Information field theory of A. A. Denisov – 50 years

50 years ago, in 1974, A. A. Denisov proposed a theory based on a dialectical generalization of the laws of functioning and development of systems of various physical natures, which he called the theory of the information field. The theory is based on the use of the apparatus of mathematical field theory to explain the laws of information reflection, which determined its name. Based on this theory, significant results were obtained for the study of motion control processes in continuous spatio-temporal and arbitrarily evolving situations. The use of this theory for the study of open distributed information systems seems promising. Subsequently, a discrete version of the theory was developed, which allows explaining the process of reflection and transformation of information and became the basis for the development of a number of practical applications, some of which are given in this article. This article characterizes the prerequisites for the emergence of this theory, the main ideas and concepts of the theory and its contribution that, over the 50 years, scientists and students united by the Scientific and Pedagogical School “System Analysis in Engineering and Control”, have made on the basis of this theory in the development systems theory, computer science and other sciences of systems. Information is provided on the application of A. A. Denisov’s ideas and the development of models for specific applications based on them. The authors of the article, including Anatoly Alekseevich’s students, was developing, appliing and are currently developing models of information theory of A. A. Denisov, proving the usefulness of theoretical knowledge for solving practical problems.