Abstract: The qualitative model-based fault diagnosis approach can depict the system configuration in qualitative model, and get the predicted behavior qualitatively. The system fault can be diagnosed by determining the differences between the model of an artifact and the artifact itself. This paper investigates the diagnosis mechanism, system modeling, advantages and disadvantages of the qualitative model-based fault diagnosis approach. Its progress, application, and trend developing are also addressed.

Key words: fault diagnosis, qualitative model, diagnosis mechanism, system modeling