Introduction to Information Retrieval and Web Search

Chapter 27

Introduction to Information Retrieval and Web Search

_In most of the chapters in this book so far, we have dis-cussed techniques for modeling, designing, querying, transaction processing of, and managing structured data. In Section 12.1 we dis cussed the difference between structured, semistructured, and unstructured data. Information retrieval deals mainly with unstructured data, and the techniques for indexing, searching, and retrieving information from large collections of unstructured documents. In this chapter we will provide an introduction to information retrieval. This is a very broad topic, so we will focus on the similarities and differences between information retrieval and database technologies, and on the indexing techniques that form the basis of many information retrieval systems.

This chapter is organized as follows. In Section 27.1 we introduce information retrieval (IR) concepts and discuss how IR differs from traditional databases. Section 27.2 is devoted to a discussion of retrieval models, which form the basis for IR search. Section 27.3 covers different types of queries in IR systems. Section 27.4 discusses text preprocessing, and Section 27.5 provides an overview of IR indexing, which is at the heart of any IR system. In Section 27.6 we describe the various evaluation metrics for IR systems performance. Section 27.7 details Web analysis and its relationship to information retrieval, and Section 27.8 briefly introduces the current trends in IR. Section 27.9 summarizes the chapter. For a limited overview of IR, we suggest that students read Sections 27.1 through 27.6.