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. © 1993 John Wiley & Sons, Inc.

Abstract Shortest path algorithms for graphs have been widely studied and are of great practical utility. For the case of a general graph, Dijkstra's algorithm is known to be optimal. However, in many practical instances, there is a “level” structure which may be imposed on the underlying graph. Utilizing these levels, this paper demonstrates that the time complexity of shortest path generation may be greatly reduced. A new graph structure, the level graph, together with a simple uniformed heuristic, LGS, for searching that structure is introduced, which allows for rapid generation of approximate shortest paths. LGS is studied both analytically and via simulation. It is shown that the length of the path produced by LGS converges rapidly to that of the actual shortest path as the distance between the points increases.

On the basis of several pragmatic assumptions we developed an algorithm for the automatic construction of query formulations in Boolean form. The suggested algorithm also substantially simplifies the end-user interaction. The user expresses his search request by a set of documents pertinent to his need. The quality of the search depends only on the algorithm and on how completely and precisely the information need of a user is represented in his search request. The algorithm might also be useful for correcting query formulations on the basis of the user's feedback during his interaction with the system. © 1991 John Wiley & Sons, Inc.

This article addresses the problem of control in documentary information retrieval systems. The nature of control in IR systems is analyzed and it is shown why an IR system has to be looked at as an adaptive system. The mechanism of feedback realizing system's adaptation to the user is described. The algorithms of feedback are proposed and it is shown how they depend on the type of the collection of documents: static (no change in the collection between searches) and dynamic (when the change occurs between searches). The proposed algorithms are the basis for the development of the fully automated information retrieval systems. © 1991 John Wiley & Sons, Inc.