Agent strands in the action language nC+nC+

The action language C+C+ of Giunchiglia, Lee, Lifschitz, McCain and Turner is a formalism for specifying and reasoning about the effects of actions and the persistence (‘inertia’) of facts over time. An ‘action description’ in C+C+ defines a labelled transition system of a certain kind. nC+nC+ is an extended form of C+C+ designed for representing normative and institutional aspects of (human or computer) societies. The deontic component of nC+nC+ provides a means of specifying the permitted (acceptable, legal) states of a transition system and its permitted (acceptable, legal) transitions. We present this component of nC+nC+, motivating its details with reference to some small illustrative examples, and elaborate the formalism by allowing scope for norms governing individual agents. We describe the various kinds of investigation possible on the semantic structures which nC+nC+ defines.