Stigmergy

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Stigmergy is a mechanism of spontaneous, indirect coordination between agents or actions, where the trace left in the environment by an action stimulates the performance of a subsequent action, by the same or a different agent. Stigmergy is a form of self-organization. It produces complex, apparently intelligent structures, without need for any planning, control, or even communication between the agents. As such it supports efficient collaboration between extremely simple agents, who lack any memory, intelligence or even awareness of each other.

Stigmergy was first observed in social insects. For example, ants exchange information by laying down pheromones on their way back to the nest when they have found food. In that way, they collectively develop a complex network of trails, connecting the nest in the most efficient way to the different food sources. Other eusocial creatures, such as termites, use pheromones to build their complex nests by following a simple decentralized rule set. Each insect scoops up a 'mudball' or similar material from its environment, invests the ball with pheromones, and deposits it on the ground. Termites are attracted to their nestmates' pheromones and are therefore more likely to drop their own mudballs near their neighbors'. Over time this leads to the construction of pillars, arches, tunnels and chambers.

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[edit] History

The term was introduced by French biologist Pierre-Paul Grassé in 1959 to refer to termite behavior. He defined it as: "Stimulation of workers by the performance they have achieved." It is derived from the Greek words stigma (mark, sign) and ergon (work, action), and captures the notion that an agent’s actions leave signs in the environment, signs that it and other agents sense and that determine and incite their subsequent actions [1].

Later on, a distinction was made between the stigmergic phenomenon, which is specific to the guidance of additional work, and the more general, non-work specific incitation, for which the term sematectonic communication was coined[2] by E. O. Wilson, from the greek words sema (sign, token), and tecton (craftsman, builder) : "There is a need for a more general, somewhat less clumsy expression to denote the evocation of any form of behavior or physiological change by the evidences of work performed by other animals, including the special case of the guidance of additional work."

Stigmergy is now one of the key[3] concepts in the field of swarm intelligence.

[edit] Applications

Stigmergy is not restricted to eusocial creatures, or even to physical systems. On the Internet there are many emergent phenomena that arise from users interacting only by modifying local parts of their shared virtual environment. Wikipedia is an example of this. The massive structure of information available in a wiki,[4] or an open source software project such as the Linux kernel[4] could be compared to a termite nest; one initial user leaves a seed of an idea (a mudball) which attracts other users who then build upon and modify this initial concept, eventually constructing an elaborate structure of connected thoughts.[5][6]

The term is also employed in experimental research in robotics, multi-agent systems and communication in computer networks. In these fields there exist two types of stigmergy: active and passive. The first kind occurs when a robotic or otherwise intelligent "agent" alters its environment so as to affect the sensory input of another agent. The second occurs when an agent's action alters its environment such that the environmental changes made by a different agent are also modified. A typical example of active stigmergy is leaving behind artifacts for others to pick up or follow. An example of passive stigmergy is when agent-A tries to remove all artifacts from a container, while agent-B tries to fill the container completely.

In addition the concept of stigmergy has also been used to describe how cooperative work such as building design may be integrated. Designing a large contemporary building involves a large and diverse network of actors (e.g. architects, building engineers, static engineers, building services engineers and etc.). Their distributed activities may be partly integrated through practices of stigmergy.[7][8]

[edit] See also

[edit] References

  1. ^ "Definitions of stigmergy." From a special Issue of Artificial Life on Stigmergy. Volume 5, Issue 2 / Spring 1999. http://www.stigmergicsystems.com/stig_v1/stigrefs/article1.html
  2. ^ Sociobiology : The New Synthesis, E.O. Wilson, 1975/2000, p.186
  3. ^ Parunak, H. v D. (2003). Making swarming happen. In Proc. of Conf. on Swarming and Network Enabled Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR), McLean, Virginia, USA, January 2003.
  4. ^ a b Infoworld: A conversation with Steve Burbeck about multicellular computing
  5. ^ Heylighen F. (2007). Why is Open Access Development so Successful? Stigmergic organization and the economics of information, in: B. Lutterbeck, M. Baerwolff & R. A. Gehring (eds.), Open Source Jahrbuch 2007, Lehmanns Media, 2007, p. 165-180.
  6. ^ Rodriguez M.A. (2008). A Collectively Generated Model of the World, in: Collective Intelligence: Creating a Prosperous World at Peace, eds. M. Tovey, pages 261-264, EIN Press, ISBN: 09715-6616X, Oakton, Virginia, November 2007
  7. ^ Christensen, L. R. (2007). Practices of stigmergy in architectural work. In Proceedings of the 2007 international ACM Conference on Conference on Supporting Group Work (Sanibel Island, Florida, USA, November 04 - 07, 2007). GROUP 2007. ACM, New York, NY, 11-20.
  8. ^ Christensen, L. R. (2008). The Logic of Practices of Stigmergy: Representational Artifacts in Architectural Design. In Proceedings of the 2008 ACM Conference on Computer Supported Cooperative Work (San Diego, CA, USA, November 8-12, 2008). CSCW '08. ACM, New York, NY, 559-568.

[edit] External links

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