Research On Coordination Model For Open Distributed Environment

With the development of open distributed computing technology, the most of distributed application systems run under open distributed environment that is continuously changing and expanding. Due to the inherent environment distributing, dynamicity and users'requirements that are continuously evolving, the distributed systems become more dynamic, complex and instable. To solve these problems, the paper researches on the coordination model with dynamic, open and more flexible interactions using software coordination technology. The model provides a theory framework and technology support for the development of open distributed systems.Firstly, the background and the state of the art of software coordination are surveyed. The related work in the areas of software middleware, coordination models and languages and programmable coordination technology, and especially that software development and running support technology for open and dynamic distributed environment is discussed. The advantages and disadvantages of these technologies are pointed out. The influence that is contributed by Actor model to open distributed systems is analyzed.Secondly, in order to face the dynamic change of interaction topology and real-time constrain among autonomous entities in open distributed real-time system, a time and interaction coordination model driven by events is presented. The two different categories of entities: time coordinators and communication coordinators are separated from traditional autonomous entities based on the separation of concerns. An implementation framework of the model is builded by using exicting programmabl technology. An application example to a vehicle navigation system is illustrated that the model is validity and feasibility.Finally, an ERC coordination conceptual model is described by introducingthe concept of the role in the time and interaction coordination model. The non-functional behavior is separated from traditional entities based on the principle of separation of concerns, and is abstracted as coordinators and roles. The traditional entities are evolved as true functional entities. The model is consisted of coordination layer, role layer and entity layer. A dynamic binding method with flexibility and adaptability is presented using the technologies that ERC model provide. The method is described on the specific details. The feasibility of ERC model and dynamic binding methods is demonstrated by studying a case.