Certification Problem

Input (TPDB TRS_Standard/SK90/4.52)

The rewrite relation of the following TRS is considered.

s(a) a (1)
s(s(x)) x (2)
s(f(x,y)) f(s(y),s(x)) (3)
s(g(x,y)) g(s(x),s(y)) (4)
f(x,a) x (5)
f(a,y) y (6)
f(g(x,y),g(u,v)) g(f(x,u),f(y,v)) (7)
g(a,a) a (8)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by NaTT @ termCOMP 2023)

1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
f#(g(x,y),g(u,v)) f#(x,u) (9)
s#(f(x,y)) s#(x) (10)
s#(g(x,y)) s#(y) (11)
s#(g(x,y)) g#(s(x),s(y)) (12)
s#(f(x,y)) s#(y) (13)
f#(g(x,y),g(u,v)) f#(y,v) (14)
f#(g(x,y),g(u,v)) g#(f(x,u),f(y,v)) (15)
s#(g(x,y)) s#(x) (16)
s#(f(x,y)) f#(s(y),s(x)) (17)

1.1 Dependency Graph Processor

The dependency pairs are split into 2 components.