Feb 24, 2003Feb 24, 2003

Agent-based Agent-based Proactive TeamworkProactive Teamwork

John YenJohn Yen

University Professor of ISTUniversity Professor of ISTSchool of Information Sciences and TechnologySchool of Information Sciences and Technology

The Pennsylvania State UniversityThe Pennsylvania State University

Feb 24, 2003Feb 24, 2003

Motivation Motivation

Psychological Studies about Effective Psychological Studies about Effective Human Teamwork Indicated thatHuman Teamwork Indicated that

Team members can Team members can anticipate needsanticipate needs of of team matesteam mates

Team members can offer relevant Team members can offer relevant information information proactivelyproactively..

These teamwork behaviors are based on These teamwork behaviors are based on an overlapping an overlapping shared mental modelshared mental model. .

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A Response to the A Response to the ChallengesChallenges

Empower agents with ``Empower agents with ``shared shared mental modelsmental models" to enable them to " to enable them to betterbetter Anticipate information needs of Anticipate information needs of

teammates in a dynamic environmentteammates in a dynamic environment Offer relevant information proactively to Offer relevant information proactively to

soldiers soldiers

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Shared Mental ModelShared Mental Model Shared OntologyShared Ontology Shared GoalsShared Goals Shared Team StructureShared Team Structure Shared Team Collaboration ProcessShared Team Collaboration Process Shared Belief about the TeamShared Belief about the Team Shared Belief about the World Shared Belief about the World

Shared Hypotheses about the EnemyShared Hypotheses about the Enemy

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Major Features of CASTMajor Features of CAST

Use a high-level language to describe Use a high-level language to describe teamwork knowledgeteamwork knowledge

Capture “shared mental model” about Capture “shared mental model” about team structure and processteam structure and process

InfersInfers information needs (from SMM) information needs (from SMM) inducesinduces proactive information exchanges proactive information exchanges

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Anticipating Information Anticipating Information Needs of TeammatesNeeds of Teammates

Team PlanResponsibilities

of Tasks

Preconditions ofTasks

Information Needs

DynamicTask

Allocation

Who

needs what

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Dynamic Task AllocationDynamic Task Allocation

Team Plan

Constraints for TaskAllocation

Roles of Agents in the Team

My Belief aboutThe World

My Belief aboutTeammates

DynamicTask

Allocation

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Proactive Information Proactive Information DeliveryDelivery

My Belief aboutTeammates

Information Needs

InformationMatch ?

CommunicationStrategy

Does he/sheknow ?

How toinform him/her?

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CAST Agent ArchitectureCAST Agent Architecture

TeamKnowledge (MALLET)

Responsibilities(Petri Nets)

Belief

DomainKnowledge

ResponsibilitySelection

IdentifyInfo Needs

InformationNeeds

InformationBeliefUpdate

Act onInfo Needs

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Shared Mental Model in Shared Mental Model in CASTCAST

Prolog knowledge base: beliefProlog knowledge base: belief MALLET: High-level language for MALLET: High-level language for

representing team knowledgerepresenting team knowledge Petri Nets: An agent’s internal Petri Nets: An agent’s internal

representation of the dynamic representation of the dynamic teamwork processesteamwork processes and related and related information requirementsinformation requirements

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Relationships between SMM Relationships between SMM ComponentsComponents

MALLETKnowledge Base

PrologKnowledge Base

(belief)

MALLETCompiler

Petri Net(team process)

query

reply

CASTKernel

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(team-plan T1 () (team-plan T1 () (process (par (kill-wumpuses) (collect-(process (par (kill-wumpuses) (collect-

gold))))gold))))

(team-plan kill-wumpuses ()(team-plan kill-wumpuses () (agent-bind ?s (play-role ?s scout))(agent-bind ?s (play-role ?s scout)) (agent-bind ?f (play-role ?f fighter)(closest (agent-bind ?f (play-role ?f fighter)(closest

?f wumpus))?f wumpus)) (process (while ((wumpus ?x) (not (dead ?(process (while ((wumpus ?x) (not (dead ?

