Variables in Action Descriptions: Merging C+ with ADL

Action description language C+ is more expressive than ADL in many ways; for instance, it addresses the ramification problem. On the other hand, ADL is based on first-order logic, while C+ is only propositional; expressions with variables, which are frequently used when action domains are described in C+, are merely schemas describing finite sets of causal laws that are formed according to the same pattern. In this paper we propose a new approach to the semantics of action descriptions with variables that combines attractive features of ADL and C+.