An Action Language for Dynamic Systems of Class C2 in Knowledge Representation and Reasoning

1 DESCRIPTION OF C2 Dynamic systems of class C2 satisfy the following assumptions: • Inertia law. • Complete information about all actions and fluents. • Non-determinism • Only sequential actions are allowed. • Characterizations of actions: – precondition (a propositional formula); if a precondition does not hold, the action is executed, but with empty effect. – postcondition (effect of an action, represented by a propositional formula) – time t ∈ N required for an action to be performed; assume that it depends only on a state where the action starts. • In some states (specified by a propositional formula) some actions cannot be performed. • Partial descriptions of any state of the system are allowed. • Constraint conditions influence only qualifications of actions. A program is a sequence (A1 ,...,An ) of actions. 2 TASK Define an action description language ADLC2 for representing dynamic systems of the class specified in the previous section, and define the corresponding query language QLC2 , which allows us to get answers for the following queries: Q1. Can a given program always/ever be executed during at most t time units? Q2. Does a given condition α hold always/ever after performing a given program in an initial state?