Multi-agent system

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Simple reflex agent
Learning agent

A multi-agent system (MAS or "self-organized system") is a computerized system composed of multiple interacting intelligent agents.[1] Multi-agent systems can solve problems that are difficult or impossible for an individual agent or a monolithic system to solve.[2] Intelligence may include methodic, functional, procedural approaches, algorithmic search or reinforcement learning.[3][4]

Despite considerable overlap, a multi-agent system is not always the same as an agent-based model (ABM). The goal of an ABM is to search for explanatory insight into the collective behavior of agents (which don't necessarily need to be "intelligent") obeying simple rules, typically in natural systems, rather than in solving specific practical or engineering problems. The terminology of ABM tends to be used more often in the science, and MAS in engineering and technology.[5] Applications where multi-agent systems research may deliver an appropriate approach include online trading,[6] disaster response,[7][8] target surveillance [9] and social structure modelling.[10]


Multi-agent systems consist of agents and their environment. Typically multi-agent systems research refers to software agents. However, the agents in a multi-agent system could equally well be robots, humans or human teams. A multi-agent system may contain combined human-agent teams.

Agents can be divided into types spanning simple to complex. Categories include:

  • Passive agents[11] or "agent without goals" (such as obstacle, apple or key in any simple simulation)
  • Active agents[11] with simple goals (like birds in flocking, or wolf–sheep in prey-predator model)
  • Cognitive agents (complex calculations)

Agent environments can be divided into:

  • Virtual
  • Discrete
  • Continuous

Agent environments can also be organized according to properties such as accessibility (whether it is possible to gather complete information about the environment), determinism (whether an action causes a definite effect), dynamics (how many entities influence the environment in the moment), discreteness (whether the number of possible actions in the environment is finite), episodicity (whether agent actions in certain time periods influence other periods),[12] and dimensionality (whether spatial characteristics are important factors of the environment and the agent considers space in its decision making).[13] Agent actions are typically mediated via an appropriate middleware. This middleware offers a first-class design abstraction for multi-agent systems, providing means to govern resource access and agent coordination.[14]


The agents in a multi-agent system have several important characteristics:[15]

  • Autonomy: agents at least partially independent, self-aware, autonomous
  • Local views: no agent has a full global view, or the system is too complex for an agent to exploit such knowledge
  • Decentralization: no agent is designated as controlling (or the system is effectively reduced to a monolithic system)[16]

Self-organisation and self-direction[edit]

Multi-agent systems can manifest self-organisation as well as self-direction and other control paradigms and related complex behaviors even when the individual strategies of all their agents are simple.[citation needed] When agents can share knowledge using any agreed language, within the constraints of the system's communication protocol, the approach may lead to a common improvement. Example languages are Knowledge Query Manipulation Language (KQML) or Agent Communication Language (ACL).

System paradigms[edit]

Many MAS are implemented in computer simulations, stepping the system through discrete "time steps". The MAS components communicate typically using a weighted request matrix, e.g.

 Speed-VERY_IMPORTANT: min=45 mph, 
 Path length-MEDIUM_IMPORTANCE: max=60 expectedMax=40, 
 Contract Priority-REGULAR 

and a weighted response matrix, e.g.

 Speed-min:50 but only if weather sunny, 
 Path length:25 for sunny / 46 for rainy
 Contract Priority-REGULAR
 note – ambulance will override this priority and you'll have to wait

A challenge-response-contract scheme is common in MAS systems, where

  • First a "Who can?" question is distributed.
  • Only the relevant components respond: "I can, at this price".
  • Finally, a contract is set up, usually in several short communication steps between sides,

also considering other components, evolving "contracts" and the restriction sets of the component algorithms.

Another paradigm commonly used with MAS is the "pheromone", where components leave information for other nearby components. These pheromones may evaporate/concentrate with time, that is their values may decrease (or increase).


