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The purpose of this paper is to provide the general method for the solution of the Boolean function's primary function, and its application in encryption systems.

In the Boolean function theory, there is always a lack in the general method for the solution of primary function. This paper uses a very useful tool – e‐derivative, and by the help of this tool, obtains some very useful theorems.

The paper not only finds the method of solving the primary function of the Boolean function but also provides its application in encryption systems.

The Boolean function's primary function is also very useful in the detection of circuitry, not introduced in this paper.

This paper is very useful for information security.

The paper solves the initial‐value problem of the Boolean function's primary function, and constructs some Boolean functions with many cryptographical characters which are very useful in encryption systems.

A new and promising approach to document clustering consists of utilizing previously formed clusters of queries to cluster documents. To employ this approach in practice a similarity measure for queries must be available. This requirement does not cause any problem in the case of information retrieval systems in which both the search request formulations and document representations are sets of weighted or unweighted index terms. However, in most operational retrieval systems search request formulations are Boolean combinations of index terms. Research into similarity measures for search request formulations of this type has already been undertaken by the author and reported elsewhere. The present paper provides further results of investigations in this area. The novelty of the approach discussed is the incorporation within the methodology described earlier of a weighting mechanism to indicate the relative importance of particular attributes of a given Boolean search request formulation. A modification suggested is based on the standard probabilistic approach to information retrieval.

A need for developing an information retrieval technique maintaining the appeal of Boolean retrieval schemes and in addition providing the advantages of a ranked search output has been pointed out in the literature for many years. However, a previous attempt to incorporate into the Boolean retrieval schemes a weighting mechanism to produce ranked lists of documents has not been fully successful. Specifically, further research has demonstrated that the theory behind the previous approach is characterized by disturbing ambiguities and inconsistencies, with equivalent Boolean search request formulations yielding different rankings of documents retrieved. As a result of this more recent research an alternative approach has been outlined. However, a closer analysis of this second approach reveals that it is also not free from some intrinsic weaknesses. The present paper provides the results of this new analysis and suggests a more rigorous methodology.

Characterizes the well known set‐representation of fuzzy sets (Négotia‐Ralescu), as a P(X)‐valued Boolean, Dedekind cut, and at the same time generalizes it to general Boolean algebras. Uses the theory of Boolean powers and Boolean‐valued Dedekind cuts.

One technique for searching a Co‐ordinate Index is to compare each reference with a Boolean expression of index terms. This divides the file into retrieved and not‐retrieved references. An alternative is to assign each reference a score calculated from its index terms and to retrieve the N highest scoring references in the file. This scoring technique has several advantages in theory, and it performed slightly better in a retrieval test with N equal to the number of references retrieved by the corresponding Boolean search. In the test a minimum value of N = 10 was used, and when less than this number of references matched the Boolean search requirement, the Scoring technique successfully widened the scope of the search and retrieved twice as many relevant references as the Boolean searches.

There have been several document ranking methods to calculate the conceptual distance or closeness between a Boolean query and a document. Though they provide good retrieval effectiveness in many cases, they do not support effective weighting schemes for queries and documents and also have several problems resulting from inappropriate evaluation of Boolean operators. We propose a new method called Knowledge‐Based Extended Boolean Model (kb‐ebm) in which Salton's extended Boolean model is incorporated. kb‐ebm evaluates weighted queries and documents effectively, and avoids the problems of the previous methods. kb‐ebm provides high quality document rankings by using term dependence information from is‐a hierarchies The performance experiments show that the proposed method closely simulates human behaviour.

A relevancy‐ranking algorithm for a natural language interface to Boolean online public access catalogs (OPACs) was formulated and compared with that currently used in a knowledge‐based search interface called the E‐Referencer, being developed by the authors. The algorithm makes use of seven well‐known ranking criteria: breadth of match, section weighting, proximity of query words, variant word forms (stemming), document frequency, term frequency and document length. The algorithm converts a natural language query into a series of increasingly broader Boolean search statements. In a small experiment with ten subjects in which the algorithm was simulated by hand, the algorithm obtained good results with a mean overall precision of 0.42 and mean average precision of 0.62, representing a 27 percent improvement in precision and 41 percent improvement in average precision compared to the E‐Referencer. The usefulness of each step in the algorithm was analyzed and suggestions are made for improving the algorithm.

The user interface, in broad terms, is the medium through which the user and the information come together. The types of searches a public access catalog (PAC) can perform are defined by the indexing strategy and retrieval software. The way the user's interest is communicated to the retrieval software and the way the results are communicated to the user is, by a more narrow definition, the interface software. Both the kinds of searches that can be performed by a variety of CD‐ROM PACs and how their workstations are used to accomplish the searches are considered.

This paper reports the results of a study funded by the Arts and Humanities Research Board which sought to investigate links between Web search strategies and retrieval effectiveness. A total of 68 students, enrolled on masters programmes in librarianship, information management and information systems, searched for two topics using the AltaVista search engine. Logs of the resultant 341 queries, along with relevance judgements for over 4,000 retrieved items, were analysed using factor analysis and regression. The differing but complementary types and strengths of evidence produced by these two forms of analysis are discussed and presented. Retrieval effectiveness was associated positively with best‐match searching and negatively with Boolean searching. The implications of these findings for Web searching are discussed.

Although the Boolean combination of keywords and/or subject codes is the predominant access method for the retrieval of passages from full‐text databases, menu access is an attractive alternative. The selection of an access method and the ensuing satisfaction with the results is based on the type of query and on the experience and knowledge of the user. This paper describes a prototype system which has integrated Boolean, menu, and direct access methods for the retrieval of passages from full‐text databases. The integration is based on the hierarchical structure inherent in such databases as legal statutes and regulations and engineering standards. The user may switch freely among access methods in order to develop the most appropriate search strategy. The retrieved passages are presented to the user within the context of the hierarchical structure.