2#(a1(b0(c0(x1)))) → c1#(b0(x1)) (73)
b2#(a1(b0(c0(x1)))) → c1#(b2(a2(a0(c1(b0(x1)))))) (74)
b2#(a1(b0(c0(x1)))) → b2#(a2(a0(c1(b0(x1))))) (75)
b2#(a1(b0(c0(x1)))) → a0#(c1(b0(x1))) (76)
b2#(a1(b0(c0(x1)))) → a2#(a0(c1(b0(x1)))) (77)
b2#(a1(b0(c1(x1)))) → c1#(b1(x1)) (78)
b2#(a1(b0(c1(x1)))) → c1#(b2(a2(a0(c1(b1(x1)))))) (79)
b2#(a1(b0(c1(x1)))) → b1#(x1) (80)
b2#(a1(b0(c1(x1)))) → b2#(a2(a0(c1(b1(x1))))) (81)
b2#(a1(b0(c1(x1)))) → a0#(c1(b1(x1))) (82)
b2#(a1(b0(c1(x1)))) → a2#(a0(c1(b1(x1)))) (83)
b2#(a1(b0(c2(x1)))) → c1#(b2(x1)) (84)
b2#(a1(b0(c2(x1)))) → c1#(b2(a2(a0(c1(b2(x1)))))) (85)
b2#(a1(b0(c2(x1)))) → b2#(x1) (86)
b2#(a1(b0(c2(x1)))) → b2#(a2(a0(c1(b2(x1))))) (87)
b2#(a1(b0(c2(x1)))) → a0#(c1(b2(x1))) (88)
b2#(a1(b0(c2(x1)))) → a2#(a0(c1(b2(x1)))) (89)
b2#(a2(x1)) → b2#(x1) (90)
a0#(c1(x1)) → a1#(x1) (91)
a1#(b1(x1)) → a1#(x1) (92)
a2#(a1(b0(c0(x1)))) → c1#(b0(x1)) (93)
a2#(a1(b0(c0(x1)))) → c1#(b2(a2(a0(c1(b0(x1)))))) (94)
a2#(a1(b0(c0(x1)))) → b2#(a2(a0(c1(b0(x1))))) (95)
a2#(a1(b0(c0(x1)))) → a0#(c1(b0(x1))) (96)
a2#(a1(b0(c0(x1)))) → a0#(c1(b2(a2(a0(c1(b0(x1))))))) (97)
a2#(a1(b0(c0(x1)))) → a2#(a0(c1(b0(x1)))) (98)
a2#(a1(b0(c1(x1)))) → c1#(b1(x1)) (99)
a2#(a1(b0(c1(x1)))) → c1#(b2(a2(a0(c1(b1(x1)))))) (100)
a2#(a1(b0(c1(x1)))) → b1#(x1) (101)
a2#(a1(b0(c1(x1)))) → b2#(a2(a0(c1(b1(x1))))) (102)
a2#(a1(b0(c1(x1)))) → a0#(c1(b1(x1))) (103)
a2#(a1(b0(c1(x1)))) → a0#(c1(b2(a2(a0(c1(b1(x1))))))) (104)
a2#(a1(b0(c1(x1)))) → a2#(a0(c1(b1(x1)))) (105)
a2#(a1(b0(c2(x1)))) → c1#(b2(x1)) (106)
a2#(a1(b0(c2(x1)))) → c1#(b2(a2(a0(c1(b2(x1)))))) (107)
a2#(a1(b0(c2(x1)))) → b2#(x1) (108)
a2#(a1(b0(c2(x1)))) → b2#(a2(a0(c1(b2(x1))))) (109)
a2#(a1(b0(c2(x1)))) → a0#(c1(b2(x1))) (110)
a2#(a1(b0(c2(x1)))) → a0#(c1(b2(a2(a0(c1(b2(x1))))))) (111)
a2#(a1(b0(c2(x1)))) → a2#(a0(c1(b2(x1)))) (112)

1.1.1.1.1 Monotonic Reduction Pair Processor with Usable Rules

Using the matrix interpretations of dimension 1 with strict dimension 1 over the rationals with delta = 1
