Saturday, 17 July 2010

Architecture of complex systems

How is a complex system architectured? To start to answer this though question is necessary firstly to consider that it has large number of relatively simple elements working parallely, which provides robustness and efficiency. Secondly, the system works by simultaneous exploration of many possibilities or pathways, in which the resources are made available according to the probability of success. Many different possibilities are explored simultaneously, but with different depth and speeds. In this process, information is used to evaluate the probability of success and to invest important resources in what is worth exploring.
A good example is provided by Melanie Mitchell in "Complexity: a guided tour". The immune system must determine which regions of the exploratory universe of pathogen shapes will be screened. There are trillions of lymphocytes in the body at any given time, most of them can uniquely identify a specific pathogen shape (or antigen). The shape ranges that are most successful are given more exploration resources: the immunological system increases the number of lymphocytes specifically compromised to that shape range. Thus, the system is able to focus on the most promising pathogens, while never neglecting to explore new possibilities.

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