The Research On Information Sharing Based On Peer-to-Peer Computing

Peer-to-Peer computing (P2P) is a new network model that has been sweeping through the computing industry over the past year or so. Being supported by distributed computing technology, P2P has several special features. In a P2P-based system, each peer has equal functionalities and responsibilities: each peer can act both as server to supply resource, and as client to utilize resource provided by other peers. Furthermore, the interaction among peers can be direct and symmetric without relying on the centralized server. In addition, peers can join in or leave from the system at any time to form dynamic network environment. Compared with the traditional Client/Server model, P2P has many advantages, such as scalability, self-organization, dynamicity, the elimination of bottleneck caused by centralized servers and the higher utilization of network resources. For these reasons, there is great potential to apply P2P technology for information sharing.This paper is devoted to the issues of information sharing in P2P environment. It studies system architecture, semantic information interaction, self-organizing network topology, and distributed search techniques for supporting information sharing in dynamic P2P environments with autonomic and large-scale distributed peers. Detailed research works have been done on the above issues. The main contributions are as follows:1. For the sake of effective resources organization, the system architecture, named REC, is proposed by combining the strength of traditional centralized network (ex. easy to manage) and distributed network (ex. good regional autonomy, load balance and robustness). REC endows high capability peers with more responsibilities to deal with the problem of peer capability heterogeneity, which enhances the performance of the network. REC differs itself from existing system architecture in that, its topology connections classification mechanism enables the topology construction according to peers'resources and query requirements, reflecting the altruism and selfish nature of peers and providing a foundation to effective resources organization and efficient search.2. The mechanism of semantic information interaction is studied. First, ontology-based resource metadata model, called MO, is proposed. Based on ontological descriptions of the metadata characterizing the resources to be shared, a semantic fuzzy matching algorithm, named SFM, is proposed by exploiting the linguistic and contextual characteristic of concepts. Through computing the semantic affinities between different ontological descriptions, and classifying the semantic association, resource fuzzy matching is supported, which gives the possibility for users to obtain more semantic-related data for decision-making. 3. Referring to the human society organization, a method of self-organizing P2P network based on interest is proposed. Based on the introduced dynamic topology model, called DTL, the P2P network is organized by clustering peers with similar interests into a community and choosing important communities as logical neighbors for individual peers in view of query requirement. The subsequently proposed self-organizing topology evolution algorithm, named SOTE, ensures that the connections between peers are dynamically reconfigured as peers'interests change. Therefore, the self-organization network topology can provide an efficient searching space from the viewpoint of each peer. The simulation result indicates SOTE can automatically optimize the network so that each peer can maintain near neighborship with peers with similar resources or provided resources. Also, the experiment proves that the employment of SOTE leads to adaptative as well as scalable P2P network construction technique.4. A self-adaptative distributed search technique, named SAS, is investigated. Existing searching mechanisms in unstructured P2P network are not scaling well because of the mechanism of peers randomly choosing logical neighbors without any knowledge about where to forward a query message, which greatly limits the performance gain from various search or routing techniques. Under the assumption of"peer maintaining near neighborship with peers in similar interests by virtue of topology evolution", SAS enables peers to select the most possible peers that have the answers to send queries, dynamically reflecting the change of resource distribution and requirement. Owing to the intelligent message forward technique based on content of request, the search request can quickly reach the destination peer, mostly nearby, which shortens the search path length, decreases response time, saves network bandwidth and improves the search recall. Simulation demonstrates that SAS can greatly improve the search efficiency and meanwhile guarantee the search effectiveness.