Certification Problem
Input (COPS 374)
The rewrite relation of the following conditional TRS is considered.
| a |
→ |
c |
| a |
→ |
d |
|
f(x,y) |
→ |
z |
| c ≈ x, y ≈ z
|
Property / Task
Prove or disprove confluence.Answer / Result
No.Proof (by ConCon @ CoCo 2020)
1 Inlining of Conditions
Inlining of conditions results in the following transformed CTRS having the
same multistep rewrite relation.
| a |
→ |
c |
| a |
→ |
d |
|
f(x,y) |
→ |
y |
| c ≈ x
|
1.1 Non-Joinable Fork
The system is not confluent due to the following forking derivations.
The two resulting terms cannot be joined for the following reason:
- When applying the cap-function on both terms (where variables may be treated like constants)
then the resulting terms do not unify.