MAS tend to find the best solution for their problems without intervention. There is high similarity here to physical phenomena, such as energy minimizing, where physical objects tend to reach the lowest energy possible within the physically constrained world. For example: many of the cars entering a metropolis in the morning will be available for leaving that same metropolis in the evening.

The systems also tend to prevent propagation of faults, self-recover and be fault tolerant, mainly due to the redundancy of components.


The study of multi-agent systems is "concerned with the development and analysis of sophisticated AI problem-solving and control architectures for both single-agent and multiple-agent systems."[17] Research topics include:


Frameworks have emerged that implement common standards (such as the FIPA and OMG MASIF[22] standards). These frameworks e.g. JADE, save time and aid in the standardization of MAS development.[23]

Currently though, no standard is actively maintained from FIPA or OMG. Efforts for further development of software agents in industrial context are carried out in IEEE IES technical committee on Industrial Agents.[24]


MAS have not only been applied in academic research, but also in industry.[25] MAS are applied in the real world to graphical applications such as computer games. Agent systems have been used in films.[26] It is widely advocated for use in networking and mobile technologies, to achieve automatic and dynamic load balancing, high scalability and self-healing networks. They are being used for coordinated defence systems.

Other applications[27] include transportation,[28] logistics,[29] graphics, manufacturing, power system,[30] smartgrids[31] and GIS.

Also, Multi-agent Systems Artificial Intelligence (MAAI) are used for simulating societies, the purpose thereof being helpful in the fields of climate, energy, epidemiology, conflict management, child abuse, ....[32] Some organisations working on using multi-agent system models include Center for Modelling Social Systems, Centre for Research in Social Simulation, Centre for Policy Modelling, Society for Modelling and Simulation International.[32]

Vehicular traffic with controlled autonomous vehicles can be modelling as a multi-agent system involving crowd dynamics.[33] Hallerbach et al. discussed the application of agent-based approaches for the development and validation of automated driving systems via a digital twin of the vehicle-under-test and microscopic traffic simulation based on independent agents.[34] Waymo has created a multi-agent simulation environment Carcraft to test algorithms for self-driving cars.[35][36] It simulates traffic interactions between human drivers, pedestrians and automated vehicles. People's behavior is imitated by artificial agents based on data of real human behavior.

See also[edit]