[c0(x1)] = x1 +
3
[c1(x1)] = x1 +
0
[c2(x1)] = x1 +
0
[b0(x1)] = x1 +
3
[b1(x1)] = x1 +
0
[b2(x1)] = x1 +
0
[a0(x1)] = x1 +
3
[a1(x1)] = x1 +
3
[a2(x1)] = x1 +
0
[c1#(x1)] = x1 +
2
[c2#(x1)] = x1 +
1
[b1#(x1)] = x1 +
0
[b2#(x1)] = x1 +
3
[a0#(x1)] = x1 +
2
[a1#(x1)] = x1 +
0
[a2#(x1)] = x1 +
3
together with the usable rules
a2(a1(b0(c2(x1)))) → a0(c1(b2(a2(a0(c1(b2(x1))))))) (17)
a2(a1(b0(c1(x1)))) → a0(c1(b2(a2(a0(c1(b1(x1))))))) (18)
a2(a1(b0(c0(x1)))) → a0(c1(b2(a2(a0(c1(b0(x1))))))) (19)
b2(a1(b0(c2(x1)))) → b0(c1(b2(a2(a0(c1(b2(x1))))))) (20)
b2(a1(b0(c1(x1)))) → b0(c1(b2(a2(a0(c1(b1(x1))))))) (21)
b2(a1(b0(c0(x1)))) → b0(c1(b2(a2(a0(c1(b0(x1))))))) (22)
c2(a1(b0(c2(x1)))) → c0(c1(b2(a2(a0(c1(b2(x1))))))) (23)
c2(a1(b0(c1(x1)))) → c0(c1(b2(a2(a0(c1(b1(x1))))))) (24)
c2(a1(b0(c0(x1)))) → c0(c1(b2(a2(a0(c1(b0(x1))))))) (25)
a2(a2(x1)) → a2(x1) (26)
a2(a1(x1)) → a1(x1) (27)
a2(a0(x1)) → a0(x1) (28)
b2(a2(x1)) → b2(x1) (29)
b2(a0(x1)) → b0(x1) (31)
c2(a2(x1)) → c2(x1) (32)
c2(a0(x1)) → c0(x1) (34)
a1(b1(x1)) → a1(x1) (36)
b1(b2(x1)) → b2(x1) (38)
b1(b1(x1)) → b1(x1) (39)
b1(b0(x1)) → b0(x1) (40)
c1(b2(x1)) → c2(x1) (41)
c1(b1(x1)) → c1(x1) (42)
c1(b0(x1)) → c0(x1) (43)
a0(c1(x1)) → a1(x1) (45)
(w.r.t. the implicit argument filter of the reduction pair), the pairs
c1#(b2(x1)) → c2#(x1) (54)
c2#(a1(b0(c0(x1)))) → c1#(b0(x1)) (55)
c2#(a1(b0(c0(x1)))) → c1#(b2(a2(a0(c1(b0(x1)))))) (56)
c2#(a1(b0(c0(x1)))) → b2#(a2(a0(c1(b0(x1))))) (57)
c2#(a1(b0(c0(x1)))) → a0#(c1(b0(x1))) (58)
c2#(a1(b0(c0(x1)))) → a2#(a0(c1(b0(x1)))) (59)
c2#(a1(b0(c1(x1)))) → c1#(b1(x1)) (60)
c2#(a1(b0(c1(x1)))) → c1#(b2(a2(a0(c1(b1(x1)))))) (61)
c2#(a1(b0(c1(x1)))) → b1#(x1) (62)
c2#(a1(b0(c1(x1)))) → b2#(a2(a0(c1(b1(x1))))) (63)
c2#(a1(b0(c1(x1)))) → a0#(c1(b1(x1))) (64)
c2#(a1(b0(c1(x1)))) → a2#(a0(c1(b1(x1)))) (65)
c2#(a1(b0(c2(x1)))) → c1#(b2(x1)) (66)
c2#(a1(b0(c2(x1)))) → c1#(b2(a2(a0(c1(b2(x1)))))) (67)
c2#(a1(b0(c2(x1)))) → b2#(x1) (68)
c2#(a1(b0(c2(x1)))) → b2#(a2(a0(c1(b2(x1))))) (69)
