Stigmergy

Presented by Francis Heylighen

Concept

........... --- stimulates to work ---> ...........

MEDIUM ------------------ AGENTS

........... <--- act on, change ------ ...........

The wokr of the agent(s) leaves a trace that is registered in the medium, where it is perceivable by other agents, stimulating them to further improve or extend the work that needs to be done. This is feedback cycle that is mostly positive: more work being done leads to more further work being done. The feedback can be negative when an agent corrects or removes a mistake made by previous agent.

Important dimensions of stigmergy

• Lifetime/ Evaporation: how long does the trace last in the absence of further work?
  • defined evaporation for ant foraging: food sources get quickly exhausted, ad therefore the pheromone trace becomes outdated
  • no evaporation for SO encyclopedia:
• Qualitative versus quantitative stigmergy
  • links in Wikipedia to non-exisiting articles
• Number of agents
• Local versus global memory
• Shortcomings of stigmergy
  • Medium: You need a medium that is sufficiently stable (cannot use air as medium)
  • Medium: Medium must be accessible by all agents
  • Asynchronous nature (can also be an advantage)
  • Reliability
• A list of applications would be needed