Certification Problem

Input (COPS 177)

We consider the TRS containing the following rules:

-(+(x,y)) → +(-(x),-(y)) (1)
+(-(x),-(y)) → -(+(x,y)) (2)

The underlying signature is as follows:

{-/1, +/2}

Property / Task

Prove or disprove confluence.

Answer / Result

Yes.

Proof (by csi @ CoCo 2021)

1 Redundant Rules Transformation

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

+(-(x),-(y)) → -(+(x,y)) (2)
-(+(x,y)) → +(-(x),-(y)) (1)
+(-(x),-(y)) → +(-(x),-(y)) (3)
-(+(x,y)) → -(+(x,y)) (4)

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).