Certification Problem

Input (TPDB SRS_Standard/Secret_05_SRS/aprove5)

The rewrite relation of the following TRS is considered.

a(b(x1)) → b(c(a(x1))) (1)
b(c(x1)) → c(b(b(x1))) (2)
a(c(x1)) → c(a(b(x1))) (3)
a(a(x1)) → a(d(d(d(x1)))) (4)
d(a(x1)) → d(d(c(x1))) (5)
a(d(d(c(x1)))) → a(a(a(d(x1)))) (6)
e(e(f(f(x1)))) → f(f(f(e(e(x1))))) (7)
e(x1) → a(x1) (8)
b(d(x1)) → d(d(x1)) (9)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by matchbox @ termCOMP 2023)

1 Rule Removal

Using the matrix interpretations of dimension 1 with strict dimension 1 over the rationals with delta = 1
[f(x1)] = x1 +
0
[e(x1)] = x1 +
1
[d(x1)] = x1 +
0
[c(x1)] = x1 +
0
[b(x1)] = x1 +
0
[a(x1)] = x1 +
0
all of the following rules can be deleted.
e(x1) → a(x1) (8)

1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
e#(e(f(f(x1)))) → e#(x1) (10)
e#(e(f(f(x1)))) → e#(e(x1)) (11)
d#(a(x1)) → d#(d(c(x1))) (12)
d#(a(x1)) → d#(c(x1)) (13)
b#(d(x1)) → d#(d(x1)) (14)
b#(c(x1)) → b#(x1) (15)
b#(c(x1)) → b#(b(x1)) (16)
a#(d(d(c(x1)))) → d#(x1) (17)
a#(d(d(c(x1)))) → a#(d(x1)) (18)
a#(d(d(c(x1)))) → a#(a(d(x1))) (19)
a#(d(d(c(x1)))) → a#(a(a(d(x1)))) (20)
a#(c(x1)) → b#(x1) (21)
a#(c(x1)) → a#(b(x1)) (22)
a#(b(x1)) → b#(c(a(x1))) (23)
a#(b(x1)) → a#(x1) (24)
a#(a(x1)) → d#(x1) (25)
a#(a(x1)) → d#(d(x1)) (26)
a#(a(x1)) → d#(d(d(x1))) (27)
a#(a(x1)) → a#(d(d(d(x1)))) (28)

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
[f(x1)] = x1 +
0
[e(x1)] = x1 +
2
[d(x1)] = x1 +
0
[c(x1)] = x1 +
0
[b(x1)] = x1 +
0
[a(x1)] = x1 +
0
[e#(x1)] = x1 +
0
[d#(x1)] = x1 +
0
[b#(x1)] = x1 +
1
[a#(x1)] = x1 +
2
together with the usable rules
a(b(x1)) → b(c(a(x1))) (1)
b(c(x1)) → c(b(b(x1))) (2)
a(c(x1)) → c(a(b(x1))) (3)
a(a(x1)) → a(d(d(d(x1)))) (4)
d(a(x1)) → d(d(c(x1))) (5)
a(d(d(c(x1)))) → a(a(a(d(x1)))) (6)
e(e(f(f(x1)))) → f(f(f(e(e(x1))))) (7)
b(d(x1)) → d(d(x1)) (9)
(w.r.t. the implicit argument filter of the reduction pair), the pairs
e#(e(f(f(x1)))) → e#(x1) (10)
b#(d(x1)) → d#(d(x1)) (14)
a#(d(d(c(x1)))) → d#(x1) (17)
a#(c(x1)) → b#(x1) (21)
a#(b(x1)) → b#(c(a(x1))) (23)
a#(a(x1)) → d#(x1) (25)
a#(a(x1)) → d#(d(x1)) (26)
a#(a(x1)) → d#(d(d(x1))) (27)
and no rules could be deleted.

1.1.1.1 Dependency Graph Processor

The dependency pairs are split into 3 components.