Certification Problem

Input (TPDB SRS_Relative/Waldmann_19/random-172)

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

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

and S is the following TRS.

c(a(a(x1))) → a(a(a(x1))) (3)
b(b(b(x1))) → c(c(b(x1))) (4)
a(c(a(x1))) → a(b(b(x1))) (5)
b(a(c(x1))) → a(a(c(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(☐), c(☐), b(☐)}

We obtain the transformed TRS
a(a(a(c(x1)))) → a(b(b(c(x1)))) (7)
c(a(a(c(x1)))) → c(b(b(c(x1)))) (8)
b(a(a(c(x1)))) → b(b(b(c(x1)))) (9)
a(b(a(c(x1)))) → a(a(a(b(x1)))) (10)
c(b(a(c(x1)))) → c(a(a(b(x1)))) (11)
b(b(a(c(x1)))) → b(a(a(b(x1)))) (12)
a(c(a(x1))) → a(b(b(x1))) (5)
a(c(a(a(x1)))) → a(a(a(a(x1)))) (13)
c(c(a(a(x1)))) → c(a(a(a(x1)))) (14)
b(c(a(a(x1)))) → b(a(a(a(x1)))) (15)
a(b(b(b(x1)))) → a(c(c(b(x1)))) (16)
c(b(b(b(x1)))) → c(c(c(b(x1)))) (17)
b(b(b(b(x1)))) → b(c(c(b(x1)))) (18)
a(b(a(c(x1)))) → a(a(a(c(x1)))) (19)
c(b(a(c(x1)))) → c(a(a(c(x1)))) (20)
b(b(a(c(x1)))) → b(a(a(c(x1)))) (21)

1.1 Semantic Labeling

Root-labeling is applied.

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

1.1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[aa(x1)] = 1 · x1
[ac(x1)] = 1 + 1 · x1
[ca(x1)] = 1 + 1 · x1
[ab(x1)] = 1 · x1
[bb(x1)] = 1 + 1 · x1
[bc(x1)] = 1 · x1
[cc(x1)] = 1 + 1 · x1
[cb(x1)] = 1 · x1
[ba(x1)] = 1 + 1 · x1
all of the following rules can be deleted.
ca(aa(ac(ca(x1)))) → cb(bb(bc(ca(x1)))) (25)
ca(aa(ac(cc(x1)))) → cb(bb(bc(cc(x1)))) (26)
ca(aa(ac(cb(x1)))) → cb(bb(bc(cb(x1)))) (27)
ab(ba(ac(ca(x1)))) → aa(aa(ab(ba(x1)))) (31)
ab(ba(ac(cc(x1)))) → aa(aa(ab(bc(x1)))) (32)
ab(ba(ac(cb(x1)))) → aa(aa(ab(bb(x1)))) (33)
cb(ba(ac(ca(x1)))) → ca(aa(ab(ba(x1)))) (34)
cb(ba(ac(cc(x1)))) → ca(aa(ab(bc(x1)))) (35)
bb(ba(ac(ca(x1)))) → ba(aa(ab(ba(x1)))) (37)
bb(ba(ac(cc(x1)))) → ba(aa(ab(bc(x1)))) (38)
bb(ba(ac(cb(x1)))) → ba(aa(ab(bb(x1)))) (39)
ac(ca(ac(x1))) → ab(bb(bc(x1))) (41)
ac(ca(aa(aa(x1)))) → aa(aa(aa(aa(x1)))) (43)
ac(ca(aa(ac(x1)))) → aa(aa(aa(ac(x1)))) (44)
ac(ca(aa(ab(x1)))) → aa(aa(aa(ab(x1)))) (45)
cc(ca(aa(aa(x1)))) → ca(aa(aa(aa(x1)))) (46)
cc(ca(aa(ac(x1)))) → ca(aa(aa(ac(x1)))) (47)
cc(ca(aa(ab(x1)))) → ca(aa(aa(ab(x1)))) (48)
bb(bb(bb(ba(x1)))) → bc(cc(cb(ba(x1)))) (58)
bb(bb(bb(bc(x1)))) → bc(cc(cb(bc(x1)))) (59)
bb(bb(bb(bb(x1)))) → bc(cc(cb(bb(x1)))) (60)
ab(ba(ac(ca(x1)))) → aa(aa(ac(ca(x1)))) (61)
ab(ba(ac(cc(x1)))) → aa(aa(ac(cc(x1)))) (62)
ab(ba(ac(cb(x1)))) → aa(aa(ac(cb(x1)))) (63)
bb(ba(ac(ca(x1)))) → ba(aa(ac(ca(x1)))) (67)
bb(ba(ac(cc(x1)))) → ba(aa(ac(cc(x1)))) (68)
bb(ba(ac(cb(x1)))) → ba(aa(ac(cb(x1)))) (69)

1.1.1.1 Rule Removal

Using the Knuth Bendix order with w0 = 1 and the following precedence and weight functions
prec(aa) = 8 weight(aa) = 10
prec(ac) = 5 weight(ac) = 6
prec(ca) = 6 weight(ca) = 9
prec(ab) = 7 weight(ab) = 6
prec(bb) = 4 weight(bb) = 7
prec(bc) = 3 weight(bc) = 10
prec(cc) = 2 weight(cc) = 2
prec(cb) = 0 weight(cb) = 11
prec(ba) = 1 weight(ba) = 9
all of the following rules can be deleted.
aa(aa(ac(ca(x1)))) → ab(bb(bc(ca(x1)))) (22)
aa(aa(ac(cc(x1)))) → ab(bb(bc(cc(x1)))) (23)
aa(aa(ac(cb(x1)))) → ab(bb(bc(cb(x1)))) (24)
ba(aa(ac(ca(x1)))) → bb(bb(bc(ca(x1)))) (28)
ba(aa(ac(cc(x1)))) → bb(bb(bc(cc(x1)))) (29)
ba(aa(ac(cb(x1)))) → bb(bb(bc(cb(x1)))) (30)
cb(ba(ac(cb(x1)))) → ca(aa(ab(bb(x1)))) (36)
ac(ca(aa(x1))) → ab(bb(ba(x1))) (40)
ac(ca(ab(x1))) → ab(bb(bb(x1))) (42)
bc(ca(aa(aa(x1)))) → ba(aa(aa(aa(x1)))) (49)
bc(ca(aa(ac(x1)))) → ba(aa(aa(ac(x1)))) (50)
bc(ca(aa(ab(x1)))) → ba(aa(aa(ab(x1)))) (51)
ab(bb(bb(ba(x1)))) → ac(cc(cb(ba(x1)))) (52)
ab(bb(bb(bc(x1)))) → ac(cc(cb(bc(x1)))) (53)
ab(bb(bb(bb(x1)))) → ac(cc(cb(bb(x1)))) (54)
cb(bb(bb(ba(x1)))) → cc(cc(cb(ba(x1)))) (55)
cb(bb(bb(bc(x1)))) → cc(cc(cb(bc(x1)))) (56)
cb(bb(bb(bb(x1)))) → cc(cc(cb(bb(x1)))) (57)
cb(ba(ac(ca(x1)))) → ca(aa(ac(ca(x1)))) (64)
cb(ba(ac(cc(x1)))) → ca(aa(ac(cc(x1)))) (65)
cb(ba(ac(cb(x1)))) → ca(aa(ac(cb(x1)))) (66)

1.1.1.1.1 R is empty

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