【作者】 陈德华；

【导师】 乐嘉锦；

【作者基本信息】 东华大学 ， 控制理论与控制工程， 2006， 博士

【摘要】 基于构件的软件开发是一种重要的软件复用实践方法，它已经成为解决软件危机，提高软件生产效率和软件质量的一条切实可行的途径。在基于构件的软件开发方法中，构件库系统是一个至关重要的部分，扮演着极为关键的角色，是全面支持软件复用与基于构件的软件开发的重要基础设施。因此，构件库系统的研究和开发一直以来就是一项非常重要且有意义的工作，已得到学术界和产业界广泛的重视和关注，成为基于构件的软件开发相关领域的研究重点和热点。目前，传统的基于客户端／服务器(Client／Server，C／S)模式的构件库系统仍然是国内外学术界和产业界十分关注的研究重点。但是，随着软件复用与基于构件的软件开发实践的不断深入和发展，这种基于C／S模式的中心构件库越来越无法满足软件开发的需求。这是因为中心服务器的存储能力和效率毕竟是有限的，所能存储的软件构件的数量必然要受到限制，可是软件构件随着构件库应用的深入和推广却还在不断地增多；而且，当中心服务器访问量过大、负载过重时，服务器响应速度也必然大大地受到影响，开发人员获取、查询构件的效率必定降低，这也必将影响到构件库的推广和使用。针对传统的基于C／S模式的中心构件库所存在的问题，当前正被业界所重视的P2P(Peer-to-Peer，对等网络)技术可以发挥重要的作用。本文考虑到对等网络具有良好的技术特性和潜在优势，将对等网络前沿技术运用到构件库技术研究中，充分借鉴基于对等网络的文件共享系统领域中已取得的研究成果，提出利用P2P技术将网络中所有构件源节点互相连接组织起来，建设一个新型的基于对等网络的分布式构件库P2P-DCR(P2P-Based Distributed Component Repository)系统，并深入研究这种新型的构件库系统中若干个急需解决的关键技术问题。本文所进行的基于对等网络的构件库系统研究就对等网络前沿技术在构件库研究领域的应用进行了探索，是一次有意义的创新实践。本文的主要研究工作和创新成果可以总结概括为如下四个方面：第一，系统地阐述了P2P-DCR系统的体系结构和系统框架。本文通过总结基于对等网络的文件共享系统已有的研究成果，提出利用基于超级节点的网络架构作为P2P-DCR系统的体系结构，将网络中所有的构件源节点组织起来，从而形成一个规模庞大的分布式构件库系统；同时，本文还从构件查询引擎、构件索引目录结构和存储结构等方面详细论述了P2P-DCR系统框架；此外，本文还就P2P-DCR系统在实际运行中的动态演化行为作了详细的阐述。第二，系统地阐述了P2P-DCR系统的“泛播”式构件查找方案的机制和策略。本文根据P2P-DCR系统的基于超级节点的体系结构，首先详细论述了P2P-DCR系统中基本的“泛播”式构件查询路由机制；然后，在综合评析基本的“泛播”式查询路由机制局限性的基础上，提出一种改进的基于概率权值的查询消息转发策略的构件查询路由机制。第三，系统地阐述了如何在P2P-DCR系统中整合基于DHT的结构化构件查找技术，从而实现一种混合式的构件查找方案。本文针对P2P-DCR系统原有的“泛播”式构件查找方案在查找稀有构件的效率和质量上存在明显的弱处，提出了对P2P-DCR系统进行扩展，使其能够支持高效的混合式构件查找方案。这样，经过扩展后的P2P-DCR系统既继承了原有P2P-DCR系统的“泛播”式构件查找方案，又具有基于DHT的结构化构件查找方案，这样可以充分发挥不同构件查找方案的优势，弥补各自的劣势。第四，系统地阐述了P2P-DCR系统中构件查询访问控制的机制与策略，并提出一种基于信任的构件查询访问控制框架。本文在分析对等网络环境下的构件查询访问控制特点的基础上，通过对传统的访问控制模型进行拓展，提出一种基于信任的分布式构件查询访问控制框架。该框架将信任推荐模型及访问控制模式整合应用到基于对等网络的构件库系统中，力求为构件库用户提供良好的访问控制服务，而且尽量维持构件库系统的分布式结构。总之，本文提出并详细阐述了一种有别于传统C／S模式的基于对等网络的构件库P2P-DCR系统，着重于论述实现P2P-DCR系统的若干关键技术和模拟实验结果。本文的工作是建立在对相关理论和已有技术的详尽分析以及大量的实验测试结果之上的。实验结果表明，本文提出的基于对等网络的构件库技术不但能够支持大规模网络中构件的查找与共享，而且能高效地利用系统资源并有效地满足用户需求。更多还原

