Current P2P data sharing systems process queries issued by peers with data granularity of files. However,these methods cannot implement advanced query processing on finer granularity datasets, such as relational data, XML etc. In this paper, we propose a P2P view-based query processing framework on relational datasets: (1)peers issued the same query (or subquery) build views through collaborative scheme; (2)peers then answer queries directly from these views. It is proved that the view-based query processing in P2P environment can greatly reduce the bandwidth consumption on eacb. peer, and greatly improve the response time of queries.

GML是由OGC推出的一种基于XML数据格式的地理标记语言，是空间数据编码、传输、存储和发布的一种国际标准，适用于Internet环境中的地理数据共享、交换和集成。随着GML的广泛应用，如何有效地管理GML数据是亟待解决的问题。提出了一种基于模型映射的GML文档存储和查询方法，该方法主要针对无模式的GML文档，也可用于有模式GML文档的存储。通过对文档树结点的分析和处理，建立文档到对象关系数据库模式的映射，保留文档中的结构信息，实现GML文档到数据库中的存储；并支持空间数据分析和非空间信息查询。

Query processing in P2P environment is gaining more and more attention in database research community, and most of the P2P-based query processing systems only consider the processing strategies. However, estimating the cost of query processing is crucial to clarify which factors will affect the efficiency of query processing, and how to optimize the query processing. In this paper, a model is proposed to estimate the cost for query processing in P2P systems. Methods in the model do not depend on the global information in the network, and they only need a small quantity of data transferring to complete the estimation. Experimems are presented to evaluate the efficiency and the effectiveness of the estimation methods.

In this paper,a self-adaptive query routing strategy is introduced for resource location in F2P environment. Each peer builds up query routing table based on contribution on each query topic from its neighbors, guides efficient and effective routing hints for similar queries, and improves traditional query routing strategies based on DFS and BFS in P2P systems.

Query processing is a crucial problem for the success of data management in P2P systems. In this paper, a multi-phase and distributed view selection strategy is introduced. It is proved that in P2P environment view selection can boost query processing efficiency and effectiveness.