Certification Problem

Input (TPDB SRS_Standard/Waldmann_19/random-355)

The rewrite relation of the following TRS is considered.

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

1.1 Semantic Labeling

Root-labeling is applied.

We obtain the labeled TRS
aa(ab(ba(aa(x1)))) → aa(aa(ab(ba(x1)))) (6)
aa(ab(ba(ab(x1)))) → aa(aa(ab(bb(x1)))) (7)
ba(aa(ab(ba(x1)))) → bb(bb(ba(aa(x1)))) (8)
ba(aa(ab(bb(x1)))) → bb(bb(ba(ab(x1)))) (9)
ab(bb(bb(ba(aa(x1))))) → aa(aa(aa(ab(ba(x1))))) (10)
ab(bb(bb(ba(ab(x1))))) → aa(aa(aa(ab(bb(x1))))) (11)
bb(bb(bb(ba(aa(x1))))) → ba(aa(aa(ab(ba(x1))))) (12)
bb(bb(bb(ba(ab(x1))))) → ba(aa(aa(ab(bb(x1))))) (13)

1.1.1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
aa#(ab(ba(aa(x1)))) → aa#(aa(ab(ba(x1)))) (14)
aa#(ab(ba(aa(x1)))) → aa#(ab(ba(x1))) (15)
aa#(ab(ba(aa(x1)))) → ab#(ba(x1)) (16)
aa#(ab(ba(aa(x1)))) → ba#(x1) (17)
aa#(ab(ba(ab(x1)))) → aa#(aa(ab(bb(x1)))) (18)
aa#(ab(ba(ab(x1)))) → aa#(ab(bb(x1))) (19)
aa#(ab(ba(ab(x1)))) → ab#(bb(x1)) (20)
aa#(ab(ba(ab(x1)))) → bb#(x1) (21)
ba#(aa(ab(ba(x1)))) → bb#(bb(ba(aa(x1)))) (22)
ba#(aa(ab(ba(x1)))) → bb#(ba(aa(x1))) (23)
ba#(aa(ab(ba(x1)))) → ba#(aa(x1)) (24)
ba#(aa(ab(ba(x1)))) → aa#(x1) (25)
ba#(aa(ab(bb(x1)))) → bb#(bb(ba(ab(x1)))) (26)
ba#(aa(ab(bb(x1)))) → bb#(ba(ab(x1))) (27)
ba#(aa(ab(bb(x1)))) → ba#(ab(x1)) (28)
ba#(aa(ab(bb(x1)))) → ab#(x1) (29)
ab#(bb(bb(ba(aa(x1))))) → aa#(aa(aa(ab(ba(x1))))) (30)
ab#(bb(bb(ba(aa(x1))))) → aa#(aa(ab(ba(x1)))) (31)
ab#(bb(bb(ba(aa(x1))))) → aa#(ab(ba(x1))) (32)
ab#(bb(bb(ba(aa(x1))))) → ab#(ba(x1)) (33)
ab#(bb(bb(ba(aa(x1))))) → ba#(x1) (34)
ab#(bb(bb(ba(ab(x1))))) → aa#(aa(aa(ab(bb(x1))))) (35)
ab#(bb(bb(ba(ab(x1))))) → aa#(aa(ab(bb(x1)))) (36)
ab#(bb(bb(ba(ab(x1))))) → aa#(ab(bb(x1))) (37)
ab#(bb(bb(ba(ab(x1))))) → ab#(bb(x1)) (38)
ab#(bb(bb(ba(ab(x1))))) → bb#(x1) (39)
bb#(bb(bb(ba(aa(x1))))) → ba#(aa(aa(ab(ba(x1))))) (40)
bb#(bb(bb(ba(aa(x1))))) → aa#(aa(ab(ba(x1)))) (41)
bb#(bb(bb(ba(aa(x1))))) → aa#(ab(ba(x1))) (42)
bb#(bb(bb(ba(aa(x1))))) → ab#(ba(x1)) (43)
bb#(bb(bb(ba(aa(x1))))) → ba#(x1) (44)
bb#(bb(bb(ba(ab(x1))))) → ba#(aa(aa(ab(bb(x1))))) (45)
bb#(bb(bb(ba(ab(x1))))) → aa#(aa(ab(bb(x1)))) (46)
bb#(bb(bb(ba(ab(x1))))) → aa#(ab(bb(x1))) (47)
bb#(bb(bb(ba(ab(x1))))) → ab#(bb(x1)) (48)
bb#(bb(bb(ba(ab(x1))))) → bb#(x1) (49)

1.1.1.1 Dependency Graph Processor

The dependency pairs are split into 1 component.