【Abstract】 As one of practical approaches of software reuse, Component Based Software Development (CBSD) has become an efficient and feasible solution to solve software crisis. It improves software development efficiency and software quality remarkably. In CBSD, Component repository plays an important role. It is the rather crucial infrastructure of CBSD and serves as the foundation for CBSD. Therefore, as one of rather significant and meaning research fields, the research and development of component repository has received more and more attention from the software academia and industry.Nowadays, the research and development of the traditional C/S-based component repositories is still the focus of the software academia and industry. However, with software reuse and CBSD developing, such C/S-based component repositories fail to meet the needs of software development. On one hand, as the component repositories developing and the clients mounting up, the number of components will increase rapidly. However, the limiting storage capacity of central servers is unable to store such great amount of components. On the other hand, when the central servers always operate in the state of overload, they tend to suffer from the bottleneck of efficiency of component retrieval.As to the problems of the traditional C/S-based component repositories, the P2P network technology provides a good’ solution. Considering the favorable technology characteristic and potential advantages of P2P network technology, we integrate P2P network technology into the research of component repositories. With referring to the researching fruits in the field of P2P-based file sharing systems, we propose a new P2P-based Distributed Component Repository, coined as P2P-DCR, which is constructed by organizing all the component-souring peers using P2P network technology. Furthermore, we have conducted an extensive study on some challenging technique problems for this new-stype component repository. The thesis has conducted the following researches and has achived the following contributions:1. We have systematically studied the network infrastracture and system framework of P2P-DCR.First, with the research fruits achived in the filed of P2P-based file sharing, we have proposed a superpeer-based network infrastrature to organize all the component-souring peers into a largely distributed component repository. Second, we have discussed detailedly the system framework of P2P-DCR which including component search engine, component indexing summary and storage structure; Finally, we have demonstrated detailedly the system evolution of P2P-DCR.2. We have systematically studied the flooding-based component search scheme in P2P-DCR.First, based on the network infrastrasture of P2P-DCR, we have discussed the basic flooding-based component search routing mechanism. Second, with the comprehensive analysis on the limitation of the basic flooding-based component search routing mechanism, we have proposed a new improved flooding-based routing mechamism which adapts a probabilistical weight-based message forwarding strategy.3. We have systematical studied the problem that how to integrate DHT-based component searching technique into the P2P-DCR.As to the shortcoming of the original flooding-based component search scheme in searching for rare components, we have proposed to extent the functionality of P2P-DCR to support the effective hybrid component search scheme. In this way, the extended P2P-DCR not only inherits the original flooding-based component search scheme but also possesses DHT-based structured component search scheme.4. We have systematically studied the mechanism and strategy of access control of component retrieval in P2P-DCR and proposed a trust-based component retrieval access control framework.Based on the analysis of the characteristics of access control in P2P-based component retrieval, we propose a trust-based component retrieval access control framework which is achived by expanding the traditional access control model. This framework integrates trust and recommendation model and access control model into P2P-based component repository, with the purpose of providing flavorable services for clients. Furthermore, the framework takes the decentralization of P2P-DCR into account.In a word, this thesis has proposed a P2P-based component repository, coined as P2P-DCR, which distinguishes from the traditional C/S-based repositories. This thesis also has systematically studied the design, key techniques and experimental results of P2P-DCR. All these contributions are achieved through a comprehensive study on the related theories, existing technologies and experimental results. Moreover, the experimental results have verified such a P2P-based component repository system can realize the search and sharing of components in a large distributed environment, and efficiently utilize the system’s resource as well.更多还原