From the Introduction:
Soft computing represents that area of computing adapted from the physical sciences. Artificial Intelligence techniques within this realm attempt to solve problems by applying physical laws and processes. This style of computing is particularly tolerant of imprecision and uncertainty, making the approach attractive to those researching within 'noisy' realms, where the signal-to-noise ratio is quite low. Soft computing is normally accepted to include the three key areas of Fuzzy Logic, Artificial Neural Networks, and Probabilistic Reasoning (which includes Genetic Algorithms, Chaos Theory, etc).
Available at: http://works.bepress.com/clarence_tan/5/