Certification Problem

Input (TPDB SRS_Standard/Waldmann_19/random-244)

The rewrite relation of the following TRS is considered.

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

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 Closure Under Flat Contexts

Using the flat contexts

{a(☐), b(☐)}

We obtain the transformed TRS
a(a(b(a(x1)))) → a(b(a(b(x1)))) (1)
a(b(b(a(b(x1))))) → a(a(b(b(a(x1))))) (4)
b(b(b(a(b(x1))))) → b(a(b(b(a(x1))))) (5)
a(b(b(a(b(x1))))) → a(a(a(a(a(x1))))) (6)
b(b(b(a(b(x1))))) → b(a(a(a(a(x1))))) (7)

1.1 Semantic Labeling

Root-labeling is applied.

We obtain the labeled TRS
aa(ab(ba(aa(x1)))) → ab(ba(ab(ba(x1)))) (8)
aa(ab(ba(ab(x1)))) → ab(ba(ab(bb(x1)))) (9)
ab(bb(ba(ab(ba(x1))))) → aa(ab(bb(ba(aa(x1))))) (10)
ab(bb(ba(ab(bb(x1))))) → aa(ab(bb(ba(ab(x1))))) (11)
bb(bb(ba(ab(ba(x1))))) → ba(ab(bb(ba(aa(x1))))) (12)
bb(bb(ba(ab(bb(x1))))) → ba(ab(bb(ba(ab(x1))))) (13)
ab(bb(ba(ab(ba(x1))))) → aa(aa(aa(aa(aa(x1))))) (14)
ab(bb(ba(ab(bb(x1))))) → aa(aa(aa(aa(ab(x1))))) (15)
bb(bb(ba(ab(ba(x1))))) → ba(aa(aa(aa(aa(x1))))) (16)
bb(bb(ba(ab(bb(x1))))) → ba(aa(aa(aa(ab(x1))))) (17)

1.1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
aa#(ab(ba(aa(x1)))) → ab#(ba(ab(ba(x1)))) (18)
aa#(ab(ba(aa(x1)))) → ab#(ba(x1)) (19)
aa#(ab(ba(ab(x1)))) → ab#(ba(ab(bb(x1)))) (20)
aa#(ab(ba(ab(x1)))) → ab#(bb(x1)) (21)
aa#(ab(ba(ab(x1)))) → bb#(x1) (22)
ab#(bb(ba(ab(ba(x1))))) → aa#(ab(bb(ba(aa(x1))))) (23)
ab#(bb(ba(ab(ba(x1))))) → ab#(bb(ba(aa(x1)))) (24)
ab#(bb(ba(ab(ba(x1))))) → bb#(ba(aa(x1))) (25)
ab#(bb(ba(ab(ba(x1))))) → aa#(x1) (26)
ab#(bb(ba(ab(bb(x1))))) → aa#(ab(bb(ba(ab(x1))))) (27)
ab#(bb(ba(ab(bb(x1))))) → ab#(bb(ba(ab(x1)))) (28)
ab#(bb(ba(ab(bb(x1))))) → bb#(ba(ab(x1))) (29)
ab#(bb(ba(ab(bb(x1))))) → ab#(x1) (30)
bb#(bb(ba(ab(ba(x1))))) → ab#(bb(ba(aa(x1)))) (31)
bb#(bb(ba(ab(ba(x1))))) → bb#(ba(aa(x1))) (32)
bb#(bb(ba(ab(ba(x1))))) → aa#(x1) (33)
bb#(bb(ba(ab(bb(x1))))) → ab#(bb(ba(ab(x1)))) (34)
bb#(bb(ba(ab(bb(x1))))) → bb#(ba(ab(x1))) (35)
bb#(bb(ba(ab(bb(x1))))) → ab#(x1) (36)
ab#(bb(ba(ab(ba(x1))))) → aa#(aa(aa(aa(aa(x1))))) (37)
ab#(bb(ba(ab(ba(x1))))) → aa#(aa(aa(aa(x1)))) (38)
ab#(bb(ba(ab(ba(x1))))) → aa#(aa(aa(x1))) (39)
ab#(bb(ba(ab(ba(x1))))) → aa#(aa(x1)) (40)
ab#(bb(ba(ab(bb(x1))))) → aa#(aa(aa(aa(ab(x1))))) (41)
ab#(bb(ba(ab(bb(x1))))) → aa#(aa(aa(ab(x1)))) (42)
ab#(bb(ba(ab(bb(x1))))) → aa#(aa(ab(x1))) (43)
ab#(bb(ba(ab(bb(x1))))) → aa#(ab(x1)) (44)
bb#(bb(ba(ab(ba(x1))))) → aa#(aa(aa(aa(x1)))) (45)
bb#(bb(ba(ab(ba(x1))))) → aa#(aa(aa(x1))) (46)
bb#(bb(ba(ab(ba(x1))))) → aa#(aa(x1)) (47)
bb#(bb(ba(ab(bb(x1))))) → aa#(aa(aa(ab(x1)))) (48)
bb#(bb(ba(ab(bb(x1))))) → aa#(aa(ab(x1))) (49)
bb#(bb(ba(ab(bb(x1))))) → aa#(ab(x1)) (50)

1.1.1.1 Dependency Graph Processor

The dependency pairs are split into 1 component.