Certification Problem

Input (COPS 103)

We consider the TRS containing the following rules:

f(f(x,y),z) f(x,f(y,z)) (1)
f(x,y) f(y,x) (2)

The underlying signature is as follows:

{f/2}

Property / Task

Prove or disprove confluence.

Answer / Result

Yes.

Proof (by csi @ CoCo 2023)

1 Redundant Rules Transformation

To prove that the TRS is (non-)confluent, we show (non-)confluence of the following modified system:

f(x,y) f(y,x) (2)
f(f(x,y),z) f(x,f(y,z)) (1)
f(x,y) f(x,y) (3)
f(f(x,y),z) f(x,f(z,y)) (4)
f(f(x,y),z) f(f(y,z),x) (5)

All redundant rules that were added or removed can be simulated in 2 steps .

1.1 Strongly closed

Confluence is proven since the TRS is strongly closed. The joins can be performed using 7 step(s).