Certification Problem

Input (TPDB SRS_Relative/Mixed_relative_SRS/zr03)

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

a(a(x1)) a(b(a(x1))) (1)

and S is the following TRS.

b(x1) b(b(x1)) (2)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 Semantic Labeling

Root-labeling is applied.

We obtain the labeled TRS
aa(aa(x1)) ab(ba(aa(x1))) (3)
aa(ab(x1)) ab(ba(ab(x1))) (4)
ba(x1) bb(ba(x1)) (5)
bb(x1) bb(bb(x1)) (6)

1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[aa(x1)] = 1 + 1 · x1
[ab(x1)] = 1 · x1
[ba(x1)] = 1 · x1
[bb(x1)] = 1 · x1
all of the following rules can be deleted.
aa(aa(x1)) ab(ba(aa(x1))) (3)
aa(ab(x1)) ab(ba(ab(x1))) (4)

1.1.1 R is empty

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