observational equivalence

Observational equivalence is a concept in computer science and logic that means two systems or programs behave identically from an external point of view. In other words, no matter how an observer interacts with or tests them, they produce the same observable results or outputs. This allows us to consider different implementations as essentially the same if their observable behaviors are indistinguishable, even if their inner workings differ. It’s a way of comparing systems based on how they appear and respond externally, rather than their internal structure or code.