Operational Behaviour for Executing, Suspending, and Aborting Goals in BDI Agent Systems

Deliberation over and management of goals is a key aspect of an agent's architecture. We consider the various types of goals studied in the literature, including performance, achievement, and maintenance goals. Focusing on BDI agents, we develop a detailed description of goal states (such as whether goals have been suspended or not) and a comprehensive suite of operations that may be applied to goals (including dropping, aborting, suspending and resuming them). We show how to specify an operational semantics corresponding to this detailed description in an abstract agent language (CAN). The three key contributions of our generic framework for goal states and transitions are (1) to encompass both goals of accomplishment and rich goals of monitoring, (2) to provide the first specification of abort and suspend for all the common goal types, and (3) to account for plan execution as well as the dynamics of sub-goaling.