Research On Dynamic Reconfiguration Of Web Serivces Oriented Software

Along with the appearance and rapid improvement of SOA (Service oriented architecture), it has been one of the most promising computing paradigm in the Internet era. Also, the SOA-based software has been more popular and one of the most promising software paradigms at present. The SOA-based software is by nature heterogeneous, dynamic and collaborative, and this leads to new challenges for its management and maintenance. But dynamic reconfiguration technology, has been one of the most dominant software maintenance technologies, can be a feasible way to solve the problems. Meanwhile, it can not only help the SOA-based software improve their availability, reliability and robustness, but also help SOA break the bound which prevents it from getting the popular acceptance.From the macro-level of the SOA-based software, the paper mainly researches on the following three problems:building the software architecture that supports dynamic reconfiguration, verifying the correctness of dynamic reconfiguration, and execution and management of dynamic reconfiguration. The major work and contributions are as follows:First, we propose a software architecture that supports dynamic reconfiguration. A SOA-based software architecture supported dynamic reconfiguration is proposed. It is constructed using reflection technology and composed of the meta-level and the base-level. The meta-level and the base-level are associated in the form of cause and effect. The meta-level can be regarded as the run-time architecture of the SOA-based software and capture the state of the SOA-based software during the run-time and the information of structure. It is composed of the meta-structure level, the meta-link level, the services discovery level and the meta-service level. These levels, which are well interconnected and cooperate with each other, are the key to implement the dynamic reconfiguration. In addition, the base-level is composed of the physical Web services.Second, we propose the approach for modeling the large-granularity Web services and verifying the correctness of the dynamic reconfiguration based on the notion of the substitutability and compatibility of Web services. Along with more large and coarse granularity services appear across the Internet continuously. Presently, enterprises and researchers have widely accepted the new form of Web services. We propose the notion of interface inverted dependence to divide the large-granularity services into some atomic services. In order to model Web services, we regard a Web service as two different views:external behavior and internal behavior, and then introduce the Martin_Lof's type theory to formalize the Web services. Our method models not only the Web services but also the business logic of the SOA-based software.Based on. the above work, we propose the approach for verification of the correctness of the reconfiguration based on the substitutability and compatibility of Web services. Generally, for the SOA-based software, the main operations of its dynamic reconfiguration include:service addition, service deletion and service replacement. The correctness can ensure the SOA-based software can work as same as usual after modified by these operations. Thus, it is a key to ensure the correctness of every operation. The substitutability and compatibility can solve the problem. We analyze the characters of the whole external and internal behavior and the partial external and internal behavior and propose the definition of the substitutability and compatibility. We give the service behavioral types, its subtyping and dual rules to judge the substitutability and compatibility. Thus, our method translates the verification of the substitutability and compatibility into judging the subtype of the services behavioral type by type checking.Third, we propose the approaches for the functional dynamic reconfiguration oriented Web services composition and the non-functional dynamic reconfiguration oriented the selection of the reconfiguration objective. The approach for the functional dynamic reconfiguration oriented Web services composition is to solve the functional reconfiguration disability caused by unable to find the suitable candidate services. Our approach is entitled proofs-as-composition. Because the behind idea of our approach is proofs-as-programs. Based on it, we can compose the existing large-granularity services by proving theorems. The main idea of the method is as follows. Given a set of existing Web services and the requirements in term of extended OWL-S, we use dependent record type to describe formally all existing Web services as rules and the requirements as the propositions; the method completes a composition of the large-granularity services that satisfies the user requirements by proving the propositions.During run-time, the delivered QoS from a SOA based software maybe different from the new requirement of QoS or their original claims. In order to comply with the expected QoS, we need to reconfigure the SOA-based software by replacing its some component services with some candidates which has the better QoS. Thus, we should judge which some component services from the same software should be replaced when a new QoS constrains is proposed. We present a QoS driven dynamic reconfiguration of the SOA based Software to solve these problems. Our method tries to replace each individual component service according to the critical factors, and then if the all attempts failed, then replace multiple component services. In addition, the notion of the critical factor is introduced to show the contribution of the QoS of each component service from the same software to the QoS of the software. If the critical factor of one service is bigger, its contribution is greater and it should be replaced firstly. In this way, the complexity of the reconfiguration is reduced and only a few services are involved in the reconfiguration.Last, we design and implement a prototype of the SOA-based software dynamic reconfiguration-JTangSDR. We design the architecture of JTangSDR based on ESB(Enterprise Service Bus) and introduce the main functions, components, and core processes in the JTangSDR. JTangSDR is composed of the three main modules:basic services module, the SOA-based software integrate development module, and dynamic reconfiguration management module. These modules realize our method proposed in this thesis.