Information Retrieval

Information retrieval (IR) is a set of techniques that extract from a collection of documents those that are relevant to a given query. Initially addressing the needs of librarians and specialists, the field hasevolved dramatically with the advent of the World Wide Web. It is moregeneral than data retrieval, whose purpose is to determine which documentscontain occurrences of the keywords that make up a query. Whereas thesyntax and semantics of data retrieval frameworks is strictly defined, withqueries expressed in a totally formalized language, words from a naturallanguage given no or limited structure are the medium of communication forinformation retrieval frameworks. A crucial task for an IR system is to indexthe collection of documents to make their contents efficiently accessible.The documents retrieved by the system are usually ranked by expectedrelevance, and the user who examines some of them might be able toprovide feedback so that the query can be reformulated and the...