AN EVALUATION OF RETRIEVAL EFFECTIVENESS FOR A FULL-TEXT DOCulwvT-l?ETl?lEviiL SYSTEM

Document retrieval is the problem of finding stored documents that contain useful information. There exist a set of documents on a range of topics, written by different authors, at different times, and at varying levels of depth, detail, clarity, and precision, and a set of individuals who, at different times and for different reasons, search for recorded information that may be contained in some of the documents in this set. In each instance in which an individual seeks information, he or she will find some documents of the set useful and other documents not useful; the documents found useful are, we say, relevant; the others, not relevant. How should a collection of documents be organized so that a person can find all and only the relevant items? One answer is automatic full-text retrieval, which on its surface is disarmingly simple: Store the full text of all documents in the collection on a computer so that every character of every word in every sentence of every document can be located by the machine. Then, when a person wants information from that stored collection, the computer is instructed to search for all documents containing certain specified words and word combinations, which the user has specified. Two elements make the idea of automatic full-text retrieval even more attractive. On the one hand, digital technology continues to provide computers that are larger, faster, cheaper, more reliable, and easier to use; and, on the other hand, full-text retrieval avoids the