Certification Problem

Input (TPDB SRS_Standard/Secret_06_SRS/secr6)

The rewrite relation of the following TRS is considered.

a(b(c(x1))) → c(c(c(b(b(b(a(a(a(x1))))))))) (1)
c(b(x1)) → a(a(a(x1))) (2)
a(x1) → x1 (3)
b(x1) → x1 (4)
c(x1) → x1 (5)

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
c(b(a(x1))) → a(a(a(b(b(b(c(c(c(x1))))))))) (6)
b(c(x1)) → a(a(a(x1))) (7)
a(x1) → x1 (3)
b(x1) → x1 (4)
c(x1) → x1 (5)

1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
c#(b(a(x1))) → c#(x1) (8)
c#(b(a(x1))) → c#(c(x1)) (9)
c#(b(a(x1))) → c#(c(c(x1))) (10)
c#(b(a(x1))) → b#(c(c(c(x1)))) (11)
c#(b(a(x1))) → b#(b(c(c(c(x1))))) (12)
c#(b(a(x1))) → b#(b(b(c(c(c(x1)))))) (13)
c#(b(a(x1))) → a#(b(b(b(c(c(c(x1))))))) (14)
c#(b(a(x1))) → a#(a(b(b(b(c(c(c(x1)))))))) (15)
c#(b(a(x1))) → a#(a(a(b(b(b(c(c(c(x1))))))))) (16)
b#(c(x1)) → a#(x1) (17)
b#(c(x1)) → a#(a(x1)) (18)
b#(c(x1)) → a#(a(a(x1))) (19)

1.1.1 Monotonic Reduction Pair Processor with Usable Rules

Using the matrix interpretations of dimension 1 with strict dimension 1 over the rationals with delta = 1
[c(x1)] = x1 +
0
[b(x1)] = x1 +
0
[a(x1)] = x1 +
0
[c#(x1)] = x1 +
2
[b#(x1)] = x1 +
1
[a#(x1)] = x1 +
0
together with the usable rules
c(b(a(x1))) → a(a(a(b(b(b(c(c(c(x1))))))))) (6)
b(c(x1)) → a(a(a(x1))) (7)
a(x1) → x1 (3)
b(x1) → x1 (4)
c(x1) → x1 (5)
(w.r.t. the implicit argument filter of the reduction pair), the pairs
c#(b(a(x1))) → b#(c(c(c(x1)))) (11)
c#(b(a(x1))) → b#(b(c(c(c(x1))))) (12)
c#(b(a(x1))) → b#(b(b(c(c(c(x1)))))) (13)
c#(b(a(x1))) → a#(b(b(b(c(c(c(x1))))))) (14)
c#(b(a(x1))) → a#(a(b(b(b(c(c(c(x1)))))))) (15)
c#(b(a(x1))) → a#(a(a(b(b(b(c(c(c(x1))))))))) (16)
b#(c(x1)) → a#(x1) (17)
b#(c(x1)) → a#(a(x1)) (18)
b#(c(x1)) → a#(a(a(x1))) (19)
and no rules could be deleted.

1.1.1.1 Dependency Graph Processor

The dependency pairs are split into 1 component.