The Research And Implementation Of Object-Oriented Asynchronous Communication Middleware

Object-Oriented communication middleware aims to solve the problem of interconnection, intercommunication and interoperation in distributed heterogeneous environment. It makes implementation details transparent to the developers and improves the portability of the applications. Therefore, Object-Oriented communication middleware has been applied to various areas and has become one of the dominant distributed computing technologies. On the other hand, the form of distributed applications is changing with the rapid development of Internet. It moves from close, localized-oriented and static closely-coupled mode towards open, public and dynamic loosely-coupled mode. The mode transition challenges traditional Object-Oriented middleware greatly with respect to its synchronous communication mechanisms. In order to solve this problem, asynchronous communication method was introduced. It makes communications of distributed applications more effective. So far, asynchronous mechanism for Object-Oriented middleware becomes one of the research focuses. In this paper, we devoted to conceptual framework, asynchronous model, technologies and practices of asynchronous communication mechanism respectively. Firstly, we establish a comprehensive concept framework with layered structure for asynchronous communication of Object-Oriented middleware. Then we present a platform independent asynchronous model PIDOAM. And its mapping models Star-AP and Star-ATII are also given. Furthermore, we explore on enabling technologies of Publish/Subscribe communication and how to apply Star-AP into this kind of communication mode. Finally, we show the design and implementation of Star-Async, an asynchronous middleware system.Contributions of this paper are illustrated as follows:Firstly, this paper establishes a comprehensive concept framework for asynchronous communication of distributed object-oriented middleware. According to the framework, a layered asynchronous mechanism is defined with broker-based asynchronism, method-level asynchronism, message-level asynchronism and transport-level asynchronism. The substantial difference and association among these four mechanisms are clarified. Thus for the asynchronous communication mechanism, the glossaries are uniformed and the framework serves well as a theoretical guidance for researchers on mechanisms.Secondly, based on an abstract definition of distributed object-oriented middleware PIDOF, the paper presents an asynchronous model PIDOAM which is independent of concrete distributed object-oriented middleware. The mappings of this model to concrete distributed object-oriented middlewares are given also.Thirdly, we make research on technologies for decoupling time, space and control flow. Since time, space and control flow are coupled tightly, the synchronous communication can't provide well support for the applications which are wide-area network applications or need coordination of inter-organization and intra-organization. Therefore, asynchronous communication mechanism should aim at time, space and control flow decoupling. To decouple control flow, the model of Star-AP is presented which implements the asynchronous polling mechanism. The paper defines the syntax and semantic specification for polling mechanism. And the architecture of the model is discussed. Finally, we prove that the Star-AP model can satisfy the syntax and semantic specification of polling mechanism. To decouple time and control flow, the model ofStar-ATII is presented which implements asynchronous time-independent invocation mechanism. The architecture of Star-ATII model is discussed and the core algorithms are introduced. The paper also explores the way to integrate Star-ATII and MOM. Star-ATII model supports time-independent asynchronous invocation mechanism and disconnected operation, and can also effectively decouple both sides of communication. Consequently Star-ATII is well applied in wide-area network applications. As a kind of important asynchronous communication model, Publish/Subscribe communication model can decouple ti...