Introduction

Abstract

Intelligent query processing allows users to query a global information system without being aware of the site, structure, query language, and semantics of the data repositories that store the relevant data for a given query. Three main aspects of intelligent query processing are considered in this book. First, metadata can capture the information content of the repositories. The user queries the global information system by expressing information needs using intensional metadata descriptions. So the user can pose a query by specifying what she or he wants to know, and the system should determine where the information can be found and present the answer to the user. Second, mappings exist among the intensional descriptions and the underlying data repositories. These mappings play a key role in encapsulating the heterogeneity due to the different formats and data organization in the various repositories. Third, difficulties are encountered in query processing in open and dynamic environments, defining strategies that permit an efficient retrieval of relevant data when the number of data repositories available is huge, and dealing with the different semantics associated with each data repository.