Synopsis Information retrieval (IR) is the art and science of searching for information in documents, searching for documents themselves, searching for metadata which describes documents, or searching within databases, whether relational stand alone databases or hypertext networked databases such as the Internet or intranets, for text, sound, images or data. IR is a broad interdisciplinary field, that draws on many other disciplines. Indeed, because it is so broad, it is normally poorly understood, being approached typically from only one perspective or another. The present volume describes how an information retrieval system really works. Its contents and organization has been carefully designed to present a cohesive view of all the important aspects of modern information retrieval. The book is intended for students of library is intended for students of library and information science, but it may well be of interest to practitioners working on commercial information retrieval systems as well as people who are faced with problems in selecting an information retrieval system.