Let us now consider some more examples in which our interval arithmetic approach can be shown to be useful and valid. We begin with a simple example. Suppose we have two relational fluents P, and Q, and that we know P is true or we know Q is true:
Proof. The proof is straightforward: We don’t know P if in at least one of the K-related worlds P is false.
So, if P is false in all the K-related worlds the result follows. We just have to be careful that there are any