Introduction

In order to meet the desiderata for a UIA discussed in Section 1.4, a UIA needs to reason about time as well as actions and their effects. Representing and reasoning about time, actions, effects and temporal relationships have been widely studied both in the areas of philosophy and artificial intelligence. The next sections examine (i) some of the issues associated with representing and reasoning about time (ii) some of the issues associated with representing and reasoning about actions, effects and temporal relationships and (iii) some of the formal frameworks discussed in the literature and how they deal with some of these issues.