Certification Problem

Input (TPDB TRS_Relative/Relative_05/rt1-5)

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

s(a(x)) s(b(x)) (1)
b(b(x)) a(x) (2)

and S is the following TRS.

f(s(x),y) f(x,s(y)) (3)
s(b(x)) b(s(x)) (4)
b(s(x)) s(b(x)) (5)
s(a(x)) a(s(x)) (6)
a(s(x)) s(a(x)) (7)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 Rule Removal

Using the linear polynomial interpretation over the naturals
[s(x1)] = 1 · x1
[a(x1)] = 1 + 1 · x1
[b(x1)] = 1 + 1 · x1
[f(x1, x2)] = 1 · x1 + 1 · x2
all of the following rules can be deleted.
b(b(x)) a(x) (2)

1.1 Rule Removal

Using the linear polynomial interpretation over the naturals
[s(x1)] = 1 · x1
[a(x1)] = 1 + 1 · x1
[b(x1)] = 1 · x1
[f(x1, x2)] = 1 · x1 + 1 · x2
all of the following rules can be deleted.
s(a(x)) s(b(x)) (1)

1.1.1 R is empty

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