Abstract: This paper proposed a new diagnosis approach based on the temporal relationship between events. In order to reduce the scale of the model, we first added some communication events to divide the global model. Then we deleted some useless road in the local models to reduce the space of states. According to the temporal relationship between communication events and observable events, we could get the diagnosability of the limited model and some properties. We used the properties to get the diagnosability of the local models, which avoids the high complexity of the synchronization operation. Finally we gave some examples to analysis the steps of the diagnosed process.

Key words: Model decomposition,Limited local modcl,Diagnosability