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Transcript of Koen Hindriks, Birna van RiemsdijkMulti-agent systemen Multi-agent Systems & Coordination Maaike...
Koen Hindriks, Birna van Riemsdijk Multi-agent systemen
Multi-agent Systems & Coordination
Maaike HarbersDelft University of Technology, The Netherlands
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Kennistechnologie 2009-2010
Why do we need coordination?
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Examples of coordination
• Without coordination, what would happen here?
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Examples of coordination
http://www.wired.com/gadgetlab/2010/06/dance-dance-revolution-20-robots-think-they-can-dance/
• And what would
happen here?
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Examples of coordination
http://cacm.acm.org/news/98755-how-football-playing-robots-have-the-future-of-ai-at-their-feet/fulltext
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Coordination needed!
Environment
A1Agents A2
A3
A4
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Kennistechnologie 2009-2010
What is coordination?
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 acorner
B. Requirements: example
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Kennistechnologie 2009-2010
Using coordination devices
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Organizational structure
adapted from Bradshaw et al.
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Conventions
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
Communication
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
BW4T communication protocol
• M = manager agent
• W = worker agent
Maaike Harbers,
0 1 2 3
M: instruction W: update
M: new instruction
W: goal accomplished
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-agent systemen
How to use this in GOAL?
Maaike Harbers,
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemUse as Design Guidelines for building your multi-agent system
Koen Hindriks, Birna van Riemsdijk Multi-agent systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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 email 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 systemenKoen Hindriks, Birna van Riemsdijk Multi-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,