Fuzzy logic was invented by Zadeh [9] in 1965 for handling uncertain and imprecise knowledge in real world applications. It has proved to be a powerful tool for decision-making, and to handle and manipulate imprecise and noisy data. The first major commercial application was in the area of cement kiln control. This requires that an operator monitor four internal states of the kiln, control four sets of operations, and dynamically manage 40 or 50 "rules of thumb" about their interrelationships, all with the goal of controlling a highly complex set of chemical interactions. One such rule is "If the oxygen percentage is rather high and the free-lime and kiln-drive torque rate is normal, decrease the flow of gas and slightly reduce the fuel rate".