Example 2: Goal introduction problem

This section describes a practical problem that can be encountered in customer service dialogues. The problem is that of deciding to add a goal to the dialogue plan. Like the first example it is a problem of initiative, since either the first agent or the second agent could be the one to add the goal. The problem is one that is familiar to patrons of fast-food restaurants, where the customer initiates the dialogue by placing an order. In response, the agent might add new goals, like offering fries or a drink. This would be a valuable initiative if the customer were not aware that such things were available for sale, but would buy them if they were. On the other hand, it would be less valuable if most customers knew what was for sale, and rarely wanted anything other than a hamburger. Another example is at an airport check-in, where a customer may not believe that a window seat is available, and so may not waste time asking for one. On the other hand, the agent may believe that most customers do not want a window seat and so may not waste time offering one. This problem is again one of choosing between the riskier alternative of introducing a goal that might fail, and the less risky one of passing the initiative to the other agent. It is also a symmetrical problem since both agents make risky decisions in introducing the goal.

A plan library has been constructed for the window seat problem. This is described in figure 4.14. Notice that the first agent can begin with a goal of getting a window seat, or of getting any seat. The second agent can respond by taking the initiative and offering one directly, or it can drop the initiative and move with a pleasant chat about something else. There is a precondition to offering that the agent believes that it has an available seat. If the second agent takes the latter alternative, the first agent then has the option to pick up the initiative by asking for a window seat, or drop it and move instead with a pleasant chat about something else. If it asks, then, if the second agent's precondition of having a seat is satisfied, it will give the first agent a window seat.

Figure 4.14: Plan library for goal introduction problem

From this plan library, the planner produces the game tree described in figure 4.15. Notice that in this tree the bel(have-seat) precondition causes the introduction of a chance node that determines whether the agent can offer. The have-seat precondition determines whether it can give. ask and accept only occur if the agent intended book-flight-window. Therefore a chance node is introduced before these acts. This chance node is generated by the parent intention rules.

Figure 4.15: Game tree for the goal introduction problem