The Design And Research On Dlrf Based On Hierarchical And Fragmental Data Model

The thesis has analyzed the status and shortage of the resource environment in the distance learning. In order to effectively avoid the rebuilding and waste of the distance learning resources and to promote resource management, interoperability and extensibility capabilities, as well as to allow them to be combined for performing more complex operations, a standard reference architecture is needed. We have presented to apply the distributed database technology into the DLRF (Distance Learning Resource Framework) system. The thesis has mainly studied how to design and build a well-structured distributed resource framework. Now there are information gulfs in the distance learning resource systems. The degree of information sharing among different systems is low and the information lacks of proper structure. It is one of the reasons that have caused the rebuilding and waste of resources. But the resource construction and information sharing is a systemic engineering. In order that the system will run well, the process of system design must abide by formal design schema and architecture. Thus, if we can comply with the norm during the design process of the distance learning resource environment, it can greatly improve the information management and sharing capability. With the development of network technologies and distributed database technologies, they have provided the technology support for distance learning resource construction. Consequently, distributed database architecture is a natural choice for it. It is necessary and feasible to applied the distributed database technologies into our DLRF system considering the increasing expansion of education business and increasing resources. During the data model design process of the DLRF, we abide by the hierarchy and fragmentation principle in order to improve the reliability, availability, and local system autonomy of the system and to reduce the network flow. The hierarchy and fragmentation principle is a good means for solving complicated problems such as DLRF. The clear hierarchy framework is better for managing distributed system, effectively coordinating the sites residing at differentlocations, and then forming an integrated and well running distributed system. It is the key purpose of the DLRF.During the design process, we have firstly analyzed the requirements of the system, including business analysis, function analysis, non-functional analysis and the external constraints. Then we have expounded the design scheme involving the architecture and components and hierarchy information management method. In view of the diversity and multi-model of education system, it is often that different systems with different purposes may reasonably come to different interpretations about the same terms. Abide by the principles of "to first realize that different ones have the same cognizance about the same terms and then to realize information sharing", we use ontology to describe the critical terms in distance learning and to structuralize and to provide equivalence criteria, and at the same time it can effectively reduce the semantic conflicts and facilitate the interoperability among different data sources. It also has created conditions for in-depth information abstraction. The motivation behind the ontology practice is economic: there is benefit to doing things in a standard way and cost to doing things differently. Then we also have put forth an interoperable and sharing hierarchy model for distance learning. Though this model is put forward for distance learning, it also can be applied to other application domains, such as Web-based databases, digital library, data warehouses, data mining, etc. Considering the system performance demand, we have chosen a group of servers or cluster to establish the resource platform. The system are classified into 7 logical categories, each one executes different function. The data management has adopted the means of integrating the distributed control mechanism with the central control mechanism. We have applied the h...