Uhrynovskyi B. Methods and tools of software reliability improvement considering software aging

The dissertation solves a topical scientific and applied problem in the field of software engineering - increasing the software reliability for mobile systems by identifying factors influencing the aging process, building software aging and rejuvenation mathematical models and developing appropriate tools. The dissertation consists of an introduction, four chapters, conclusions, a list of references and appendices. The introduction substantiates the relevance of the topic of dissertation research; describes the connection of work with scientific programs, plans, topics; the purpose and main tasks of the dissertation are formulated; research methods are presented and scientific novelty is determined and the practical significance of the obtained research results is reflected; lists of published works on the topic of dissertation work and conferences were presented, at which the main results of the dissertation work were tested. The first chapter discusses the concept of software aging and key characteristics such as defects, errors, effects, metrics and aging factors. It is determined that the phenomenon of aging has a significant negative impact on the software reliability and performance. Various methods of research and modeling of the software aging phenomenon are considered and analyzed. The importance of empirical and theoretical research of the aging process and methods of counteracting its effects in mobile operating systems, in particular, Android, is justified, because mobile and embedded devices are vulnerable to the effects of aging, and their daily use requires a high level of reliability. The actual scientific and applied problems that will be solved in this work are formulated. The second chapter analyzes the existing model of software aging and rejuvenation for the Android operating system considering the usage activity of mobile device, identifies the main disadvantages of this model and offers improved models of aging and rejuvenation, which take into account both user activity and mechanisms of warm and cold rejuvenation, different aging levels and possible rejuvenation strategies, as well as the battery charge factor. The third chapter presents the results of experimental studies of the software aging phenomenon in the Android operating system, in particular, the analysis of metrics and aging factors. Two new graphical user interface metrics have been proposed and experimentally tested in the context of software aging: frame draw time and junky frames count. New aging factors have been explored, namely cross-platform applications based on the Flutter framework and the scenario of using a mobile device with pauses when generating workload. Based on the performed theoretical and practical research, the software rejuvenation method for the Android operating system is proposed and described. The fourth chapter describes the general methodology for researching software aging in the Android operating system, which is used in this paper to study the metrics, factors, and features of aging processes. A framework has been developed to perform stress testing of Android mobile applications and perform analysis of collected data in accordance with a predefined research methodology. The structure of software modules for the Android operating system has been developed, in the context of which it is possible to implement the software rejuvenation method proposed in the third chapter.