Query Routing and Processing in Peer-To-Peer Data Sharing Systems

Sharing musical files via the Internet was the essential motivation of early P2P systems. Despite of thegreat success of the P2P file sharing systems, these systems support only "simple" queries. The focus in suchsystems is how to carry out an efficient query routing in order to find the nodes storing a desired file. Recently,several research works have been made to extend P2P systems to be able to share data having a fine granularity(i.e. atomic attribute) and to process queries written with a highly expressive language (i.e. SQL). These workshave led to the emergence of P2P data sharing systems that represent a new generation of P2P systems and, onthe other hand, a next stage in a long period of the database research area. The characteristics of P2P systems (e.g. large-scale, node autonomy and instability) make impracticalto have a global catalog that represents often an essential component in traditional database systems. Usually,such a catalog stores information about data, schemas and data sources. Query routing and processing are twoproblems affected by the absence of a global catalog. Locating relevant data sources and generating a close tooptimal execution plan become more difficult. In this paper, we concentrate our study on proposed solutions forthe both problems. Furthermore, selected case studies of main P2P data sharing systems are analyzed andcompared.