Certification Problem

Input (TPDB SRS_Relative/Waldmann_19/random-210)

The rewrite relation of the following TRS is considered.

b(b(c(x1))) → b(a(a(x1))) (1)
a(c(c(x1))) → a(a(b(x1))) (2)
a(c(b(x1))) → c(a(b(x1))) (3)
a(c(c(x1))) → c(c(b(x1))) (4)
a(a(a(x1))) → a(b(a(x1))) (5)
a(b(a(x1))) → a(b(c(x1))) (6)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by matchbox @ termCOMP 2023)

1 Split

We split R in the relative problem D/R-D and R-D, where the rules D

a(c(c(x1))) → a(a(b(x1))) (2)
a(a(a(x1))) → a(b(a(x1))) (5)
are deleted.

1.1 Closure Under Flat Contexts

Using the flat contexts

{c(☐), b(☐), a(☐)}

We obtain the transformed TRS
c(a(c(c(x1)))) → c(a(a(b(x1)))) (7)
c(a(a(a(x1)))) → c(a(b(a(x1)))) (8)
b(a(c(c(x1)))) → b(a(a(b(x1)))) (9)
b(a(a(a(x1)))) → b(a(b(a(x1)))) (10)
a(a(c(c(x1)))) → a(a(a(b(x1)))) (11)
a(a(a(a(x1)))) → a(a(b(a(x1)))) (12)
c(b(b(c(x1)))) → c(b(a(a(x1)))) (13)
c(a(c(b(x1)))) → c(c(a(b(x1)))) (14)
c(a(c(c(x1)))) → c(c(c(b(x1)))) (15)
c(a(b(a(x1)))) → c(a(b(c(x1)))) (16)
b(b(b(c(x1)))) → b(b(a(a(x1)))) (17)
b(a(c(b(x1)))) → b(c(a(b(x1)))) (18)
b(a(c(c(x1)))) → b(c(c(b(x1)))) (19)
b(a(b(a(x1)))) → b(a(b(c(x1)))) (20)
a(b(b(c(x1)))) → a(b(a(a(x1)))) (21)
a(a(c(b(x1)))) → a(c(a(b(x1)))) (22)
a(a(c(c(x1)))) → a(c(c(b(x1)))) (23)
a(a(b(a(x1)))) → a(a(b(c(x1)))) (24)

