Modeling Teamwork in the CAST Multi-Agent System Thomas R. Ioerger Department of Computer Science Texas A&M University

The Nature of Teamwork Team Psychology Research: Salas, Cannon-Bowers, Serfaty, Ilgen, Hollenbeck, Koslowski, etc. –2 or more individuals working together... –members often distinct roles –types of control: centralized (hierarchical) vs. distributed (consensus-oriented) –process measures vs. outcome measures –communication, adaptiveness –shared mental models

Computational Models of Teamwork Commitment to shared goals –Joint Intentions (Cohen & Levesque; Tambe) –Cooperation, non-interference –Backup roles, helping behavior Mutual awareness –goals of teammates; achievement status –information needs Coordination, synchronization Distributed decision making –consensus formation (voting), conflict resolution

CAST: Collaborative Agent Architecture for Simulating Teamwork developed at Texas A&M; part of MURI grant from DoD/AFOSR, plus support from ARL multi-agent system implemented in Java components: –MALLET: a high-level language for describing team structure and processes –JARE: logical inference, knowledge base –Petri Net representation of team plan –special algorithms for: belief reasoning, situation assessment, information exchange, etc.

CAST Architecture MALLET knowledge base (definition of roles, tasks, etc.) JARE knowledge base (domain rules) Agent expand team tasks into Petri nets keep track of who is doing each step make queries to evaluate conditions, assert/retract information models of other agents’ beliefs agent teammates human teammates simulation messages events, actions state data

MALLET (role sam scout) (role bill S2) (role joe FSO) (responsibility S2 monitor-threats) (capability UAV-operator maneuver-UAV) (team-plan indirect-fire (?target) (select-role (scout ?s) (in-visibility-range ?s ?target)) (process (do S3 (verify-no-friendly-units-in-area ?target)) (while (not (destroyed ?target)) (do FSO (enter-CFF ?target)) (do ?s (perform-BDA ?target)) (if (not (hit ?target)) (do ?s (report-accuracy-of-aim FSO)) (do FSO (adjust-coordinates ?target)))))) evaluated by queries to JARE knowledge base descriptions of team structure descriptions of team process

JARE Knowledge Base First-order Horn-clauses (rules with variables) Similar to PROLOG Make inferences by back-chaining consequent antecedents ((threat ?a ?b)(enemy ?a)(friendly ?b) (in-contact ?a ?b)(larger ?a ?b) (intent ?a aggression)) >(query (threat ?x TF-122)) solution 1: ?x = Reg-52 solution 2: ?x = Reg-54

Proactive Information Exchange Information sharing is a key to efficient teamwork Want to capture information flow in team, including proactive distribution of information Agent A should send message I to Agent B iff: –A believes I is true –A believes B does not already believe I (non-redundant) –I is relevant to one of B’s goals, i.e. pre-condition of current goal that B is responsible for in plan DIARG Algorithm (built into CAST): 1. check for transitions which other agents are responsible for that can fire (pre-conds satisfied) 2. infer whether other agent might not believe pre-conds are true (currently, beliefs based on post-conditions of executed steps, i.e. tokens in output places) 3. send proactive message with information

Belief Reasoning Modeling teammates’ beliefs - an important component of a shared mental model Knowledge of pre-conds and effects of actions Mutual observability - common events in env. –e.g. messages on radio net; symbols shared on radar Interaction with other justifications of beliefs: –inferences, assumptions, persistence –Prioritized logic program impacts team interactions and communications (bel S2 (attacking reg-54 TF-122)) (bel S2 (location Reg-60 unknown)) (bel S6 (cutoff supply-route TF-122)) S3-agent’s database

Situation Awareness Central part of Command-and-Control –information gathering, group decision-making, Drives communication within teams in tactical environments Our approach: based on RPD –Recognition-Primed Decision-Making –Finite set of anticipated situations: e.g. flank attack, deception, bypass, pincer –Look for features associated with each situation –Trigger when sufficient features found

Implementation of SA in CAST Generic plan for RPD in MALLET Domain-specific situations and features encoded in JARE predicates Plan executes loop: While no situation has sufficient features detected: For each feature F whose value is unknown but potentially relevant to situation, try to find out about status of F Domain-specific find-out procedures encoded as sub-tasks: ask scouts, ask radar operator, ask S2, use UAV, check JSTARs, take probing actions... info. management: what questions to ask when? current work: extend to multi-agent team plan

Applications of CAST Battalion Tactical Operations Centers –model of staff operations (agents=S2, S3, FSO...) –hooked-up to OTB (OneSAF Testbed Baseline) –focus on modeling information flow –interact with human brigade staff trainees via report/request forms AWACS weapons directors –model coordination, load-balancing –hooked-up to DDD simulation (Aptima) –studying effects of workload on helping behavior