# An Abductive Event Calculus Planner

# Murray Shanahan

## Abstract

In 1969 Cordell Green presented his seminal description of planning as
theorem proving with the situation calculus. The most pleasing feature of
Green's account was the negligible gap between high-level logical
specification and practical implementation. This paper attempts to
reinstate the ideal of planning via theorem proving in a modern guise. In
particular, the paper shows that if we adopt the event calculus as our
logical formalism and employ abductive logic programming as our theorem
proving technique, then the computation performed mirrors closely that of
a hand-coded partial-order planning algorithm. Soundness and completeness
results for this logic programming implementation are given. Finally the
paper shows that, if we extend the event calculus in a natural way to
accommodate compound actions, then using the same abductive theorem
proving techniques we can obtain a hierarchical planner.