Stigmergy is a word used to describe a particular type of control: the control of the actions of a group of agents via a shared environment. Crucially, the agents do not directly communicate amongst themselves. Instead, each agent is caused (by its environment) to act upon and change the environment. These changes in turn alter the later actions of the agents.

The word stigmergy comes from the Greek stigma, meaning sting, and ergon, meaning work, capturing the notion that the environment is a stimulus that causes particular work (behavior) to occur. It was originally coined by zoologist Pierre-Paul Grassé,who explained the mound-building behavior of termites by appealing to the stigmergic control of the mound itself.

One of the appeals of stigmergy is that it explains how very simple agents create extremely complex products, particularly in the case where the final product (e.g. a termite mound) is extended in space and time far beyond the life expectancy of the organisms that create it. It is an important concept in the study of cooperation amongst members of robot collectives. It can also be used to describe the control structure of a standard production system architecture: the working memory of this architecture determines which productions take charge; they take charge and change memory; the changed memory then activates different productions.

Relevant Literature:

1. Theraulaz, G., & Bonabeau, E. (1995). Coordination in distributed building. Science, 269(5224), 686-688.
   
2. Theraulaz, G., & Bonabeau, E. (1999). A brief history of stigmergy. Artificial Life, 5, 97-116.
   

(Added October, 2009)