Fuzzy Inference Systems (FIS) have the advantage of relying on the properties of Fuzzy Logic to represent imperfect information so gradually, and manipulate them from a linguistic description. This exibility of representation is more signicant for the study of complex systems. Our aims are to propose a formal approach for describing FIS as a Discrete Event System (DES), and to extend a DES in order to use the many advantages oered by FIS: exibility, easy implementation, robustness... In this paper, we present the extension of Discrete EVent system Specication (DEVS) formalism to represent FIS, and we propose a modular approach (DEV-FIS) to use several optimization methods. We focus mainly on the used new aproach about using genetic algoritm in order to optimize the FIS.