Certification Problem

Input (TPDB SRS_Standard/Waldmann_19/random-332)

The rewrite relation of the following TRS is considered.

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

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 String Reversal

Since only unary symbols occur, one can reverse all terms and obtains the TRS
b(a(a(b(x1)))) → a(b(a(b(x1)))) (5)
a(a(a(b(x1)))) → b(b(a(b(x1)))) (6)
b(a(b(a(x1)))) → b(b(b(b(x1)))) (7)
b(a(b(a(x1)))) → b(a(a(a(x1)))) (8)

1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
b#(a(a(b(x1)))) → a#(b(a(b(x1)))) (9)
b#(a(a(b(x1)))) → b#(a(b(x1))) (10)
a#(a(a(b(x1)))) → b#(b(a(b(x1)))) (11)
a#(a(a(b(x1)))) → b#(a(b(x1))) (12)
b#(a(b(a(x1)))) → b#(b(b(b(x1)))) (13)
b#(a(b(a(x1)))) → b#(b(b(x1))) (14)
b#(a(b(a(x1)))) → b#(b(x1)) (15)
b#(a(b(a(x1)))) → b#(x1) (16)
b#(a(b(a(x1)))) → b#(a(a(a(x1)))) (17)
b#(a(b(a(x1)))) → a#(a(a(x1))) (18)
b#(a(b(a(x1)))) → a#(a(x1)) (19)

1.1.1 Reduction Pair Processor

Using the linear polynomial interpretation over the naturals
[b#(x1)] = 1 + 1 · x1
[a(x1)] = 1 + 1 · x1
[b(x1)] = 1 + 1 · x1
[a#(x1)] = 1 + 1 · x1
the pairs
b#(a(a(b(x1)))) → b#(a(b(x1))) (10)
a#(a(a(b(x1)))) → b#(a(b(x1))) (12)
b#(a(b(a(x1)))) → b#(b(b(x1))) (14)
b#(a(b(a(x1)))) → b#(b(x1)) (15)
b#(a(b(a(x1)))) → b#(x1) (16)
b#(a(b(a(x1)))) → a#(a(a(x1))) (18)
b#(a(b(a(x1)))) → a#(a(x1)) (19)
could be deleted.

1.1.1.1 Reduction Pair Processor

Using the matrix interpretations of dimension 3 with strict dimension 1 over the arctic semiring over the naturals
[b#(x1)] =
0
-∞
-∞
+
0 0 0
-∞ -∞ -∞
-∞ -∞ -∞
· x1
[a(x1)] =
0
0
0
+
-∞ 0 0
0 -∞ -∞
0 1 0
· x1
[b(x1)] =
0
-∞
0
+
0 1 1
-∞ 0 0
-∞ 0 0
· x1
[a#(x1)] =
1
-∞
-∞
+
0 0 1
-∞ -∞ -∞
-∞ -∞ -∞
· x1
the pair
a#(a(a(b(x1)))) → b#(b(a(b(x1)))) (11)
could be deleted.

1.1.1.1.1 Dependency Graph Processor

The dependency pairs are split into 1 component.