Research On Reliable Multicast Communication Mechanism In Migrating Workflow System

The migrating workflow is a new technology applying mobile computing to workflow management, which is a new direction within the research of workflow management. Migrating workflow management engine, migrating instance and work station are three main elements of migrating workflow management system.Workflow engine complete the definition of workflow process, the generation of migrating instance and the coordination of more migrating instances.Work station refers to anchorage and network associated with it,wich is the operation place of migrating instance. Migrating instance is constructed by the mode of mobile agent, created by workflow engine or work station, is the main implementator of task, to complete one or more tasks by using the local resources of work station. Workflow process is completed by a number of migrating instances' migration and collaboration. Reliable Multicast System is a key protection mechanism to realize the cooperation of migrating instance, which is also an important issue of the migrating workflow research.From the research results of distributed cooperation and mobile agent multicast, based on the characteristics of migration flow, a multicast system model based on token is proposed. A multicast protocol is designed to ensure the realization of the entire sequence of semantic reliable multicast according to the model. The data structure of the protocol and the corresponding algorithm are given by this paper in detail.The correctness of the protocol is also proved in this paper. The protocol can resolute the the overall inconsistency problems of the multicast effectivly. The entire message sequence of the protocol is realized by the use of the token, ensure the reliable transmission by the appropriate design of buffer mechanisms, effectivly solute the overall inconsistency of mulicast, and ensure a consistent state of mukticast. According to the multicast model, a fault-tolerant group member management mechanism based on hierarchical structure is designed in this paper.The agreement to join the group or from the group or the fault management is effectivly realized in the mechanism. This hierarchical structure is also conducive to expansion of the multicast system, and also has highly flexible.For the possible failure of members in multicast, a random heart failure detection method is proposed, which can detect the error members in time and realize the error control of the multicast system.First, the basis knowledge of the migrating workflow and multicast is outlined in this paper. Latter, according to the migrating workflow mode, a mulicast system of migrating workflow based on token is designed, the whole sequence of multicast protocol is also designed, the data structure of the protocol and the corresponding algorithm are gived too. Then, a fault-tolerant member management structure based on the hierarchical structure is proposed and a random heartbeat fault detection method based on the location of the work is designed, the method's correctness is also analysised in this paper.