Complex Plans in the Fluent Calculus

Abstract

Imagine an autonomous agent performing a task in the real world. Its performance is based on an internal plan. From a low level point of view, the world is its own representation and the actions of the aforementioned plan are simple commands controlling the effectors of the agent. At a higher level of abstraction, the world is internally represented by states and (primitive) actions are transformations on the space of states. In this article we do not want to discuss how actions on the higher level lead to commands on the lower level or whether the abstract level is needed or not, although these are very interesting and active open research problems. We also do not want to deal with another burning question of how the agent got hold of its plan. The plan may be given to it by a programmer, it may have (semi-)automatically generated the plan from the initial state, the goal state and the descriptions of the primitive actions it is able to perform or it may have learned it from examples. For the purpose of this article we just assume that a plan at the abstract level is given.