Certification Problem

Input (TPDB SRS_Standard/Zantema_04/z111)

The rewrite relation of the following TRS is considered.

a(a(x1)) b(c(c(c(x1)))) (1)
b(c(x1)) d(d(d(d(x1)))) (2)
a(x1) d(c(d(x1))) (3)
b(b(x1)) c(c(c(x1))) (4)
c(c(x1)) d(d(d(x1))) (5)
c(d(d(x1))) a(x1) (6)

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
[a(x1)] = 1 · x1 + 25
[b(x1)] = 1 · x1 + 17
[c(x1)] = 1 · x1 + 11
[d(x1)] = 1 · x1 + 7
all of the following rules can be deleted.
b(b(x1)) c(c(c(x1))) (4)
c(c(x1)) d(d(d(x1))) (5)

1.1 Dependency Pair Transformation

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

1.1.1 Dependency Graph Processor

The dependency pairs are split into 1 component.