This book provides a theoretical and practical explanation of the latest advancements in information retrieval and their application to existing systems. It takes a system approach, discussing all aspects of an Information Retrieval System. The major difference between this book and the first edition is the addition to this text of descriptions of the automated indexing of multimedia documents, as items in information retrieval are now considered to be a combination of text along with graphics, audio, image and video data types. The growth of the Internet and the availability of enormous volumes of data in digital form have necessitated intense interest in techniques to assist the user in locating data. The importance of the Internet and its associated hypertext linked structure are put into perspective as a new type of information retrieval data structure. The total system approach also includes discussion of the human interface and the importance of information visualization for identification of relevant information. With the availability of large quantities of multi-media on the Internet (audio, video, images), Information Retrieval Systems need to address multi-modal retrieval. The primary use of this book is as a college text on Information Retrieval Systems. But in addition to the theoretical aspects, the book maintains a theme of practicality that puts into perspective the importance and utilization of the theory in systems that are being used by anyone on the Internet. The student will gain an understanding of what is achievable using existing technologies and deficient areas that warrant additional research. The text provides coverage of all of the major aspects of information retrieval and has sufficient detail to allow students to implement a simple Information Retrieval System.