Collaborative Context Based Reasoning CCxBR

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Collaborative Context Based Reasoning (CCxBR)

• Gil Barrett
• Avelino Gonzalez
• Intelligent Systems Laboratory
• University of Central Florida

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• Outline
• Context Based Reasoning (CxBR) Overview
• Belief Desire Intentions (BDI)
• Joint Intentions Theory (JIT)
• Context Based Reasoning (CxBR) Formalisms
• Collaborative Context Based Reasoning (CCxBR)
• Team Models

CxBR BDI JIT
CCxBR Team Models
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• Purpose
• The motivation for the research described here
  is to formally describe teamwork for a contextual
  reasoning paradigm, specifically teamwork is
  defined for Context Based Reasoning based on
  Joint Intentions Theory.

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• SimpleCxBRModel

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• SimpleCxBRModel

A CxBR agent has an associated knowledge base to
store believed facts about the environment. This
knowledge base is implementation dependent and
not strictly specified by the CxBR paradigm.
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• SimpleCxBRModel

A CxBR Mission includes the agents goal.

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• SimpleCxBRModel

CxBR Missions have an associated set of Contexts.

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• SimpleCxBRModel

CxBR Contexts each include context specific
sub-goals.

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• SimpleCxBRModel

A Context is considered Active when transition
requirements and possibly transition criteria are
met.

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• SimpleCxBRModel

The Active Context determines a CxBR agents
high-level behaviors.

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• Belief Desire Intention
• Perhaps the most common paradigm for modeling
  intelligent agents is the belief-desire-intention
  model 1. Georgeff loosely defines BDI as
  follows
• Beliefs - represent knowledge the agent possesses
  of the world.
• Desires - correspond to goals of the agent.
• Intentions - are plans to which an agent is
  committed.
• These definitions are critical in defining terms
  related to collaboration and teamwork.

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• Joint Intention Theory
• Joint Intention Theory (JIT)2 is a set of
  definitions and corresponding theorems which
  define teamwork.
• JIT itself does not provide an implementation of
  these theorems, but has been implemented by many
  researches since 1991.
• However, very little has been done to incorporate
  JIT with contextual reasoning paradigms.

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• Joint Intentions Theory
• Definition 1 An agent has a persistent goal
  relative to q to achieve p iff
• The agent believes that p is currently false
• The agent wants p to be true eventually
• It is true (and the agent knows it) that (2)
  will continue to hold until the agent comes to
  believe either that p is true, or that it will
  never be true, or that q is false.

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• Joint Intentions Theory
• Definition 2 An agent intends relative to some
  condition to do an action just in case the agent
  has a persistent goal (relative to that
  condition) of having done the action and,
  moreover, having done it, believing throughout
  that the agent is doing it.

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• Joint Intentions Theory
• Definition 3 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 has a normal achievement goal to bring
  about p, that is, 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 (thus q is false), but has
  a goal that the status of p be mutually believed
  by all the team members.

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• Joint Intentions Theory
• Definition 4 A team of agents have a joint
  persistent goal relative to q 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 mutually known) that until they
  come to mutually believe either that p is true,
  that p will never be true, or that q 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.

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• Joint Intentions Theory
• Definition 5 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.

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• CxBR Formalisms
• Corollary 1 High level desires and goals are
  captured in CxBR Missions. Lower relative
  sub-goals and desires are captured in the
  Missions associated Contexts and Sub-Contexts.
• Corollary 2 Given fact q is a transition
  requirement of Context c, if c is the Active
  Context then q is believed true.
• Corollary 3 Given Context c is part of the
  context set associated with Mission m and m
  contains goal g, if c is the Active Context for
  an agent with Mission m, then the agent has
  Mission goal g and any goals (Mission sub-goals)
  of c.
• Corollary 4 The sequence of Active Contexts for
  a CxBR agent is the agents plan.

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• Collaborative CxBR Formalisms
• Theorem 1 A CxBR agent has a persistent goal
  (individual commitment) relative to q to achieve
  p iff The Active Context c has transition
  requirement q and goal p or if the Active Context
  c has transition requirement q and the Mission m
  has goal p.
• This is justified from the JIT Definition 1 of a
  persistent goal and CxBR corollaries 2 and 3.

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• Collaborative CxBR Formalisms
• Theorem 2 A CxBR agent intends relative to some
  condition, consisting at a minimum of some
  transition criterion, to do an action determined
  by the agents Active Context for the sake of a
  persistent goal.
• This theorem is adapted from the JIT Definition 2
  for intentions and the fact that actions in CxBR
  are determined by the agents Active Context.

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• Collaborative CxBR Formalisms
• Theorem 3 A CxBR agent has a weak achievement
  goal relative to q and with respect to a team to
  bring about p if The agents Active Context is
  part of Mission ms related Contexts intended to
  accomplish p, or the agent has a goal that the
  status of p be mutually believed by all other
  teammates, regardless of the current state of p
  (true, false, or irrelevant).
• This is justified by the JIT definition for weak
  achievement goal and the fact that the sequence
  of Contexts forms a plan that allows the
  accomplishment of the Mission goal.

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• Collaborative CxBR Formalisms
• Theorem 4 A team of CxBR agents has a joint
  persistent goal relative to q to achieve p if
  each agent shares the same team Mission with goal
  p.
• This is justified by the JIT Definition 4 for
  joint persistent goal and Corollary 1.

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• Collaborative CxBR Formalisms
• Theorem 5 A team of CxBR agents jointly intends
  to do some action iff they share the same team
  Mission and believe they are accomplishing their
  Mission by following a plan of Mission related
  Contexts.

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• Collaborative CxBR Formalisms
• Theorem 6 Theorem 4 and theorem 5 could both be
  extended to include Context rather than Mission
  as a matter of scale.
• This is justified since Mission is essentially a
  special form of Context. When considering a
  Context hierarchy including multiple Missions,
  the Missions themselves become the Context-set of
  some higher Mission.

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• Collaborative CxBR Formalisms Summarized
• Commitment to a mutual goal can be ascertained
  between CxBR agents by communicating/identifying
  the agents Mission and Active Context.
• This requires a minimum familiarity of each
  agents Contexts by all team-members. Given
  this, agents can be aware of team-members
  intentions and beliefs based on the team-members
  Active Context and the perceiving agents
  understanding of those Contexts.

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Diagonal-Combination-play-Context
Box-Combination-play-Context
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SimplifiedMidfielderModel
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SimpleModel
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Modeling Team Hierarchies
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Modeling Team Hierarchies
Abstract Class from which teams and team members
both inherit.
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Used to model single-entities, such as
team-members.
Modeling Team Hierarchies
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Modeling Team Hierarchies
Used to model group-entities, such as teams.
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Team Model
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Embedded Contexts
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Co-Contexts
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Collaborative Context Based Reasoning
(CCxBR)??? Questions ???

• Gil Barrett
• Avelino Gonzalez
• Intelligent Systems Laboratory
• University of Central Florida

CxBR BDI JIT
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• References
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• 2 Cohen, P. R., Levesque, H. J., 1991
  Teamwork. Nous, 35 1991
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  Journal of Artificial Intelligence Research 7,
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  Artificial Intelligence Research Society 2004.
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