Certification Problem

Input (TPDB SRS_Standard/Waldmann_19/random-289)

The rewrite relation of the following TRS is considered.

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

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
a#(a(a(a(x1)))) a#(b(a(b(x1)))) (5)
a#(a(a(a(x1)))) b#(a(b(x1))) (6)
a#(a(a(a(x1)))) a#(b(x1)) (7)
a#(a(a(a(x1)))) b#(x1) (8)
b#(b(a(b(x1)))) b#(b(b(b(x1)))) (9)
b#(b(a(b(x1)))) b#(b(b(x1))) (10)
b#(b(a(b(x1)))) b#(b(x1)) (11)
a#(a(a(b(x1)))) b#(a(b(b(x1)))) (12)
a#(a(a(b(x1)))) a#(b(b(x1))) (13)
a#(a(a(b(x1)))) b#(b(x1)) (14)
b#(a(b(b(x1)))) b#(a(b(a(x1)))) (15)
b#(a(b(b(x1)))) a#(b(a(x1))) (16)
b#(a(b(b(x1)))) b#(a(x1)) (17)
b#(a(b(b(x1)))) a#(x1) (18)

1.1 Reduction Pair Processor

Using the linear polynomial interpretation over the naturals
[a#(x1)] = 1 + 1 · x1
[a(x1)] = 1 + 1 · x1
[b(x1)] = 1 + 1 · x1
[b#(x1)] = 1 · x1
the pairs
a#(a(a(a(x1)))) b#(a(b(x1))) (6)
a#(a(a(a(x1)))) a#(b(x1)) (7)
a#(a(a(a(x1)))) b#(x1) (8)
b#(b(a(b(x1)))) b#(b(b(x1))) (10)
b#(b(a(b(x1)))) b#(b(x1)) (11)
a#(a(a(b(x1)))) b#(a(b(b(x1)))) (12)
a#(a(a(b(x1)))) a#(b(b(x1))) (13)
a#(a(a(b(x1)))) b#(b(x1)) (14)
b#(a(b(b(x1)))) b#(a(x1)) (17)
b#(a(b(b(x1)))) a#(x1) (18)
could be deleted.

1.1.1 Dependency Graph Processor

The dependency pairs are split into 2 components.