Certification Problem

Input (TPDB SRS_Relative/Waldmann_19/random-81)

The relative rewrite relation R/S is considered where R is the following TRS

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

and S is the following TRS.

c(b(b(x1))) → b(a(a(x1))) (4)
c(b(a(x1))) → b(c(c(x1))) (5)
b(a(a(x1))) → c(a(a(x1))) (6)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 Closure Under Flat Contexts

Using the flat contexts

{a(☐), b(☐), c(☐)}

We obtain the transformed TRS
a(a(b(x1))) → a(c(b(x1))) (3)
a(a(b(b(x1)))) → a(c(b(a(x1)))) (7)
b(a(b(b(x1)))) → b(c(b(a(x1)))) (8)
c(a(b(b(x1)))) → c(c(b(a(x1)))) (9)
a(a(a(c(x1)))) → a(b(c(a(x1)))) (10)
b(a(a(c(x1)))) → b(b(c(a(x1)))) (11)
c(a(a(c(x1)))) → c(b(c(a(x1)))) (12)
a(c(b(b(x1)))) → a(b(a(a(x1)))) (13)
b(c(b(b(x1)))) → b(b(a(a(x1)))) (14)
c(c(b(b(x1)))) → c(b(a(a(x1)))) (15)
a(c(b(a(x1)))) → a(b(c(c(x1)))) (16)
b(c(b(a(x1)))) → b(b(c(c(x1)))) (17)
c(c(b(a(x1)))) → c(b(c(c(x1)))) (18)
a(b(a(a(x1)))) → a(c(a(a(x1)))) (19)
b(b(a(a(x1)))) → b(c(a(a(x1)))) (20)
c(b(a(a(x1)))) → c(c(a(a(x1)))) (21)

1.1 Semantic Labeling

Root-labeling is applied.

We obtain the labeled TRS
aa(ab(ba(x1))) → ac(cb(ba(x1))) (22)
aa(ab(bb(x1))) → ac(cb(bb(x1))) (23)
aa(ab(bc(x1))) → ac(cb(bc(x1))) (24)
aa(ab(bb(ba(x1)))) → ac(cb(ba(aa(x1)))) (25)
aa(ab(bb(bb(x1)))) → ac(cb(ba(ab(x1)))) (26)
aa(ab(bb(bc(x1)))) → ac(cb(ba(ac(x1)))) (27)
ba(ab(bb(ba(x1)))) → bc(cb(ba(aa(x1)))) (28)
ba(ab(bb(bb(x1)))) → bc(cb(ba(ab(x1)))) (29)
ba(ab(bb(bc(x1)))) → bc(cb(ba(ac(x1)))) (30)
ca(ab(bb(ba(x1)))) → cc(cb(ba(aa(x1)))) (31)
ca(ab(bb(bb(x1)))) → cc(cb(ba(ab(x1)))) (32)
ca(ab(bb(bc(x1)))) → cc(cb(ba(ac(x1)))) (33)
aa(aa(ac(ca(x1)))) → ab(bc(ca(aa(x1)))) (34)
aa(aa(ac(cb(x1)))) → ab(bc(ca(ab(x1)))) (35)
aa(aa(ac(cc(x1)))) → ab(bc(ca(ac(x1)))) (36)
ba(aa(ac(ca(x1)))) → bb(bc(ca(aa(x1)))) (37)
ba(aa(ac(cb(x1)))) → bb(bc(ca(ab(x1)))) (38)
ba(aa(ac(cc(x1)))) → bb(bc(ca(ac(x1)))) (39)
ca(aa(ac(ca(x1)))) → cb(bc(ca(aa(x1)))) (40)
ca(aa(ac(cb(x1)))) → cb(bc(ca(ab(x1)))) (41)
ca(aa(ac(cc(x1)))) → cb(bc(ca(ac(x1)))) (42)
ac(cb(bb(ba(x1)))) → ab(ba(aa(aa(x1)))) (43)
ac(cb(bb(bb(x1)))) → ab(ba(aa(ab(x1)))) (44)
ac(cb(bb(bc(x1)))) → ab(ba(aa(ac(x1)))) (45)
bc(cb(bb(ba(x1)))) → bb(ba(aa(aa(x1)))) (46)
bc(cb(bb(bb(x1)))) → bb(ba(aa(ab(x1)))) (47)
bc(cb(bb(bc(x1)))) → bb(ba(aa(ac(x1)))) (48)
cc(cb(bb(ba(x1)))) → cb(ba(aa(aa(x1)))) (49)
cc(cb(bb(bb(x1)))) → cb(ba(aa(ab(x1)))) (50)
cc(cb(bb(bc(x1)))) → cb(ba(aa(ac(x1)))) (51)
ac(cb(ba(aa(x1)))) → ab(bc(cc(ca(x1)))) (52)
ac(cb(ba(ab(x1)))) → ab(bc(cc(cb(x1)))) (53)
ac(cb(ba(ac(x1)))) → ab(bc(cc(cc(x1)))) (54)
bc(cb(ba(aa(x1)))) → bb(bc(cc(ca(x1)))) (55)
bc(cb(ba(ab(x1)))) → bb(bc(cc(cb(x1)))) (56)
bc(cb(ba(ac(x1)))) → bb(bc(cc(cc(x1)))) (57)
cc(cb(ba(aa(x1)))) → cb(bc(cc(ca(x1)))) (58)
cc(cb(ba(ab(x1)))) → cb(bc(cc(cb(x1)))) (59)
cc(cb(ba(ac(x1)))) → cb(bc(cc(cc(x1)))) (60)
ab(ba(aa(aa(x1)))) → ac(ca(aa(aa(x1)))) (61)
ab(ba(aa(ab(x1)))) → ac(ca(aa(ab(x1)))) (62)
ab(ba(aa(ac(x1)))) → ac(ca(aa(ac(x1)))) (63)
bb(ba(aa(aa(x1)))) → bc(ca(aa(aa(x1)))) (64)
bb(ba(aa(ab(x1)))) → bc(ca(aa(ab(x1)))) (65)
bb(ba(aa(ac(x1)))) → bc(ca(aa(ac(x1)))) (66)
cb(ba(aa(aa(x1)))) → cc(ca(aa(aa(x1)))) (67)
cb(ba(aa(ab(x1)))) → cc(ca(aa(ab(x1)))) (68)
cb(ba(aa(ac(x1)))) → cc(ca(aa(ac(x1)))) (69)