c2#(a1(b0(c2(x1)))) → a0#(c1(b2(x1))) (70)
c2#(a1(b0(c2(x1)))) → a2#(a0(c1(b2(x1)))) (71)
b2#(a1(b0(c0(x1)))) → c1#(b0(x1)) (73)
b2#(a1(b0(c0(x1)))) → c1#(b2(a2(a0(c1(b0(x1)))))) (74)
b2#(a1(b0(c0(x1)))) → b2#(a2(a0(c1(b0(x1))))) (75)
b2#(a1(b0(c0(x1)))) → a0#(c1(b0(x1))) (76)
b2#(a1(b0(c0(x1)))) → a2#(a0(c1(b0(x1)))) (77)
b2#(a1(b0(c1(x1)))) → c1#(b1(x1)) (78)
b2#(a1(b0(c1(x1)))) → c1#(b2(a2(a0(c1(b1(x1)))))) (79)
b2#(a1(b0(c1(x1)))) → b1#(x1) (80)
b2#(a1(b0(c1(x1)))) → b2#(a2(a0(c1(b1(x1))))) (81)
b2#(a1(b0(c1(x1)))) → a0#(c1(b1(x1))) (82)
b2#(a1(b0(c1(x1)))) → a2#(a0(c1(b1(x1)))) (83)
b2#(a1(b0(c2(x1)))) → c1#(b2(x1)) (84)
b2#(a1(b0(c2(x1)))) → c1#(b2(a2(a0(c1(b2(x1)))))) (85)
b2#(a1(b0(c2(x1)))) → b2#(x1) (86)
b2#(a1(b0(c2(x1)))) → b2#(a2(a0(c1(b2(x1))))) (87)
b2#(a1(b0(c2(x1)))) → a0#(c1(b2(x1))) (88)
b2#(a1(b0(c2(x1)))) → a2#(a0(c1(b2(x1)))) (89)
a0#(c1(x1)) → a1#(x1) (91)
a2#(a1(b0(c0(x1)))) → c1#(b0(x1)) (93)
a2#(a1(b0(c0(x1)))) → c1#(b2(a2(a0(c1(b0(x1)))))) (94)
a2#(a1(b0(c0(x1)))) → b2#(a2(a0(c1(b0(x1))))) (95)
a2#(a1(b0(c0(x1)))) → a0#(c1(b0(x1))) (96)
a2#(a1(b0(c0(x1)))) → a0#(c1(b2(a2(a0(c1(b0(x1))))))) (97)
a2#(a1(b0(c0(x1)))) → a2#(a0(c1(b0(x1)))) (98)
a2#(a1(b0(c1(x1)))) → c1#(b1(x1)) (99)
a2#(a1(b0(c1(x1)))) → c1#(b2(a2(a0(c1(b1(x1)))))) (100)
a2#(a1(b0(c1(x1)))) → b1#(x1) (101)
a2#(a1(b0(c1(x1)))) → b2#(a2(a0(c1(b1(x1))))) (102)
a2#(a1(b0(c1(x1)))) → a0#(c1(b1(x1))) (103)
a2#(a1(b0(c1(x1)))) → a0#(c1(b2(a2(a0(c1(b1(x1))))))) (104)
a2#(a1(b0(c1(x1)))) → a2#(a0(c1(b1(x1)))) (105)
a2#(a1(b0(c2(x1)))) → c1#(b2(x1)) (106)
a2#(a1(b0(c2(x1)))) → c1#(b2(a2(a0(c1(b2(x1)))))) (107)
a2#(a1(b0(c2(x1)))) → b2#(x1) (108)
a2#(a1(b0(c2(x1)))) → b2#(a2(a0(c1(b2(x1))))) (109)
a2#(a1(b0(c2(x1)))) → a0#(c1(b2(x1))) (110)
a2#(a1(b0(c2(x1)))) → a0#(c1(b2(a2(a0(c1(b2(x1))))))) (111)
a2#(a1(b0(c2(x1)))) → a2#(a0(c1(b2(x1)))) (112)
and no rules could be deleted.

1.1.1.1.1.1 Dependency Graph Processor

The dependency pairs are split into 4 components.