Introducing Ranked Retrieval

Phrase Queries and Positional Indexes

Query Processing with the Inverted Index

The Inverted Index

Term Document Incidence Matrices

Introduction to Information Retrieval System

Information versus Data Retrieval

Data retrieval, in the context of an IR system, consists mainly of determining which documents of a collection contain the keywords in the user query which, most frequently, is not enough to satisfy the user information need. In fact, the user of an IR system is concerned re with retrieving information about a subject than with retrieving data which satisfies a given query. A data retrieval language aims at retrieving all objects which satisfy clearly defined conditions such as those in a regular expression or in a relational algebra expression Thus, for a data retrieval system, a single erronua object among a thousand retrieved objects means total failure.