1.1.1 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
b2(a0(c0(c1(x1)))) → b2(a2(a1(b1(x1)))) (25)
b2(a0(c0(c0(x1)))) → b2(a2(a1(b0(x1)))) (26)
b2(a0(c0(c2(x1)))) → b2(a2(a1(b2(x1)))) (27)
c2(a0(c0(c1(x1)))) → c2(a2(a1(b1(x1)))) (28)
c2(a0(c0(c0(x1)))) → c2(a2(a1(b0(x1)))) (29)
c2(a0(c0(c2(x1)))) → c2(a2(a1(b2(x1)))) (30)
a2(a0(c0(c1(x1)))) → a2(a2(a1(b1(x1)))) (31)
a2(a0(c0(c0(x1)))) → a2(a2(a1(b0(x1)))) (32)
a2(a0(c0(c2(x1)))) → a2(a2(a1(b2(x1)))) (33)
b2(a2(a2(a1(x1)))) → b2(a1(b2(a1(x1)))) (34)
b2(a2(a2(a0(x1)))) → b2(a1(b2(a0(x1)))) (35)
b2(a2(a2(a2(x1)))) → b2(a1(b2(a2(x1)))) (36)
c2(a2(a2(a1(x1)))) → c2(a1(b2(a1(x1)))) (37)
c2(a2(a2(a0(x1)))) → c2(a1(b2(a0(x1)))) (38)
c2(a2(a2(a2(x1)))) → c2(a1(b2(a2(x1)))) (39)
a2(a2(a2(a1(x1)))) → a2(a1(b2(a1(x1)))) (40)
a2(a2(a2(a0(x1)))) → a2(a1(b2(a0(x1)))) (41)
a2(a2(a2(a2(x1)))) → a2(a1(b2(a2(x1)))) (42)
b1(b1(b0(c1(x1)))) → b1(b2(a2(a1(x1)))) (43)
b1(b1(b0(c0(x1)))) → b1(b2(a2(a0(x1)))) (44)
b1(b1(b0(c2(x1)))) → b1(b2(a2(a2(x1)))) (45)
c1(b1(b0(c1(x1)))) → c1(b2(a2(a1(x1)))) (46)
c1(b1(b0(c0(x1)))) → c1(b2(a2(a0(x1)))) (47)
c1(b1(b0(c2(x1)))) → c1(b2(a2(a2(x1)))) (48)
a1(b1(b0(c1(x1)))) → a1(b2(a2(a1(x1)))) (49)
a1(b1(b0(c0(x1)))) → a1(b2(a2(a0(x1)))) (50)
a1(b1(b0(c2(x1)))) → a1(b2(a2(a2(x1)))) (51)
b2(a0(c1(b1(x1)))) → b0(c2(a1(b1(x1)))) (52)
b2(a0(c1(b0(x1)))) → b0(c2(a1(b0(x1)))) (53)
b2(a0(c1(b2(x1)))) → b0(c2(a1(b2(x1)))) (54)
c2(a0(c1(b1(x1)))) → c0(c2(a1(b1(x1)))) (55)
c2(a0(c1(b0(x1)))) → c0(c2(a1(b0(x1)))) (56)
c2(a0(c1(b2(x1)))) → c0(c2(a1(b2(x1)))) (57)
a2(a0(c1(b1(x1)))) → a0(c2(a1(b1(x1)))) (58)
a2(a0(c1(b0(x1)))) → a0(c2(a1(b0(x1)))) (59)
a2(a0(c1(b2(x1)))) → a0(c2(a1(b2(x1)))) (60)
b2(a0(c0(c1(x1)))) → b0(c0(c1(b1(x1)))) (61)
b2(a0(c0(c0(x1)))) → b0(c0(c1(b0(x1)))) (62)
b2(a0(c0(c2(x1)))) → b0(c0(c1(b2(x1)))) (63)
c2(a0(c0(c1(x1)))) → c0(c0(c1(b1(x1)))) (64)
c2(a0(c0(c0(x1)))) → c0(c0(c1(b0(x1)))) (65)
c2(a0(c0(c2(x1)))) → c0(c0(c1(b2(x1)))) (66)
a2(a0(c0(c1(x1)))) → a0(c0(c1(b1(x1)))) (67)
a2(a0(c0(c0(x1)))) → a0(c0(c1(b0(x1)))) (68)
a2(a0(c0(c2(x1)))) → a0(c0(c1(b2(x1)))) (69)
b2(a1(b2(a1(x1)))) → b2(a1(b0(c1(x1)))) (70)
b2(a1(b2(a0(x1)))) → b2(a1(b0(c0(x1)))) (71)
b2(a1(b2(a2(x1)))) → b2(a1(b0(c2(x1)))) (72)
c2(a1(b2(a1(x1)))) → c2(a1(b0(c1(x1)))) (73)
c2(a1(b2(a0(x1)))) → c2(a1(b0(c0(x1)))) (74)
c2(a1(b2(a2(x1)))) → c2(a1(b0(c2(x1)))) (75)
a2(a1(b2(a1(x1)))) → a2(a1(b0(c1(x1)))) (76)
a2(a1(b2(a0(x1)))) → a2(a1(b0(c0(x1)))) (77)
a2(a1(b2(a2(x1)))) → a2(a1(b0(c2(x1)))) (78)

