Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Multi-agent Systems & Coordination Maaike Harbers Delft University of Technology, The Netherlands Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Outline Why do we need coordination in a multi-agent system (MAS)? What is coordination? How can we achieve coordination in a MAS? –Organizational structure –Conventions –Communication How can we use this in GOAL? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkKennistechnologie Why do we need coordination? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Examples of coordination Without coordination, what would happen here? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Examples of coordination And what would happen here? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Examples of coordination Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Coordination needed! Environment A1 Agents A2 A3 A4 Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkKennistechnologie What is coordination? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Definitions of coordination Coordination is......managing dependencies between activities. [Olson et al. 2001]...the complementary temporal sequencing (or synchronicity) of behaviors among team members in the accomplishment of their goal. [Zalesny et al. 1995]...to act in harmonious combination. [dictionary.reference.com] Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Joint activity Studying joint activity as defined by [Clark, 1996] provides a stronger basis for understanding coordination [Klein et al, 2005] A joint activity is an extended set of behaviors that are carried out by an ensemble of people who are coordinating with each other. Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Klein, G., Feltovich, P., Bradshaw, J. M., & Woods, D. D. (2005). Common ground and coordination in joint activity. Organizational Simulation. W. B. Rouse and K. R. Boff. New York City, NY, John Wiley. Aspects of joint activity Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen A. Criteria for joint activity Intention to generate a multi-party product Different from what one person could do working alone Interdependence of the actions of the parties Activities of parties interweave and interact Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen A. Criteria: example Making an assignment together No intention – no assignment or two assignment No interdepencence – each making one half of the assignment without seeing the other half Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Interpredictability –Need to be able to accurately predict what others will do –Not just actions, but the coordination itself Common ground –Pertinent mutual knowledge, beliefs, and assumptions about others’ skills and capabilities –Joint activity is guided by signaling and coordination devices Directability –Capacity for modifying the actions of the other parties as conditions and priorities change –Responsiveness of each participant to the influence of the others B. Requirements for joint activity Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Football team Interpredictability – predict where team members will be on the field and who will be available Common ground – who is keeper, who defends, who attacks Directability – keeper tells others where to stand during a corner B. Requirements: example Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen C. Choreography of joint activity Three phases (functional breakdown) coordinating tasks is coordinating subtasks subtasks have an entry, body and exit phase Signaling transitions within and between phases Coordination devices serve to increase interpredictability examples are organizational structure, convention, communication protocol Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen C. Choreography: example Traffic Three phase actions -entering a road -being on the road -leaving a road Signaling transitions -turn signal Coordination devices -organizational structure, convention, communication protocol -to discuss… Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkKennistechnologie Using coordination devices Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Organizational structure adapted from Bradshaw et al.

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Organizational structure in BW4T Notion of ‘role’ is central Possible roles in BW4T? searcher deliverer manager Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Conventions Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen A group of agents Each agent is able to solve the BW4T task individually Agents do not take into account that there are other agents What happens? Conventions in BW4T Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Do not enter rooms that are occupied If you know about a block that can be delivered, deliver that block If someone intends to deliver a particular block, do not try to deliver that block as well Example of conventions in BW4T Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Conventions in organizational structure Instructions of the manager should always be followed If a searcher finds a block, it must report that to the manager adapted from Bradshaw et al. Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Communication Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen A group of agents Each agent is able to solve the BW4T task individually Agents take into account that there are other agents Agents do not communicate What happens? Communication in BW4T Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Communication Communication can be regulated by conventions Communication often related to roles Communication protocols specify the rules of interaction between two or more communicating agents by restricting the range of allowed follow-up utterances for each agent at any stage during a communicative interaction (dialogue). [Endriss et al. 2004] sequence of related communicative acts Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen BW4T communication protocol M = manager agent W = worker agent Maaike Harbers, M: instructionW: update M: new instruction W: goal accomplished

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen How to use this in GOAL? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen How to Use This in GOAL? (1) functional breakdown (three phases) breakdown of task in subtasks which scheduling of these subtasks? organizational structure which roles can you identify? which (hierarchical/peer-to-peer) relations between the roles? when should agents change role and who decides this? conventions (for communication) when should agents communicate what? which transitions should be signaled? what (if anything) should agents reply to received messages? Use as Design Guidelines for building your multi-agent system

