Research On The Sharing Mechanism Of Educational Resources Based On P2P Grids

At present, primary and secondary schools of China have been established their own campus networks gradually, and accumulated a large number of digital teaching resources. However, the building of educational resources around is self-contained and can not achieve effective communication, bringing a tremendous waste of human and material resources. As an increasingly popular distributed computing platform, Grid provides an effective solution for the sharing of various resources. Data Grid is widely used in data-intensive computing, which provide rapid information retrieval and data access support for large amounts of distributed storage data resources. Therefore, the use of Data Grid technology can effectively integrate various types of educational resources dispersed geographically for authorized users, which can provide mechanism of distributed retrieval and sharing access. To build a high-performance educational resource grid can effectively solve the problem of educational resources sharing.As a kind of Data Grid, Educational Resource Grid has its own characteristics. Sharing of educational resources is faced to PCs. Resources were dispersed to be stored in teaching staff rooms of different schools, which can entry and exit grid system freely and have a high autonomy. Traditional organizational structures of data grid have been difficult to adapt to this change, while P2P Grids can solve this problem. P2P can be used as protocols for sharing and interacting data between grid nodes and provide the diversity of infrastructure and applications. Applications show that using P2P-based structure for resource discovery and information retrieval under the grid environment is a reasonable approach. This paper is to discuss the problem of educational resources sharing under environment above.On the basis of predecessor's work, the main research work and innovates can be described as follows:(1) A new architecture of network resource sharing based on P2P Grids for resources of primary and secondary schools is studied. Under the premise of resources storing in the distribution, related technologies of P2P and Grid are used to organize and manage these resources to achieve a wide range of high quality educational resources sharing. Aiming at characteristics of dynamic, autonomy and hierarchy of educational resource sharing nodes, an organizational structure of nodes based on the hierarchical expansion tree is proposed.(2) Information exchange norms and unified models for representation of information and resources are studied. For the characteristics of distribution and heterogeneous of educational resources, data sharing and exchange specifications of P2P Educational Resource Grid are studied and defined, which achieve the coordination, restructure and integration of various different structure of information and services.(3) The service calling model based on the agent cloud for the P2P Educational Resource Grid is studied. The model includes Persistent Object Manager, Service Call Manager and Service Exception Handler, which provides service instantiation, persistence, call forwarding and exception processing.(4) In view of the hierarchical expansion tree structure of the Educational Resource Grid, a distributed retrieval model of Educational Resource Grid based-on hierarchical P2P (DRM-HP2P) is proposed, which uses the Web Services technology to encapsulate the local resource retrieval of nodes, uses the P2P way to carry on the intra-domain retrieval, forwards retrieval requests to other domains through management node of this domain, then starts several intra-domain retrieval, and finally returns the merged results. Application shows that this model has a high efficiency.(5) Information retrieval and full-text retrieval for the Educational Resource Grid is studied, and a distributed full-text Top-k retrieval algorithm based-on Single-Dimension Semantic Vector Tuples to satisfy information retrieval of gird users is proposed. The algorithm improves the classical VSM model. Using Single-Dimension Semantic Vector Tuples of management node in Educational Resource Grid, the node calculate the overall semantic relevance of documents and retrieval vector directly, and carry on Top-k score combining with the document attributes of itself, which realized distributed full-text Top-k retrieval. It can also update Single-Dimension Semantic Vector Tuples by the feedback of retrieval results. It proposes a Top-k threshold strategy by a combination of semantic relevance of retrieval vector and node attributes, which can raise retrieval efficiency of distributed full-text Top-k retrieval on the premise of guarantying the validity of the retrieval.(6) The Educational Resource Grid Platform based on the environment of P2P Grids is designed and implemented. The platform is based on the SOA architecture, has friendly interface and easy operation. The features of platform include addition, modification, deletion, discovery and retrieval of resources, which achieve the integration and sharing of educational resources. The platform can find resource information which meets the requirements of clients from a large number of resource nodes, provides information retrieval services for educational resources, and achieve wide-area search and lactation of distributed resources. It also provides support functions including resource management (resource addition, deletion, modification, audition, etc.), node management and user management (user register, review, authorization, etc.).