Suspending and resuming tasks in BDI agents

Intelligent agents designed to work in complex, dynamic environments must respond robustly and flexibly to environmental and circumstantial changes. An agent must be capable of deliberating about appropriate courses of action, which may include reprioritising goals, aborting particular tasks, or scheduling tasks in a particular order. This paper investigates the incorporation of a mechanism to suspend and reconsider tasks within a BDI-style architecture. Such an ability provides an agent designer greater flexibility to direct agent operation, and it offers a generic means for handling conflicts between tasks. We investigate conditions under which a goal or a plan may be suspended, the process for suspending it, and the appropriate behaviours upon resumption. We give an operational semantics for suspending tasks in terms of the abstract agent language CAN, thus providing a general mechanism that can be incorporated into any BDI-based agent programming language.