Study On The Model Construction Of Digital Library Based On Grid Technology

In resent years, the technology of grid computing and Digital Library has experienced great development. Because of the consistency of their research object and research direction, we often introduced the technology of grid computing when we constructed a Digital Library System. We can say that the technology of grid computing has provided powerful conditions and strongly supports.In the Grid environment, the Digital Library is a type of information resources sharing system based on uniform standards and criterions, and the construction of the DL is adopted advanced grid technology. The aim is to provide a unified, transparent and efficient information service platform to the users, and to realize the interconnection and intercommunication of the Digital Library resources and services.The characteristic of the resources in the Digital Library Grid is distributed, heterogeneous, dynamic and autonomous. These resources maybe belong to an organization or individual, and exist in variety of heterogeneous platforms. Digital Library Grid must organize and connect thesse distributed information resources effectively. Through various means and methods, these resources have been integrated into an identity information resource system. Users can access to the digital library resources through a unified interface in the grid.Based on the development of the technology of the Digital Library and the grid computing, this dissertation discusses the grid technology related to the use of construction of Digtial Library. The purpose of the research is to find out the construction model of Digital Libaray based on Grid. This study has an important role in guiding the development direction of future Digtial Library, and has played a positive and promoted role for using the grid computing technology in the construction of Digital Library.This dissertation contains eight chapters, thereinto which the third, the fourth, the fifth, the sixth and the seventh are core contents. The main contents of the dissertation are as followings:The first chapter makes out the background, motive, contents, and framework of the research, and emphasizes that the research content is the inevitable result when the Digital Library develops to a certain stage, and that is the inevitable choice when the Digital Library attempted to fit the change of the user's information behavior, and that is the inevitable requirement when the Digital Library solves the problem of Information islands. Furthermore, this chapter also describes the contents of this research, research methods and research innovations.The second chapter summarizes the related research and literature about grid computing and Digital Library, and reviewes the foreign and domestic research status of Digital Library based on grid, and points out the contributions and shortcomings of the current research.The third chapter firstly analyzes the classical architecture of grid, and then compares the types of the grid-based digital library architectures. As a basis for this, the dissertation designs a personalized service oriented hierarchical architecture of grid-based digital library. This architecture is divided into four layers:resource layer, scheduling layer, application layer and portal layer.The fourth chapter expounds the composition and characteristics of Digital Library resources on the grid, and analyzes the general model of the resource organization in traditional digital library, and designs a new grid-based digital library resources organization model:Global/Local double-layer resource pool model. Finally, the dissertation tries to explore the process and the tools of the resources organization.The fifth chapter puts forward targets of resource discovery in digital library grid. Currently, resource discovery have four models:centralized type, distributed type, mixed type and hierarchical type. Based on the detailed analysis and evaluation, the dissertation proposes an improved method aimed at hierarchical resource discovery model and describes its principle and algorithm, as well as the effect of improved method.The sixth chapter analyzes the characteristics and purposes of information service in the grid-based digital library, and puts forward in the grid environment the service model of digital library is facing personalized integration service model. Personalized service emphasizes that the services should be focus on the user's demand, and integration service embodies that the user's access to the resources is seamless, transparent, and one-stop style. Users can achieve any resources needed anytime and anywhere. There have six contents in the personalized integration service model:individualized information customization and pushing service, collaborative digital reference services, self-adaptive learning services, intelligent tutor services, scientific collaboration services, knowledge increment services.The seventh chapter firstly represents the security features of the digital libary in gird environment, and then describes the main problems and key technologies in grid-based digital library access control model. Furthermore, the disseratation analyzes four access control models that is respectively DAC (Discretionary Access Controls), MAC(Mandatory Access Controls), RBAC(Role-based Access Control) and TBAC(Task-based access control).At last the disseratation indicates that combination of Task-based and Role-based access control model is the ideal choice when we construct a large-scale digital library grid.The eighth chapter summarizes the main conclusion of this dissertation, and points out expectations of continuous research in this field.Innovations of the research include the following aspects:(1) Designed an Architecture of Grid-based Digital LibraryAccording to the features of grid-based digital library and the hierarchical structure of grid resource management system, the dissertation designed a personalized service oriented hierarchical architecture. This architecture embodies the integration of grid heterogeneous environment, and emphasizes the personalized service function of the digital library. The bottom layer is resource layer, as the basic support of the architecture, which provides plentiful digital resources and computing power; the second layer is scheduling layer, whose role is shielding the heterogeneous environment, arranging the program course and monitoring the grid security; the third layer is application layer, which is mainly to solve the problem of resource organization, users management and data mining and so on; the top layer is portal layer, which directly provides various personalized service functions to users.(2) Designed a Resources Organization Model of Grid-based Digital LibraryResources organization provides work preparation to grid-based digital library service, and it is the foundation of user's information acquisition. The features of the resources in grid-based digital library are tremendous, distributed, heterogeneous, dynamic and autonomous. The dissertation analyzes the general model of the resource organization in traditional digital library, and designs a new grid-based digital library resources organization model:Global/Local double-layer resource pool model. Dividing the resources into global domain and local domain, this model realizes the hierarchical management, improved the security and efficiency of the resource finding and reduced the communication bottleneck.(3) Improved the hierarchical resource discovery modelThe grid scale more large the grid net structure more complex. Resource discovery is one of the key techonology and plays a crucial impact in the grid resource sharing. The efficiency of the resource discovery function directly decides the capability of the grid. Based on the detailed analysis and evaluation, the dissertation improved the hierarchical resource discovery model. Improved model introduces the concept of high-bandwidth node and low-bandwidth node, and inherites advantages of the original model. It also enhanced flexibility and expandability, improved efficiency of resource discovery.(4) Designed a Service Model of Grid-based Digital LibraryBased on the analysis of characteristics and purposes of service model in the grid-based digital library, the dissertation puts forward a facing personalized integration service model, which consists of six contents:individualized information customization and pushing service, collaborative digital reference services, self-adaptive learning services, intelligent tutor services, scientific collaboration services and knowledge increment services.(5) Combined the Task-based and Role-based Access Control ModelBecause of security threats facing to grid-based digital library, the access control model needs to realize general service, intelligent auxiliary, global uniformity and autonomous control. According to specific requirements and their own features of the grid-based digital library, the disseratation indicates that combination of Task-based and Role-based access control model is the ideal choice when we construct a large-scale digital library grid. This model have double speciality, on the one hand it can config multiple security policies through duty separation and inheritance relationship of roles; on the other hand it can add some reference value of system task status.