Abstract: The increasing size and complexity of web service composition process has led to an amplified number of potential failures and makes it harder to ensure service reliability．To localize the faults of undefined service behaviors in service process,we proposed a diagnosis method based on Bayes and multi-faults logic reasoning．On the basis of modeling the service execution matrix by historical data,we combined multi-faults logic reasoning technique with the statistical technique to obtain the diagnosis candidates．By applying Bayes’ formula to compute the fault probability of each diagnosis candidate,our diagnostic method is able to obtain an asymptotically optimal diagnosis with increasing historical data．Experiments were conducted to evaluate the effectiveness of the method in diagnosing the web services with multi-faults.

Key words: Web service,Fault diagnosis,Logic reasoning,Bayes rule