These solutions are now grouped under the heading of chronological minimization, a term suggested by Shoham. Y. Shoham and D. McDermott. Problems in Formal Temporal Reasoning . We are not aware that they or their respective spatial counterparts have been explicitly addressed in the spatial reasoning literature. This enables them to reduce the complexity of their reasoning algorithm.
Some researchers use the term inertia instead of persistence.
Y. ShohamandD.V. McDermott. Problems in formal temporal reasoning . But , since discretization is always finite, a problem arises when an action or event takes place in between two of these points. Imagine further that these two balls will collide on their courses at a certain point of time. Now , if the discretization does not take into regard this very point of time then the collision is not detected and the balls seem to be moving on into their original directions, which results in entirely wrong final positions of the balls.