Modeling Complex Systems by Diana Stirling A Review and Discussion of the Paper James Hornage

Complex Adaptive Systems Characteristics of Complex Adaptive Systems: They persist in spite of changes in the diverse individual components The interaction between the components is what is responsible for the persisitence of the system The system engages in adaptation or learning.

The Concept of Co-Evolution Kauffman (1995) argues that A living system must first be able to strike an internal compromise between malleability and stability. Co-evolution is necessary because when an agent changes, the environment around that agent changes as well. Co-evolution concepts underlie the premise that there is an optimum size and number of patches to maintain maximum response ability.

Putting the Systems in Perspective Size and scope can range from neurons to social systems Agent (system) is likely unaware of the extent of the entire system Systems need only to provide excellent solutions as opposed to optimal solutions Let not the pursuit of the perfect solution stand in the way of a perfectly good solution.

The Power and Difficulty of Modeling The Power Modeling complex systems provides into problems particularly when people have trouble visualizing them. Modeling provides a way to understand the impact of variables in a clear manner The Difficulty Disagreements in definition can arise, such as the difference between Gell-Manns terminology and Hollands terminology for an adaptive agent

Modeling Tools Starlogo and Netlogo provide users with the opportunity to see self-organization in a visual model Both products use the Logo language, which was developed out of MIT in order to teach the basics of computing to children The main components of these models are turtles, patches, and the observer.

Starlogo FireFlies

Starlogo Ants

Summary Complex adaptive systems: Involve agents, whose behavior is motivated largely by reaction to the local environment Oscillate between order and chaos, which actually provides for stability and flexibility Rely on excellent solutions rather than the optimum solution Base their judgment about a solution as excellent by creating a schemata based on activities that are regularly identified with success.

Discussion What other models do you think would be interesting based on the Ants and Fireflies models from Starlogo? What are your thoughts on the concept of co- evolution? It seems the environment depends on the agent almost as much as the agent depends on the environment? Do you have a different way that you would define or describe the term complex adaptive systems?