Most of the operational information retrieval (IR) systems in existence today useBoolean logic during search. Such systems are usually called Boolean IR systems. These systems, as any other IR systems, are not perfect and the problem of their development (and hence providing better quality service for real users) is one of the most important problems in Information Science. From this viewpoint, the article analyzes existing criticisms of operational systems and points out some of their positive features. At the same time, certain negative effects which hinder the development of existing systems are considered. Finally, the article provides several conclusions about using Boolean logic in developing multiversion IR systems.

Most of the operational information retrieval (IR) systems in existence today use Boolean logic during search. Such systems are usually called Boolean IR systems. These systems, as any other IR systems, are not perfect and the problem of their development (and hence providing better quality service for real users) is one of the most important problems in Information Science. From this viewpoint, the article analyzes existing criticisms of operational systems and points out some of their positive features. At the same time, certain negative effects which hinder the development of existing systems are considered. Finally, the article provides several conclusions about using Boolean logic in developing multiversion IR systems.

This article initiates a study of multiversion information retrieval (IR) systems. The term "multiversion" refers to the existence of several different methods for realizing one (as a minimum) system's process. The article also provides a theoretical justification for the necessity of creating such systems to perform an optimal search for the satisfaction of the user's information need. The basic principles for designing multiversion IR systems are described.These principles are used in developing a method for selecting an optimal (the best of possible) state of the system for each individual user. We also indicate how the proposed method is used in conjunction with the feedback mechanism in the IR system. The results of an experiment illustrate the capabilities of multiversion systems and their advantages over traditional IR systems. It is shown that multiversion IR systems are superior in their abilities to adapt to an individual user in the process of satisfying user information need. 0 1993John Wiley 81 Sons, Inc.

The paper describes an approach to the design and implementation of an information retrieval (IR) system capable of providing an optimal search for each individual user. On the basis of the properties of information need, the paper analyzes the peculiarities of optimal search in documentary IR systems. The problems arising in implementing optimal search in such a system are considered and concrete solutions of some of these problems are proposed. In particular, the paper describes a simple and convenient method of selecting the 'best result' and proposes an algorithm for organizing optimal search in the systems realizing SDI (selective dissemination of information). This algorithm can be utilized, without substantial modifications, in many systems capable of using different search methods.

In the present work, a new approach to construction of single‐valued measures for evaluation of search results is considered in detail. This approach is based first on the formation of certain vectors, and second on the use of functions allowing the evaluation of their closeness. Realization of this approach leads to construction of new, as well as widely‐known, single‐valued measures. A series of constructed measures has a property important in practice, leading to the creation of a mechanism which would allow the selection of the best search method (from a set of available methods) for every query. In this article, a general statement of this property, called the order preservation property, is given, and all considered single‐valued measures are analyzed for the existence of this property. Finally, problems of the legitimacy of the use of single‐valued measures in various specific situations are discussed in the article, and an approach to the solution of these problems is suggested. © 1997 John Wiley & Sons, Inc.