Robust collaborative process interactions under system crash and network failures

With the possibility of system crashes and network failures, the design of robust client/server interactions for collaborative process execution is a challenge. If a business process changes its state, it sends messages to the relevant processes to inform about this change. However, server crashes and network failures may result in loss of messages. In this case, the state change is performed by the sending process in isolation, resulting in state/behaviour inconsistencies among processes and possibly undistinguished deadlocks. Our basic idea to solve this problem is to cache the response (in a synchronous request-response interaction) if the state of the process instance has changed by the request message. The possible state inconsistencies are recognised and compensated by state-caching and by retrying failed interactions.