4. Conclusion

There are three categories of methods for diagnosing discrete-event systems:

• centralized diagnostic methods ;

• decentralized diagnostic methods ;

• distributed diagnostic methods.

In centralized diagnostic methods, a single diagnostic module, called the "diagnoser", is associated with the overall system model. The diagnostician collects the various information from the system before making a final decision on its operating status. Decentralized diagnostic methods are based on a global system model with several local diagnosticians. Each local diagnostician receives his or her specific observations and makes a local decision based on his or her local observations.

The major drawback of this type of method is the need...