  1. ^ Hu, J.; Bhowmick, P.; Jang, I.; Arvin, F.; Lanzon, A., "A Decentralized Cluster Formation Containment Framework for Multirobot Systems" IEEE Transactions on Robotics, 2021.
  2. ^ Hu, J.; Turgut, A.; Lennox, B.; Arvin, F., "Robust Formation Coordination of Robot Swarms with Nonlinear Dynamics and Unknown Disturbances: Design and Experiments" IEEE Transactions on Circuits and Systems II: Express Briefs, 2021.
  3. ^ Hu, J.; Bhowmick, P.; Lanzon, A., "Group Coordinated Control of Networked Mobile Robots with Applications to Object Transportation" IEEE Transactions on Vehicular Technology, 2021.
  4. ^ Wiering, M. A. (2000). "Multi-agent reinforcement learning for traffic light control". Machine Learning: Proceedings of the Seventeenth International Conference (Icml'2000): 1151–1158. hdl:1874/20827.
  5. ^ Niazi, Muaz; Hussain, Amir (2011). "Agent-based Computing from Multi-agent Systems to Agent-Based Models: A Visual Survey" (PDF). Scientometrics. 89 (2): 479–499. arXiv:1708.05872. doi:10.1007/s11192-011-0468-9. S2CID 17934527.
  6. ^ Rogers, Alex; David, E.; Schiff, J.; Jennings, N.R. (2007). "The Effects of Proxy Bidding and Minimum Bid Increments within eBay Auctions". ACM Transactions on the Web. 1 (2): 9–es. CiteSeerX doi:10.1145/1255438.1255441. S2CID 207163424. Archived from the original on 2010-04-02. Retrieved 2008-03-18.
  7. ^ Schurr, Nathan; Marecki, Janusz; Tambe, Milind; Scerri, Paul; Kasinadhuni, Nikhil; Lewis, J.P. (2005). "The Future of Disaster Response: Humans Working with Multiagent Teams using DEFACTO" (PDF). Archived from the original (PDF) on 2013-06-03. Retrieved 2012-04-28. {{cite journal}}: Cite journal requires |journal= (help)
  8. ^ Genc, Zulkuf; et al. (2013). "Agent-based information infrastructure for disaster management" (PDF). Intelligent Systems for Crisis Management. Lecture Notes in Geoinformation and Cartography: 349–355. doi:10.1007/978-3-642-33218-0_26. ISBN 978-3-642-33217-3.
  9. ^ Hu, Junyan; Bhowmick, Parijat; Lanzon, Alexander (2020). "Distributed Adaptive Time-Varying Group Formation Tracking for Multiagent Systems With Multiple Leaders on Directed Graphs". IEEE Transactions on Control of Network Systems. 7: 140–150. doi:10.1109/TCNS.2019.2913619. S2CID 149609966.
  10. ^ Sun, Ron; Naveh, Isaac (30 June 2004). "Simulating Organizational Decision-Making Using a Cognitively Realistic Agent Model". Journal of Artificial Societies and Social Simulation.
  11. ^ a b Kubera, Yoann; Mathieu, Philippe; Picault, Sébastien (2010), "Everything can be Agent!" (PDF), Proceedings of the Ninth International Joint Conference on Autonomous Agents and Multi-Agent Systems (AAMAS'2010): 1547–1548
  12. ^ Russell, Stuart J.; Norvig, Peter (2003), Artificial Intelligence: A Modern Approach (2nd ed.), Upper Saddle River, New Jersey: Prentice Hall, ISBN 0-13-790395-2
  13. ^ Salamon, Tomas (2011). Design of Agent-Based Models. Repin: Bruckner Publishing. p. 22. ISBN 978-80-904661-1-1.
  14. ^ Weyns, Danny; Omicini, Amdrea; Odell, James (2007). "Environment as a first-class abstraction in multiagent systems". Autonomous Agents and Multi-Agent Systems. 14 (1): 5–30. CiteSeerX doi:10.1007/s10458-006-0012-0. S2CID 13347050.
  15. ^ Wooldridge, Michael (2002). An Introduction to MultiAgent Systems. John Wiley & Sons. p. 366. ISBN 978-0-471-49691-5.
  16. ^ Panait, Liviu; Luke, Sean (2005). "Cooperative Multi-Agent Learning: The State of the Art" (PDF). Autonomous Agents and Multi-Agent Systems. 11 (3): 387–434. CiteSeerX doi:10.1007/s10458-005-2631-2. S2CID 19706.
  17. ^ "The Multi-Agent Systems Lab". University of Massachusetts Amherst. Retrieved Oct 16, 2009.
  18. ^ Albrecht, Stefano; Stone, Peter (2017), "Multiagent Learning: Foundations and Recent Trends. Tutorial", IJCAI-17 conference (PDF)