x))))x)))) (seq (do ?s (find-wumpus ?x)) (seq (do ?s (find-wumpus ?x)) (do ?f (move-to-wumpus ?x)) (do ?f (move-to-wumpus ?x)) (do ?f (shoot-wumpus ?x)))))(do ?f (shoot-wumpus ?x)))))(team-plan find-gold ()(team-plan find-gold () (agent-bind ?c (play-role ?c carrier))(agent-bind ?c (play-role ?c carrier)) (process (while (true) (if (see ?any-agent (process (while (true) (if (see ?any-agent

glitter) glitter) (do ?c (carrier-pickup gold))))(do ?c (carrier-pickup gold))))

start find shootmove

wumpus exists

glitter

done

no wumpuses left

pickup

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Domain Simulator

Team Process ExecutionTeam Process Specification

CAST Software CAST Software ArchitectureArchitecture

MALLET

Team Structure

Process Net

Knowledge BaseKernel

Agent Selection

Goal Selection

Domain World

Communication

Fact Base & Domain Policy

Monitor

Monitor

Inference Engine

Parser

Domain Adapter

Inference Engine

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CAST Development CAST Development Environ.Environ.

Circles are places and hold tokens denoting current execution state. Red indicates the presence of a token. Rectangles are transitions and are tested and executed when preceding places have tokens.

Circles are places and hold tokens denoting current execution state. Red indicates the presence of a token. Rectangles are transitions and are tested and executed when preceding places have tokens.

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Theoretical Foundations of Theoretical Foundations of CASTCAST

What are the principles that derive What are the principles that derive “information needs”?“information needs”?

What is the semantics of proactive What is the semantics of proactive information delivery?information delivery?

How does an agent choose among How does an agent choose among different proactive communication different proactive communication strategies?strategies?

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Agent TheoriesAgent Theories

Joint Intention theory (Cohen & Joint Intention theory (Cohen & Levesque)Levesque)

SharedPlan Theory (Grosz & Kraus)SharedPlan Theory (Grosz & Kraus)

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Two Types of Information Two Types of Information needsneeds

Action-performing information needsAction-performing information needs enables an agent to perform certain enables an agent to perform certain

(complex) actions, which contributes to (complex) actions, which contributes to an agent's individual commitments to an agent's individual commitments to the whole team.the whole team.

Goal-protection information needsGoal-protection information needs allows an agent to protect a goal from allows an agent to protect a goal from

potential threats that may result in a potential threats that may result in a conflict with the goal.conflict with the goal.

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Semantics of Assert Semantics of Assert Performative (Cohen & Performative (Cohen &

Levesque)Levesque) The speaker attempts to establish a The speaker attempts to establish a

joint belief with the receiver thatjoint belief with the receiver that The speaker believes the informationThe speaker believes the information

Whether the receives accept the Whether the receives accept the belief depends on the reply (accept belief depends on the reply (accept or reject)or reject)

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Semantics of ProAssertSemantics of ProAssert

The speaker attempts to establish a The speaker attempts to establish a joint belief with the receiver thatjoint belief with the receiver that The speaker believes the informationThe speaker believes the information The speaker believes that the receiver The speaker believes that the receiver

needsneeds the information the information

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Semantics of ProAssertSemantics of ProAssert

An attempt for the speaker (s) to establish a An attempt for the speaker (s) to establish a joint belief that joint belief that

1.1. S believes in the information (p)S believes in the information (p)

2.2. S believes that the receiver (a) needs the information.S believes that the receiver (a) needs the information.

0 0 0

Pr ( , , , , ') ( , , ) ( , ( , , '), )( , (Pr ), ( ') ( , , ),

'' ( '' ') ({ , }, , ''), , , '),( '' ') . ( , ( , ( , ( , ,b b

oAssert s a p t t Bel s p t Bel s Need a p t tAttempt s e oAssert t t t t Bel a p tt t t t MB s a P t t t whereP t t t t IntTh s Bel a Bel s p Need a p t

1 1 1

'), ), ), , , ( , ( , , ), )),

( ') ( , ( , , ), )

b

b a a

t tt t Bel s t Bel a p t tt t t t Bel s Need a p t t

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Responses to ProAssertResponses to ProAssert

Three possible responses to ProAssert:Three possible responses to ProAssert: Accept: The receiver believes the Accept: The receiver believes the

informationinformation Reject1: The receiver refuses the Reject1: The receiver refuses the

information because the information is information because the information is contradictory to its beliefs.contradictory to its beliefs.

