@Article{werfel06a,
  author =	 {Justin Werfel and Radhika Nagpal},
  title =	 {Extended Stigmergy in Collective Construction},
  journal =	 {{IEEE} Intelligent Systems},
  year =	 2006,
  volume =	 21,
  number =	 2,
  pages =	 {20--28},
  abstract =	 {A swarm of agents can coordinate its components'
                  behavior by modifying the environment, a practice
                  known as stigmergy. Augmenting the capabilities of
                  environmental elements to let them store, process,
                  or communicate information can increase the power of
                  this approach, in what we call extended stigmergy. A
                  swarm of robots can use either approach to
                  automatically build 2D, solid, user-specified
                  structures out of square building blocks. A
                  comparison of the relative performance of three
                  construction algorithms that use building blocks
                  with different capabilities demonstrates the
                  usefulness of extended stigmergy. That approach can
                  increase the availability of nonlocal information to
                  the mobile robots, and thereby improve construction
                  time and the opportunity to exploit the swarm's
                  parallelism.This article is part of the special
                  issue on Self-Managing Systems.},
  keywords =     {multiagent biology},
  url = 	 {http://jmvidal.cse.sc.edu/library/werfel06a.pdf},
  doi = 	 {10.1109/MIS.2006.25}
}