Certification Problem

Input (TPDB SRS_Standard/Secret_06_SRS/secr1)

The rewrite relation of the following TRS is considered.

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

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by matchbox @ termCOMP 2023)

1 String Reversal

Since only unary symbols occur, one can reverse all terms and obtains the TRS
b(a(x1)) → b(b(b(b(x1)))) (5)
a(b(x1)) → a(a(a(a(x1)))) (6)
a(x1) → x1 (3)
b(x1) → x1 (4)

1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
b#(a(x1)) → b#(x1) (7)
b#(a(x1)) → b#(b(x1)) (8)
b#(a(x1)) → b#(b(b(x1))) (9)
b#(a(x1)) → b#(b(b(b(x1)))) (10)
a#(b(x1)) → a#(x1) (11)
a#(b(x1)) → a#(a(x1)) (12)
a#(b(x1)) → a#(a(a(x1))) (13)
a#(b(x1)) → a#(a(a(a(x1)))) (14)

1.1.1 Dependency Graph Processor

The dependency pairs are split into 2 components.