The need to represent actions arises in many different areas of investigation, such as philosophy [5], semantics [10], and planning. In the first two areas, representations are generally developed without any computational concerns. The third area sees action representation mainly as functional to the more general task of reaching a certain goal: actions have often been represented by a predicate with some arguments, such as move(John, block1, room1, room2), augmented with a description of its effects and of what has to be true in the world for the action to be executable [8]. .
