Joint Intention

1
Joint Intention

• A joint commitment to perform a collective action
  while in a certain shared mental state
• Assumptions
• Dynamic, multi-agent world
• Agents possessing neither complete nor correct
  beliefs
• Having changeable goals and fallible actions,
  subject to interruption from external event

2
Benefits of the Theory

• Show joint intentions lead to individual ones
• Specify how joint intentions affects the behavior
  of agents
• Induce needed communications

3
Convoy Example

• Bob wants to go to Virginia Beach and does not
  know his way
• Alice is going near there and knows the way
• Bob needs to follow Alice
• Problems
• Alice passed a traffic light while Bob got
  stopped by the red light.
• What should Alice do?
• What does Alice need to know to achieve this?

4
Required Belief about Intentions

• Both should have appropriate intentions
• Both should know about each others intentions
• Both should know that the other knows they have
  such intentions
• Why? How would Bob behave if Bob doesnt know
  whether Alice knows Bob is following her?

5
A Proposal for Joint Intention

• x and y jointly intend to do some collective
  action iff
• it is mutually known between x and y that they
  intend that the collective action occur, and
• it is mutually known that they each intend to do
  their share, and
• the mutual knowledge persists until it is
  mutually known that the activity is over
• Is this OK?

6
Problem of the Proposal

• Too strong.
• It does not allow either one to abandon the joint
  intention.
• It does not allow private beliefs that the
  activity has terminated.

7
Examples for which Alice may abandon her joint
intention ?

• What was changed?

8
Achievement goal

• An agent has an achievement goal relative to q to
  bring about p if the agent does not yet believe
  that p is true now and has p eventually being
  true as a goal.

9
Individual Commitment

• An agent has a persistent goal relative to q to
  achieve p iff
• She believes that p is currently false
• She wants p to be true eventually
• Its is true (and she knows it) that (2) will
  continue to hold until she comes to believe
  either that p is true, or that it will never be
  true, or that q is false

10
Individual Commitment

• Once adopted it can not be dropped freely
• Agent will try again if initial attempts fail
• q is an escape clause, can drop goal when q
  becomes false
• Encodes the network of reasons why agent has
  adopted the commitment

11
Individual Intentions

• A commitment to act in a certain mental state
• Formal definition
• An agent intends relative to some condition to do
  an action just in case she has a persistent goal
  (relative to that condition) of having done the
  action and, having done it, believing throughout
  that she is doing it.

12
Individual Intentions

• Agent commits to p becoming true, without concern
  for who would achieve it and how
• An agent commits to a or b as a way to achieve p
• The agent chooses one of the actions (say a) and
  commits to doing it knowingly.

13
Joint intentions

• Joint intentions are developed in three levels.
• weak achievement goals
• joint persistent goals
• joint intentions

14
Joint commitment

• Weak achievement goal
• Joint persistent goal

15
Weak achievement goal

• An agent has a weak achievement goal relative to
  q and with respect to a team to bring about p if
  either of these conditions holds
• the agent does not yet believe that p is true and
  has p eventually being true as a goal.
• the agent believes that p is true, will never be
  true, or is irrelevant ( that is, q is false),
  but has as a goal that the status of p be
  mutually believed by all the team members.

16
Joint persistent goal

• A team of agents have a joint persistent goal
  relative to q (escape condition) to achieve p
  just in case
• They mutually believe that p is currently false
• They mutually know they all want p to eventually
  be true
• It is true (and mutual knowledge) that until they
  come to mutually believe either that p is true,
  that p will never be true, or that q (the escape
  condition) is false, they will continue to
  mutually believe that they each have p as a weak
  achievement goal relative to q and with respect
  to the team.

17
Theorems

• If a team consists of a single member, then the
  team has a joint persistent goal iff that agent
  has an individual persistent goal.
• If a team has a joint persistent goal to achieve
  p, then each member has p as an individual
  persistent goal.

18
Theorems

• If a team is jointly committed to some goal, then
  under certain conditions, until the team as a
  whole is finished, if one of the members comes to
  believe that the goal is finished but that this
  is not yet mutually known, she will have a
  persistent goal to make the status of the goal
  mutually known.

19
Adopted Proposal

• A team of agents jointly intends, relative to
  some escape condition, to do an action iff the
  members have a joint persistent goal relative to
  that condition of their having done the action
  and, moreover, having done it mutually believing
  throughout that they were doing it.

20
Properties of joint intentions

• Theorem
• If a team jointly intends to do an action, and
  one believes that she is the only agent of that
  action, then she privately intends to do the
  action

21
References

• Cohen, P. R. Levesque, H. J. (1991). Teamwork.
  Nous 25(4), pp. 487-512. Special Issue on
  Cognitive Science and Artifical Intelligence. To
  appear in Handbook of MultiAgent Systems.
• Van Wie, M., (1997). Observation and Cooperation
• http//www.cs.rochester.edu/u/vanwie/paper/pa
  per.html
• Cohen, P. R. Levesque, H. J. (1990). Intention
  is choice with commitment. Artificial
  Intelligent, 42(3)
• Cohen, P. R. Levesque, H. J. (1991).
  Confirmations and joint action. In Proceedings of
  the 12th International Joint Conference on
  Artificial Intelligence.