1.1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[aa(x1)] = 2 · x1
[ab(x1)] = 2 · x1
[ba(x1)] = 3 + 2 · x1
[ac(x1)] = 1 · x1
[cb(x1)] = 4 · x1
[bb(x1)] = 3 + 2 · x1
[bc(x1)] = 1 · x1
[ca(x1)] = 4 · x1
[cc(x1)] = 2 · x1
all of the following rules can be deleted.
aa(ab(bb(ba(x1)))) → ac(cb(ba(aa(x1)))) (25)
aa(ab(bb(bb(x1)))) → ac(cb(ba(ab(x1)))) (26)
ba(ab(bb(ba(x1)))) → bc(cb(ba(aa(x1)))) (28)
ba(ab(bb(bb(x1)))) → bc(cb(ba(ab(x1)))) (29)
ba(ab(bb(bc(x1)))) → bc(cb(ba(ac(x1)))) (30)
ca(ab(bb(ba(x1)))) → cc(cb(ba(aa(x1)))) (31)
ca(ab(bb(bb(x1)))) → cc(cb(ba(ab(x1)))) (32)
ac(cb(bb(ba(x1)))) → ab(ba(aa(aa(x1)))) (43)
ac(cb(bb(bb(x1)))) → ab(ba(aa(ab(x1)))) (44)
ac(cb(bb(bc(x1)))) → ab(ba(aa(ac(x1)))) (45)
bc(cb(bb(ba(x1)))) → bb(ba(aa(aa(x1)))) (46)
bc(cb(bb(bb(x1)))) → bb(ba(aa(ab(x1)))) (47)
bc(cb(bb(bc(x1)))) → bb(ba(aa(ac(x1)))) (48)
cc(cb(bb(ba(x1)))) → cb(ba(aa(aa(x1)))) (49)
cc(cb(bb(bb(x1)))) → cb(ba(aa(ab(x1)))) (50)
cc(cb(bb(bc(x1)))) → cb(ba(aa(ac(x1)))) (51)
ac(cb(ba(aa(x1)))) → ab(bc(cc(ca(x1)))) (52)
ac(cb(ba(ab(x1)))) → ab(bc(cc(cb(x1)))) (53)
ac(cb(ba(ac(x1)))) → ab(bc(cc(cc(x1)))) (54)
bc(cb(ba(aa(x1)))) → bb(bc(cc(ca(x1)))) (55)
bc(cb(ba(ab(x1)))) → bb(bc(cc(cb(x1)))) (56)
bc(cb(ba(ac(x1)))) → bb(bc(cc(cc(x1)))) (57)
cc(cb(ba(aa(x1)))) → cb(bc(cc(ca(x1)))) (58)
cc(cb(ba(ab(x1)))) → cb(bc(cc(cb(x1)))) (59)
cc(cb(ba(ac(x1)))) → cb(bc(cc(cc(x1)))) (60)
ab(ba(aa(aa(x1)))) → ac(ca(aa(aa(x1)))) (61)
ab(ba(aa(ab(x1)))) → ac(ca(aa(ab(x1)))) (62)
ab(ba(aa(ac(x1)))) → ac(ca(aa(ac(x1)))) (63)
bb(ba(aa(aa(x1)))) → bc(ca(aa(aa(x1)))) (64)
bb(ba(aa(ab(x1)))) → bc(ca(aa(ab(x1)))) (65)
bb(ba(aa(ac(x1)))) → bc(ca(aa(ac(x1)))) (66)
cb(ba(aa(aa(x1)))) → cc(ca(aa(aa(x1)))) (67)
cb(ba(aa(ab(x1)))) → cc(ca(aa(ab(x1)))) (68)
cb(ba(aa(ac(x1)))) → cc(ca(aa(ac(x1)))) (69)

