Fuzzy sets are a well established method of describing uncertainty, imprecision and vagueness.
A FIS is one that uses fuzzy sets to make decisions or draw conclusions. There are a huge number of applications of FIS including steel manufacturing, robotics, washing machine control, aircraft flight control, robot control, car speed control, power systems and nuclear reactor control, fuzzy memory devices and the fuzzy computer. In particular, fuzzy system developers have to adopt some approach for determining membership functions. Attaching numbers to features of a problem is notoriously difficult and experts in a domain are unlikely to arrive at a consensus. Also, the traditional methods for inferencing with if-then fuzzy rules only adopt one of the normal forms thus not capturing the inherent uncertainty in the process.