1.1.1.1 Rule Removal

Using the matrix interpretations of dimension 1 with strict dimension 1 over the rationals with delta = 1
[c0(x1)] = x1 +
3/2
[c1(x1)] = x1 +
0
[c2(x1)] = x1 +
1/2
[b0(x1)] = x1 +
0
[b1(x1)] = x1 +
1/2
[b2(x1)] = x1 +
0
[a0(x1)] = x1 +
3/2
[a1(x1)] = x1 +
0
[a2(x1)] = x1 +
1/2
all of the following rules can be deleted.
b2(a0(c0(c1(x1)))) → b2(a2(a1(b1(x1)))) (25)
b2(a0(c0(c0(x1)))) → b2(a2(a1(b0(x1)))) (26)
b2(a0(c0(c2(x1)))) → b2(a2(a1(b2(x1)))) (27)
c2(a0(c0(c1(x1)))) → c2(a2(a1(b1(x1)))) (28)
c2(a0(c0(c0(x1)))) → c2(a2(a1(b0(x1)))) (29)
c2(a0(c0(c2(x1)))) → c2(a2(a1(b2(x1)))) (30)
a2(a0(c0(c1(x1)))) → a2(a2(a1(b1(x1)))) (31)
a2(a0(c0(c0(x1)))) → a2(a2(a1(b0(x1)))) (32)
a2(a0(c0(c2(x1)))) → a2(a2(a1(b2(x1)))) (33)
b2(a2(a2(a1(x1)))) → b2(a1(b2(a1(x1)))) (34)
b2(a2(a2(a0(x1)))) → b2(a1(b2(a0(x1)))) (35)
b2(a2(a2(a2(x1)))) → b2(a1(b2(a2(x1)))) (36)
c2(a2(a2(a1(x1)))) → c2(a1(b2(a1(x1)))) (37)
c2(a2(a2(a0(x1)))) → c2(a1(b2(a0(x1)))) (38)
c2(a2(a2(a2(x1)))) → c2(a1(b2(a2(x1)))) (39)
a2(a2(a2(a1(x1)))) → a2(a1(b2(a1(x1)))) (40)
a2(a2(a2(a0(x1)))) → a2(a1(b2(a0(x1)))) (41)
a2(a2(a2(a2(x1)))) → a2(a1(b2(a2(x1)))) (42)
b2(a0(c1(b1(x1)))) → b0(c2(a1(b1(x1)))) (52)
b2(a0(c1(b0(x1)))) → b0(c2(a1(b0(x1)))) (53)
b2(a0(c1(b2(x1)))) → b0(c2(a1(b2(x1)))) (54)
b2(a0(c0(c1(x1)))) → b0(c0(c1(b1(x1)))) (61)
b2(a0(c0(c0(x1)))) → b0(c0(c1(b0(x1)))) (62)
b2(a0(c0(c2(x1)))) → b0(c0(c1(b2(x1)))) (63)
c2(a0(c0(c0(x1)))) → c0(c0(c1(b0(x1)))) (65)
c2(a0(c0(c2(x1)))) → c0(c0(c1(b2(x1)))) (66)
a2(a0(c0(c0(x1)))) → a0(c0(c1(b0(x1)))) (68)
a2(a0(c0(c2(x1)))) → a0(c0(c1(b2(x1)))) (69)

1.1.1.1.1 R is empty

There are no rules in the TRS. Hence, it is terminating.

1.2 Closure Under Flat Contexts

Using the flat contexts

{c(☐), b(☐), a(☐)}

We obtain the transformed TRS
c(b(b(c(x1)))) → c(b(a(a(x1)))) (13)
c(a(c(b(x1)))) → c(c(a(b(x1)))) (14)
c(a(c(c(x1)))) → c(c(c(b(x1)))) (15)
c(a(b(a(x1)))) → c(a(b(c(x1)))) (16)
b(b(b(c(x1)))) → b(b(a(a(x1)))) (17)
b(a(c(b(x1)))) → b(c(a(b(x1)))) (18)
b(a(c(c(x1)))) → b(c(c(b(x1)))) (19)
b(a(b(a(x1)))) → b(a(b(c(x1)))) (20)
a(b(b(c(x1)))) → a(b(a(a(x1)))) (21)
a(a(c(b(x1)))) → a(c(a(b(x1)))) (22)
a(a(c(c(x1)))) → a(c(c(b(x1)))) (23)
a(a(b(a(x1)))) → a(a(b(c(x1)))) (24)

