Being effective when suspending goals*

In their everyday lives people flexibly handle many tasks. They work on one at a time, make quick decisions about which one to work on, and put aside tasks whenever attending to them is not required to achieve the task’s goal. This last capability is critical because rather than fixate on a blocked task, a person can work on some other task. For example, a person making bean soup wouldn’t watch the beans as they soak overnight. Instead she would take the inability to affect the progress of making bean soup as an opportunity to work on some other, possibly less important task where progress is possible. When taking advantage of these opportunities, people don’t completely forget what they were doing. Instead, the put-aside tasks guide the selection of the new tasks. After the beans have soaked and the soup is simmering, a person might go out to get other chores done, but she probably would not forget the soup and eat out. By putting aside a blocked task and remembering it at the appropriate time, a person can complete many other tasks and still accomplish the blocked one in a timely manner. This paper describes how an artificial agent, called Laureli, can maintain goal-directed behavior while suspending her blocked tasks similarly to that described above. Laureli serves as an exemplar agent, grounding in detailed and understandable examples the problems that occur when she suspends her tasks for later reactivation. In creating Lautell, this paper extends work [Hammond, 1989; Pryor, 1994] done to recognize when a task is blocked so that it can be put aside until progress is possible again. Laureli’s suspension-reactivation mechanisms provide for interleaving more available tasks