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen How to Use This in GOAL? (2) functional breakdown breakdown of task in subtasks ➸ module for each task scheduling of subtasks ➸ action rules for entering (task) modules organizational structure identification of roles ➸ module for each role relations between roles ➸ action rules for responding to requests changing roles ➸ action rules for entering (role) modules conventions (for communication) when communicate what ➸ action rules for sending messages replies to messages from other agents ➸ action rules for sending messages with received message in mental state condition Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Pattern for Using Task Modules create module for each subtask define entering and exiting conditions use module option “exit=noaction” define action rule for entering module implementation of the three phases action rules of module should implement task agent will exit module if no more actions can be executed; requires corresponding action selection strategy

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Pattern for Using Role Modules create module for each role create entering and exiting policy use module options “exit=nogoals” and “focus=select” define action rule for entering module with goal query to create focus of attention on goal of role Example: if a-goal(delivered(1)) then deliverBlock. module deliverBlock [exit=nogoals,focus=select] {...} action rules of module should aim at achieving goal of module agent will exit module if goal is reached

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Emergency Exit There may be “emergency” circumstances in which to exit a module Task module exiting module using exit-module action before completing the task Role module exiting module by dropping the goal of the module/role using an action rule (because it should not be pursued anymore) exiting module using exit-module action (because goal of role should not be the current focus)

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Study Goals: Coordination Additional exam material: “Klein, G., Feltovich, P., Bradshaw, J. M., & Woods, D. D. (2005). Common ground and coordination in joint activity. (until section 4.4, p 1-16) You should be able to: Explain main notions Apply notions to clarify joint activity in a concrete example Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Example question “As part of my degree requirement we were supposed to do a research project in a group of 5 members. We had to write up a lengthy report and give a presentation within a four week deadline. My colleagues and I decided to split the work accordingly and decided to meet twice a week to give updates of our work and check on the groups progress as a whole making sure our work was in sync. Even though we had decided we would meet twice a week, I often had to do call my colleagues to update them of my progress and find out how they were going on….” To what extent are the criteria for joint activity (intention and interdependence) satisfied in the above example of teamwork? Explain you answer. What is the organizational structure of the team described above, and what kind of role does the writer of this text play? Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Organisation Tutorial this week: –Assignment 4: team agent for BW4T Exam: –Specification of material to study will be posted on blackboard –Example exams are available; however, be aware that there is additional material this year –Possibly there will be several multiple choice questions this year. Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Jomi Fred Hübner, Jaime Simão Sichman, and Olivier Boissier. Developing organised multi-agent systems using the MOISE+ model: Programming issues at the system and agent levels. International Journal of Agent-Oriented Software Engineering, 1(3/4): , 2007.

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Klein, G., Feltovich, P., Bradshaw, J. M., & Woods, D. D. (2005). Common ground and coordination in joint activity. Organizational Simulation. W. B. Rouse and K. R. Boff. New York City, NY, John Wiley. Aspects of Joint Activity Organization & Communication: means for coordination Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Functional Specification adapted from Virginia Dignum Send Call for Papers Form PC Send Call for Participation Paper Submission Review Process Registration Paper Acceptance Conference on-site registration Conference Sessions M start end Workshops N Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Notion of ‘role’ is central organization goals agents agent roles determine performed by Organizational perspective society agent roles agent goals determine performed within Agent perspective adapted from Virginia Dignum Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Top down vs bottom up Top-down: organization organizational structure functional specification global norms/policies/regulations Bottom-up: emergent behavior emergent organization sustain and repair common ground local norms/policies/regulations Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Example: Acknowledgement Policy Set A Robot is obligated to acknowledge to the Requestor when the Robot Accepts an Action Acknowledgement adapted from Bradshaw et al. Maaike Harbers,

Koen Hindriks, Birna van Riemsdijk Multi-agent systemen Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Multi-agent system Environment A1 Agents A2 A3 A4 Intersecting spheres of influence of multiple agents acting in an environment Intersecting spheres: Action perspective: may interfere, change same parts of environment Perception perspective: agents may have different views on environment Maaike Harbers,