Certification Problem

Input (TPDB SRS_Relative/Mixed_relative_SRS/zr11)

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

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

and S is the following TRS.

b(x1) → c(b(x1)) (3)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by ttt2 @ termCOMP 2023)

1 String Reversal

Since only unary symbols occur, one can reverse all terms and obtains the TRS
a(c(b(x1))) → b(a(b(a(x1)))) (4)
a(a(x1)) → a(b(c(a(x1)))) (5)
b(x1) → b(c(x1)) (6)

1.1 Rule Removal

Using the linear polynomial interpretation over (3 x 3)-matrices with strict dimension 1 over the naturals
[c(x1)] =
1 0 1
0 0 1
0 0 0
· x1 +
0 0 0
0 0 0
0 0 0
[a(x1)] =
1 1 0
0 1 0
0 1 0
· x1 +
0 0 0
0 0 0
0 0 0
[b(x1)] =
1 0 1
0 0 0
0 1 1
· x1 +
0 0 0
0 0 0
1 0 0
all of the following rules can be deleted.
a(c(b(x1))) → b(a(b(a(x1)))) (4)

1.1.1 Rule Removal

Using the linear polynomial interpretation over (3 x 3)-matrices with strict dimension 1 over the naturals
[c(x1)] =
1 0 0
1 0 1
0 0 1
· x1 +
0 0 0
1 0 0
0 0 0
[a(x1)] =
1 1 1
1 1 0
0 1 0
· x1 +
0 0 0
1 0 0
1 0 0
[b(x1)] =
1 0 1
0 0 0
0 0 0
· x1 +
0 0 0
0 0 0
0 0 0
all of the following rules can be deleted.
a(a(x1)) → a(b(c(a(x1)))) (5)

1.1.1.1 R is empty

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