1.2.1 Closure Under Flat Contexts

Using the flat contexts

{c(☐), b(☐), a(☐)}

We obtain the transformed TRS
c(c(b(b(c(x1))))) → c(c(b(a(a(x1))))) (79)
c(c(a(c(b(x1))))) → c(c(c(a(b(x1))))) (80)
c(c(a(c(c(x1))))) → c(c(c(c(b(x1))))) (81)
c(c(a(b(a(x1))))) → c(c(a(b(c(x1))))) (82)
c(b(b(b(c(x1))))) → c(b(b(a(a(x1))))) (83)
c(b(a(c(b(x1))))) → c(b(c(a(b(x1))))) (84)
c(b(a(c(c(x1))))) → c(b(c(c(b(x1))))) (85)
c(b(a(b(a(x1))))) → c(b(a(b(c(x1))))) (86)
c(a(b(b(c(x1))))) → c(a(b(a(a(x1))))) (87)
c(a(a(c(b(x1))))) → c(a(c(a(b(x1))))) (88)
c(a(a(c(c(x1))))) → c(a(c(c(b(x1))))) (89)
c(a(a(b(a(x1))))) → c(a(a(b(c(x1))))) (90)
b(c(b(b(c(x1))))) → b(c(b(a(a(x1))))) (91)
b(c(a(c(b(x1))))) → b(c(c(a(b(x1))))) (92)
b(c(a(c(c(x1))))) → b(c(c(c(b(x1))))) (93)
b(c(a(b(a(x1))))) → b(c(a(b(c(x1))))) (94)
b(b(b(b(c(x1))))) → b(b(b(a(a(x1))))) (95)
b(b(a(c(b(x1))))) → b(b(c(a(b(x1))))) (96)
b(b(a(c(c(x1))))) → b(b(c(c(b(x1))))) (97)
b(b(a(b(a(x1))))) → b(b(a(b(c(x1))))) (98)
b(a(b(b(c(x1))))) → b(a(b(a(a(x1))))) (99)
b(a(a(c(b(x1))))) → b(a(c(a(b(x1))))) (100)
b(a(a(c(c(x1))))) → b(a(c(c(b(x1))))) (101)
b(a(a(b(a(x1))))) → b(a(a(b(c(x1))))) (102)
a(c(b(b(c(x1))))) → a(c(b(a(a(x1))))) (103)
a(c(a(c(b(x1))))) → a(c(c(a(b(x1))))) (104)
a(c(a(c(c(x1))))) → a(c(c(c(b(x1))))) (105)
a(c(a(b(a(x1))))) → a(c(a(b(c(x1))))) (106)
a(b(b(b(c(x1))))) → a(b(b(a(a(x1))))) (107)
a(b(a(c(b(x1))))) → a(b(c(a(b(x1))))) (108)
a(b(a(c(c(x1))))) → a(b(c(c(b(x1))))) (109)
a(b(a(b(a(x1))))) → a(b(a(b(c(x1))))) (110)
a(a(b(b(c(x1))))) → a(a(b(a(a(x1))))) (111)
a(a(a(c(b(x1))))) → a(a(c(a(b(x1))))) (112)
a(a(a(c(c(x1))))) → a(a(c(c(b(x1))))) (113)
a(a(a(b(a(x1))))) → a(a(a(b(c(x1))))) (114)

1.2.1.1 Semantic Labeling

The following interpretations form a model of the rules.

As carrier we take the set {0,...,8}. Symbols are labeled by the interpretation of their arguments using the interpretations (modulo 9):

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

We obtain the labeled TRS

There are 324 ruless (increase limit for explicit display).

1.2.1.1.1 Rule Removal

Using the matrix interpretations of dimension 1 with strict dimension 1 over the rationals with delta = 1
[c0(x1)] = x1 +
26
[c3(x1)] = x1 +
5
[c6(x1)] = x1 +
42
[c1(x1)] = x1 +
42
[c4(x1)] = x1 +
21
[c7(x1)] = x1 +
1
[c2(x1)] = x1 +
42
[c5(x1)] = x1 +
0
[c8(x1)] = x1 +
42
[b0(x1)] = x1 +
0
[b3(x1)] = x1 +
0
[b6(x1)] = x1 +
0
[b1(x1)] = x1 +
42
[b4(x1)] = x1 +
21
[b7(x1)] = x1 +
0
[b2(x1)] = x1 +
21
[b5(x1)] = x1 +
47
[b8(x1)] = x1 +
1
[a0(x1)] = x1 +
43
[a3(x1)] = x1 +
22
[a6(x1)] = x1 +
42
[a1(x1)] = x1 +
0
[a4(x1)] = x1 +
21
[a7(x1)] = x1 +
0
[a2(x1)] = x1 +
43
[a5(x1)] = x1 +
5
[a8(x1)] = x1 +
47
all of the following rules can be deleted.

There are 324 ruless (increase limit for explicit display).

1.2.1.1.1.1 R is empty

There are no rules in the TRS. Hence, it is terminating.