XML Query Routing in Structured P2P Systems

Abstract

This paper addresses the problem of data placement, indexing, and querying large XML data repositories distributed over an existing P2P service infrastructure. Our architecture scales gracefully to the network and data sizes, is fully distributed, fault tolerant and self-organizing, and handles complex queries efficiently, even those queries that use full-text search. Our framework for indexing distributed XML data is based on both meta-data information and textual content. We introduce a novel data synopsis structure to summarize text that correlates textual with positional information and increases query routing precision. Our processing framework maps an XML query with full-text search into a distributed program that migrates from peer to peer, collecting relevant document locations along the way. In addition, we introduce methods to handle network updates, such as node arrivals, departures, and failures. Finally, we report on a prototype implementation, which is used to validate the accuracy of our data synopses and to analyze the various costs involved in indexing XML data and answering queries.