  19. ^ Cucker, Felipe; Steve Smale (2007). "The Mathematics of Emergence" (PDF). Japanese Journal of Mathematics. 2: 197–227. doi:10.1007/s11537-007-0647-x. S2CID 2637067. Retrieved 2008-06-09.
  20. ^ Shen, Jackie (Jianhong) (2008). "Cucker–Smale Flocking under Hierarchical Leadership". SIAM J. Appl. Math. 68 (3): 694–719. arXiv:q-bio/0610048. doi:10.1137/060673254. S2CID 14655317. Retrieved 2008-06-09.
  21. ^ Ahmed, S.; Karsiti, M.N. (2007), "A testbed for control schemes using multi agent nonholonomic robots", 2007 IEEE International Conference on Electro/Information Technology, p. 459, doi:10.1109/EIT.2007.4374547, ISBN 978-1-4244-0940-2, S2CID 2734931
  22. ^ "OMG Document – orbos/97-10-05 (Update of Revised MAF Submission)". Retrieved 2019-02-19.
  23. ^ Ahmed, Salman; Karsiti, Mohd N.; Agustiawan, Herman (2007). "A development framework for collaborative robots using feedback control". CiteSeerX {{cite journal}}: Cite journal requires |journal= (help)
  24. ^ "IEEE IES Technical Committee on Industrial Agents (TC-IA)". Retrieved 2019-02-19.
  25. ^ Leitão, Paulo; Karnouskos, Stamatis (2015-03-26). Industrial agents : emerging applications of software agents in industry. Leitão, Paulo,, Karnouskos, Stamatis. Amsterdam, Netherlands. ISBN 978-0128003411. OCLC 905853947.
  26. ^ "Film showcase". MASSIVE. Retrieved 28 April 2012.
  27. ^ Leitao, Paulo; Karnouskos, Stamatis; Ribeiro, Luis; Lee, Jay; Strasser, Thomas; Colombo, Armando W. (2016). "Smart Agents in Industrial Cyber–Physical Systems". Proceedings of the IEEE. 104 (5): 1086–1101. doi:10.1109/JPROC.2016.2521931. ISSN 0018-9219. S2CID 579475.
  28. ^ Xiao-Feng Xie, S. Smith, G. Barlow. Schedule-driven coordination for real-time traffic network control. International Conference on Automated Planning and Scheduling (ICAPS), São Paulo, Brazil, 2012: 323–331.
  29. ^ Máhr, T. S.; Srour, J.; De Weerdt, M.; Zuidwijk, R. (2010). "Can agents measure up? A comparative study of an agent-based and on-line optimization approach for a drayage problem with uncertainty". Transportation Research Part C: Emerging Technologies. 18: 99–119. CiteSeerX doi:10.1016/j.trc.2009.04.018.
  30. ^ "Generation Expansion Planning Considering Investment Dynamic of Market Participants Using Multi-agent System - IEEE Conference Publication". 2019-12-17. doi:10.1109/SGC.2018.8777904. S2CID 199058301. {{cite journal}}: Cite journal requires |journal= (help)
  31. ^ "Distributed Multi-Agent System-Based Load Frequency Control for Multi-Area Power System in Smart Grid - IEEE Journals & Magazine". 2019-12-17. doi:10.1109/TIE.2017.2668983. S2CID 31816181. {{cite journal}}: Cite journal requires |journal= (help)
  32. ^ a b "AI can predict your future behaviour with powerful new simulations". New Scientist.
  33. ^ Gong, Xiaoqian; Herty, Michael; Piccoli, Benedetto; Visconti, Giuseppe (3 May 2023). "Crowd Dynamics: Modeling and Control of Multiagent Systems". Annual Review of Control, Robotics, and Autonomous Systems. 6 (1): 261–282. doi:10.1146/annurev-control-060822-123629. ISSN 2573-5144. Retrieved 4 May 2023.
  34. ^ Hallerbach, S.; Xia, Y.; Eberle, U.; Koester, F. (2018). "Simulation-Based Identification of Critical Scenarios for Cooperative and Automated Vehicles". SAE International Journal of Connected and Automated Vehicles. SAE International. 1 (2): 93. doi:10.4271/2018-01-1066.
  35. ^ Madrigal, Story by Alexis C. "Inside Waymo's Secret World for Training Self-Driving Cars". The Atlantic. Retrieved 14 August 2020.
  36. ^ Connors, J.; Graham, S.; Mailloux, L. (2018). "Cyber Synthetic Modeling for Vehicle-to-Vehicle Applications". In International Conference on Cyber Warfare and Security. Academic Conferences International Limited: 594-XI.

Further reading[edit]