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Research On Service-Oriented Mobile Agent Group Communications

Posted on:2006-05-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:W XuFull Text:PDF
GTID:1118360152487502Subject:Computer software and theory
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Web Service is becoming a standard-based computing platform and supports construction of loosely coupled wide-area distributed systems. By integrating Web Service and Business Process Management (BPM), Service Cooperation Middleware (SCM) aims to implement models and mechanisms that can adjust their configurations and behaviors to be adaptive to environments and system requirements. As a result of that, SCM provides a feasible way to achieve an "on-demand" distributed enterprise computing environment.SCM addresses on distributed and variable services, which can take advantages of mobile agent technology, especially the capabilities of autonomy and cooperation of distributed mobile agents. As an independently migrating distributed computing entity, mobile agent can alleviate network load, support disconnected computing, dynamically adapt to networking environments, etc. Therefore, mobile agent has been adopted in many application areas, such as mobile computing, cooperative computing and e-commerce. In the scenario of service cooperation, SCM can organize distributed Web Services by utilizing the intelligibility and negotiability of mobile agents, and implement business requirements of enterprise computing through interaction and cooperation at the granularity of service.However, there are several main obstacles to apply mobile agent technology in SCM, one of which is the group communication for mobile agents. Mobile agent group communications provide the fault-tolerant capability for Web Services and the group-based communication approach for service cooperation. Two fundantmental components of mobile agent group communications are multicast and membership management. But current researches of mobile agent communications focus on one-to-one unicast protocols and lacks of practical solutions for mobile agent group communications. In this thesis, to solve mobile agent group communications issues in SCM, we intend to study service-oriented mobile agent group communications.First, we propose a totally ordered multicast protocol for mobile agents, named MATOM. In MATOM, we use the clustering mechanism and the logical ring structure to achieve atomicity and total ordering properties of mobile agent multicast communications, which ensure that all mobile agents of the system can react toevents (messages) in an universal consistent order. We prove the correctness of MATOM and analyze its performance issues through simulations.Based on MATOM, we present a fault-tolerant membership management approach for mobile agents. This approach defines membership functions by the clustering mechanism, i.e. the membership protocol will handle join/leave requests of mobile agents to corresponding agent clusters for adding/removing mobile agents in/from clusters. Meanwhile, we design a fault-detector for the membership protocol to detect and remove possible crashed mobile agents. The principles of the proposed fault-detector have been illustrated and its correctness has been proved.Thus MATOM and the fault-tolerant membership approach compose a mobile agent group communication system, called GCS-MA. We address the application of GCS-MA in SCM at two subjects: the mobile agent-based fault-tolerant model for composite Web Service and the mobile agent group-based service cooperation.Existing fault-tolerant Web Services emphasize the fault-tolerant extensions of Web Service related standards. Because these standards are evolving and have some compatibility problems, approaches used in current works cannot provide a practical way to implement a fault-tolerant mechanism for Web Service. So we propose a mobile agent-based fault-tolerant model for composite Web Services, called MAFTM, by using GCS-MA at the system level. We discuss the relationship between workflow and composite Web Service. Then we present MAFTM model including failure models, the replication mechanism, "exactly once" semantics and the consistent algorithm. Also, we prove the correctness of MAFTM.At the end of this thesis, we describe cooperation concepts and technologies of SCM. T...
Keywords/Search Tags:Mobile Agent, Group Communication, Reliable Multicast, Membership Management, Totally Ordered Multicast, Fault-Tolerant Model, Composite Web Service, Service Cooperation
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