1.1.1.1 String Reversal

Since only unary symbols occur, one can reverse all terms and obtains the TRS
ba(ab(aa(x1))) → ba(cb(ac(x1))) (70)
bb(ab(aa(x1))) → bb(cb(ac(x1))) (71)
bc(ab(aa(x1))) → bc(cb(ac(x1))) (72)
bc(bb(ab(aa(x1)))) → ac(ba(cb(ac(x1)))) (73)
bc(bb(ab(ca(x1)))) → ac(ba(cb(cc(x1)))) (74)
ca(ac(aa(aa(x1)))) → aa(ca(bc(ab(x1)))) (75)
cb(ac(aa(aa(x1)))) → ab(ca(bc(ab(x1)))) (76)
cc(ac(aa(aa(x1)))) → ac(ca(bc(ab(x1)))) (77)
ca(ac(aa(ba(x1)))) → aa(ca(bc(bb(x1)))) (78)
cb(ac(aa(ba(x1)))) → ab(ca(bc(bb(x1)))) (79)
cc(ac(aa(ba(x1)))) → ac(ca(bc(bb(x1)))) (80)
ca(ac(aa(ca(x1)))) → aa(ca(bc(cb(x1)))) (81)
cb(ac(aa(ca(x1)))) → ab(ca(bc(cb(x1)))) (82)
cc(ac(aa(ca(x1)))) → ac(ca(bc(cb(x1)))) (83)

1.1.1.1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[ba(x1)] = 1 · x1 + 1
[ab(x1)] = 1 · x1 + 2
[aa(x1)] = 1 · x1 + 2
[cb(x1)] = 1 · x1 + 1
[ac(x1)] = 1 · x1
[bb(x1)] = 1 · x1
[bc(x1)] = 1 · x1
[ca(x1)] = 1 · x1 + 1
[cc(x1)] = 1 · x1
all of the following rules can be deleted.
ba(ab(aa(x1))) → ba(cb(ac(x1))) (70)
bb(ab(aa(x1))) → bb(cb(ac(x1))) (71)
bc(ab(aa(x1))) → bc(cb(ac(x1))) (72)
bc(bb(ab(aa(x1)))) → ac(ba(cb(ac(x1)))) (73)
bc(bb(ab(ca(x1)))) → ac(ba(cb(cc(x1)))) (74)
cc(ac(aa(aa(x1)))) → ac(ca(bc(ab(x1)))) (77)
ca(ac(aa(ba(x1)))) → aa(ca(bc(bb(x1)))) (78)
cb(ac(aa(ba(x1)))) → ab(ca(bc(bb(x1)))) (79)
cc(ac(aa(ba(x1)))) → ac(ca(bc(bb(x1)))) (80)
cc(ac(aa(ca(x1)))) → ac(ca(bc(cb(x1)))) (83)

1.1.1.1.1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[ca(x1)] = 1 · x1 + 2
[ac(x1)] = 1 · x1
[aa(x1)] = 1 · x1 + 1
[bc(x1)] = 1 · x1
[ab(x1)] = 1 · x1
[cb(x1)] = 1 · x1
all of the following rules can be deleted.
ca(ac(aa(aa(x1)))) → aa(ca(bc(ab(x1)))) (75)
ca(ac(aa(ca(x1)))) → aa(ca(bc(cb(x1)))) (81)
cb(ac(aa(ca(x1)))) → ab(ca(bc(cb(x1)))) (82)

1.1.1.1.1.1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[cb(x1)] = 1 · x1
[ac(x1)] = 1 · x1 + 1
[aa(x1)] = 1 · x1
[ab(x1)] = 1 · x1
[ca(x1)] = 1 · x1
[bc(x1)] = 1 · x1
all of the following rules can be deleted.
cb(ac(aa(aa(x1)))) → ab(ca(bc(ab(x1)))) (76)

1.1.1.1.1.1.1.1 R is empty

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