This chapter presents the specification of the WAFER-STATE-SERVER It deals with design and implementation issues of the WAFER-STATE-SERVER library. First the mechanism to configure the WAFER-STATE-SERVER is briefly discussed. Then, the basic modules and all available implementations of the modules are presented. Finally, some implementation details concerning the chosen programming language are given. The WAFER-STATE-SERVER classes were implemented in the C++ [30,31] programming language.