P2P环境下数据管理系统上的Top-k查询

目前大多数P2P系统只提供文件的共享,缺乏数据管理能力.基于关系数据库上的关键搜索,本文提出了一种在P2P环境下共享数据库的新框架,其中每个节点上的数据库被看成是一个文档集,用户不用考虑数据库的模式结构信念,简化了不同节点数据库模式间的映射过程,能更好地适应P2P的分散和动态特性.将基于直方图的分层Top-k查询算法扩展到P2P环境下的数据库管理系统上,文档集和数据库的查询被统一起来,一致对待.在查询处理期间,直方图可以自动更新,同时根据查询结果,邻居节点可以自调整,具有自适应性.实验结果表明,基于关键词的数据库共享突破了传统的数据库共享模式,简化了数据访问方式,而基于直方图的Top-k查询算法提高了查询效率.

Top-k Query over Data Management System in P2P Network

Most of existing peer-to-peer (P2P)systems only provide coarsely granular file-level sharing and lack of data management ability. A new framework of database sharing in P2P network is presented, which is based on keyword search over relational databases. In the framework, database on each peer can be seen as a text collection, users needn' t care about the schema information of the database, which greatly simplifies the schema mapping between different peers, and is more suitable for the decentralization and dynamicity of P2P network. Hierarchical top-k query processing algorithm based on histogram is applied in the data management system in P2P network to do top-k query, which uni- fies the query over text collections and relational databases. During the query processing, histogram can be updated au- tomatically by using the returned top-k results, and the neighborhood of the peer can be self reconfigured to let the nodes containing the real top-k results to be its neighbors. Experiment results show that database sharing based on the keyword searching breaks through the traditional database sharing schema and simplifies the data accessing method, and top-k query based on histogram improves the search efficiency.