addition to providing the results for the particular team coordination strategies investigated, this section also illustrates a general methodology by which one can use our COM-MTDP framework to encode and evaluate coordination strategies proposed by existing multiagent research.

## 4.1 Joint Intentions In A Com-Mtdp

Joint intention theory provides a prescriptive framework for multiagent coordination in a team setting. It does not make any claims of optimality in its teamwork, but it provides theoretical justifications for its prescriptions, grounded in the attainment of mutual belief among the team members. We can use the COM-MTDP framework to identify the domain properties under which attaining mutual belief generates optimal behavior and to quantify precisely how suboptimal the performance will be otherwise.

Joint intentions theory requires that team members jointly commit to a joint persistent goal, G. It also requires that when any team member privately believes that G is achieved (or unachievable or irrelevant), it must then attain mutual belief throughout the team about this aievement (or unaievability or irrelevance). To encode this prescription of joint intentions theory within our COM-MTDP model, we first specify the joint goal, G, as a subset of states, G ⊆ S, where the desired goal is achieved (or unachievable or irrelevant).

Presumably, such a prescription indicates that joint intentions are not specifically intended for individually observable environments. Upon achieving the goal in an individually observable environment, each agent would simultaneously observe that S t ∈ G. Because of our assumption that the COM-MTDP model components (including O a ) are common knowledge to the team, each agent would also simultaneously come to believe that its teammates have observed that S t ∈ G , and that its teammates believe that it believes that all of the team members have observed that S t ∈ G t and so on. Thus, the team immediately attains mutual belief in the achievement of the goal under individual observability without any additional communication necessary by the team.

Instead, the joint intention framework aims at domains with some degree of unobservability. In such domains, the agents must signal the other agents, either through communication or some informative domain-level action, to attain mutual belief. However, we can also assume that joint intention theory does not focus on domains with free communication, where Theorem 2 shows that we can simply have the agents communicate everything, all the time, without the need for more complex prescriptions.

The joint intention framework does not specify a precise communication policy for the attainment of mutual belief. In this paper, we focus on communication only in the case of goal achievement, but our methodology extends to handle unachievability and irrelevance as well.  One well-known approach (Jennings, 1995) applied joint intentions theory by having the agents communicate the achievement of the joint goal, G, as soon as they believe G to be true. To instantiate the behavior of Jennings' agents within a COM-MTDP, we construct a communication policy, 7 ax, that specifies that an agent sends the special message, σ G , when it first believes that G holds. Following joint intentions' assumption of sincerity (Smith & Cohen, 1996), we require that the agents never select the special σς message in a belief state unless they believe G to be true with certainty. With this requirement and with our assumption of the team's common knowledge of the communication model, we can assume