Reject2: The receiver refuses the Reject2: The receiver refuses the information because it believes information because it believes it does it does not need the informationnot need the information

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Inferring Proactive Assert from Inferring Proactive Assert from Information NeedsInformation Needs

Derived from the Assist Axiom in Derived from the Assist Axiom in SharedPlan theory:SharedPlan theory:

0 0 0

( , ( , , '), ) ( , , )

(/ ( ) ( ,Pr ( , , , , '), ))

( . . ( ,Pr ( , , , , '), , , _ ( , )))t t t

Bel A Need B I t t Bel A I t

t t t Bel A oAsserted A B I t t t

t Pot Int To A oAssert A B I t t t t C needs B I

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Choosing Communication Choosing Communication PoliciesPolicies

How to inform teammates? Proactive or How to inform teammates? Proactive or wait for them to ask?wait for them to ask?

Factors that affect the policiesFactors that affect the policies Cost of communicationsCost of communications Certainty level about teammate’s needsCertainty level about teammate’s needs Consequence of communicationsConsequence of communications Criticality of the information to teammatesCriticality of the information to teammates Load level of teammatesLoad level of teammates

These factors depend on situations agents These factors depend on situations agents are inare in

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Decision-theoretic Decision-theoretic Approach to Approach to

CommunicationCommunication Use decision theory for choosing Use decision theory for choosing

communication strategiescommunication strategies Assign utility to plansAssign utility to plans Assess the value of information from Assess the value of information from

the utility of plansthe utility of plans Specify probabilities in JARESpecify probabilities in JARE

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ExperimentExperiment

Goal: Evaluate Two Proactive Goal: Evaluate Two Proactive Communication StrategiesCommunication Strategies

StrategyStrategy Action-performing Action-performing Information NeedsInformation Needs

Goal-protectionGoal-protection

Information NeedsInformation Needs

S1S1 Always ProInformAlways ProInform Always ProInformAlways ProInform

S2S2 Decision-theoretic Decision-theoretic ProInformProInform

Decision-theoreticDecision-theoretic

ProInformProInform

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MALLET ExampleMALLET Example

(action attack-enemy ()(action attack-enemy ()(pre-cond (is-enemy_homebase ?h1)(pre-cond (is-enemy_homebase ?h1)

(at ?h1 ?x ?y) )(at ?h1 ?x ?y) )(process(process

(par(par(do scoutteam seeking)(do scoutteam seeking)(do fighterteam attacking-wumpus)(do fighterteam attacking-wumpus)(do boomerteam attacking-base ?x ?y)(do boomerteam attacking-base ?x ?y)

) ) )) ) )

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Petri Net – Process Petri Net – Process RepresentationRepresentation

Parsed from Parsed from MALLETMALLET

Hierarchical Hierarchical structurestructure

Extended with Extended with predicatepredicate

Support basic Support basic processes such as processes such as sequential, parallel, sequential, parallel, and conditional and conditional

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Domain OverviewDomain Overview

Two teams, attack team (blue) and Two teams, attack team (blue) and defense team (red)defense team (red)

The mission of the blue team to is to The mission of the blue team to is to destroy enemy base by flowing certain destroy enemy base by flowing certain waypointswaypoints Communication riskCommunication risk Different observabilityDifferent observability

The red team will patrol around the The red team will patrol around the waypoints and home basewaypoints and home base

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Domain Simulation InterfaceDomain Simulation Interface

Blue teamBlue team Red teamRed team WaypointWaypoint Enemy BaseEnemy Base

Agent MonitorAgent Monitor World MonitorWorld Monitor

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Experiment ResultExperiment Result

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6

DB_PROTELL

PROTELL

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ApplicationsApplications

Training for AWACS-like synthetic Training for AWACS-like synthetic task (AFOSR MURI)task (AFOSR MURI)

Support Horizontal Fusion STO (Army Support Horizontal Fusion STO (Army Research Lab)Research Lab)

Negotiation among Agent Teams for Negotiation among Agent Teams for Design (NSF)Design (NSF)

Supporting Analyst Teams (Lockheed Supporting Analyst Teams (Lockheed Martin)Martin)

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ConclusionConclusion

A A computational shared mental modelcomputational shared mental model is critical is critical for developing agents that support for developing agents that support proactiveproactive teamwork.teamwork.

CAST enables proactive information delivery by CAST enables proactive information delivery by anticipatinganticipating needs of teammates. needs of teammates.

MALLET facilitates the reuse of teamwork MALLET facilitates the reuse of teamwork knowledge knowledge

CAST achieves CAST achieves efficiencyefficiency using shared team plans using shared team plans and shared policyand shared policy

CAST achieves CAST achieves adaptabilityadaptability by dynamic by dynamic assignment of agent responsibilityassignment of agent responsibility