Aim. The paper continues the series of publications that investigate and discuss the essence and definitions of the basic concepts of the dependability theory. It analyzes the basic concept, which is the subject of consideration in dependability, for which the term “item” is usually used. The concept of “dependability” is defined for it, and in general all the terminology of dependability applies to it. The following issues are considered: how to name and define this subject of consideration, what it can be, what can be its constituents. In particular, the relationship between the concepts of “item” and “product” is discussed.

Methods. The evolution of definitions of this concept in the Russian and international terminological standards in dependability over the past 30 years is traced. A comparative analysis of other standards and federal laws relating to items of different types is carried out. The viability of two main ways of getting an idea of a concept is considered: illustrative (based on examples) and definitional (by means of sequential definition of some concepts through others).

Findings and conclusions. The definition and correct understanding of the concept of “item” is of great importance, as it affects the scope of dependability standards. It is explained why it is necessary to accept that the definitions of the basic concepts cannot be rigorously formalized and are in fact only explanations. It is shown that the definitions of the item in the existing Russian and international standards (GOST 27.002–2015 and IEC 60050-192:2015) have inaccuracies. To eliminate them, improved notes to the definition of an item are proposed. The first note lists the possible types of items: products (parts, assembly units, complexes) and their components; buildings and structures; systems consisting of jointly functioning products and structures and their subsystems. The second note indicates the relationship between the main constituents of the item: hardware, software and people (personnel), and their possible combinations. The paper provides reasons for considering virtual items that play an important role in today’s information and telecommunication technologies and are logically isolated subsystems within the systems that they are part of. Besides that, it points out the deficiencies in the definitions of various items in GOST 18322–2016.

The Aim of the paper is to develop an algorithm of prompt detection of the moment of dependability characteristics variation in a system that consists of a set of homogeneous elements, assuming that failures of such elements occur at random moments in time, are a Poisson flow of events and, consequently, the time intervals between them are an exponential probability distribution. In order to solve the problem, it is suggested using one of the classical algorithms of detection of “imbalance” of a discrete random process, i.e. spontaneous change of one of its probabilistic characteristics. As such a characteristic, the exponential distribution parameter θ was chosen, that is uniquely associated with the mean time between failures Тmn: θ = 1/Тmn. It is believed that the imbalance consists in the discontinuous variation of parameter θ from the initial steady state θ = θ0 to the level of minimal (expected, maximum allowable, critical) imbalance, when θ = θ1 > θ0. In this paper, the imbalance is detected using the cumulative sum algorithm (CUSUM) as it has certain optimal properties and is widely used in practice. For this algorithm, the required design ratios, descriptions of its properties and features are provided. The paper proposes a procedure for synthesizing the control algorithm with desired properties, in the course of which, based on the user-selected values of desired mean time between false alarms , initial basic level θ0 and nominal imbalance θ1 > θ0, the value of decision boundary Н is identified, the speed of algorithm action is estimated trough the calculation of the average lag in the detection of nominal imbalance , along with its efficiency for various values of d, that quantitatively characterize the value of imbalance: d=θ1/ θ0. For the purpose of practical implementation of the synthesis procedure, the paper cites reference data, that was obtained by means of simulation and that ensures the development of the control algorithm with required characteristics. It is noted that the presented synthesis procedure can, in principle, also be used for cases of gradual (continuous) change of parameter θ. However, the statistical properties of the control procedure will remain unclear as they require sufficiently intense additional research.

Optimal organization of the restoration process is of significant importance in the operation of technical, information and computer systems, since failures occurring during their operation lead to substantial negative consequences. In this paper, a formula for the variance of the number of failures is obtained for the general restoration process, which depends on the restoration functions (average number of failures) of the simple and general restoration processes. Also obtained are the formulas for the variances of the number of failures and restorations during the alternating restoration process, when along with the element’s time to failure, for example, the restoration time is taken into account. For an exponential distribution with a simple and general restoration process, formulas are written for the variance of the number of failures, as well as the Chebyshev inequality and the formula for the coefficient of variation of the number of failures for a simple restoration process. The paper presents an algorithm for obtaining dispersion in the form of series for the operation time distribution laws common to the dependability theory. The developed mathematics are intended for the definition and solution of various optimization problems of information and computer security, as well as in the operation of technical and information systems, software and formware information protection facilities affected by random failures, threats of attacks and security threats.

Aim. The results of evaluation of a technical system’s (facility’s) factual state allow making a decision on a further life (operation continuation, maintenance assignment, decommissioning and a facility’s replacement etc.). Under the conditions of resource limits, it is vital to identify most “problematic” facilities that require primary investments. The aim of the research is to develop a method of normalization of dependability indicators whose application is intended to improve targeted investment allocation for maintenance of facilities, which allows fulfilling the requirement of uninterruptible transportation under the conditions of resource scarcity.

Methods. The research uses methods of system analysis, probability theory, mathematical statistics, and correlation analysis. It proposes approximation of a time series of factual values related to a dependability indicator by a three-parameter gamma distribution based on a scarcity function q(x).

Findings. The research has considered the criteria of choice of railway transport facilities requiring the enhancement of dependability for the cases of unavailability and availability of a normalized dependability indicator. It has been shown that if introducing normalization of indicators one should take into account non-similar maintenance conditions for facilities in different enterprise units, which are determined by differences in climatic factors, technical capabilities for maintenance and repair, staffing levels, grades of tear and wear of facilities, requirements for their productivity. The research has analyzed the conditions of association of a service supplier’s and user’s requirements for normalization of a dependability indicator value. It has been demonstrated that it is reasonable to establish a single threshold normalized value xη of a dependability indicator, in which case a normalized value xη for the attribute x shall comply with the requirements of a service user as well as a service supplier. In the case of a single threshold value, the risk Qη = P{x > xη} of noncompliance of an indicator with the specified requirements is in fact split between a service user and a service supplier according to their agreement.

Conclusions. The paper proposes a method of normalization of a dependability indicator based on statistical data assuming that in general this indicator may be evaluated for a certain period of observance as acceptable for a service user. For to choose and justify the normalized value of a dependability indicator, the authors have studied the relations between a service supplier and a service user, have analyzed statistics using the method of estimation of empirical sufficiency of a raw data series as well as approximation of an ordered initial series by a three-parameter gamma distribution. The paper provides an example of normalizing a value of a facility failure rate indicator as per the criterion of a specified risk of its violation based on the quantiles of an obtained function of sufficiency. It has been shown that the proposed approach allows establishing a correlation between a normalized value and a risk of its violation via a function of sufficiency, which can be obtained on the basis of existing statistical data on a facility’s dependability for the past periods. This correlation makes it possible to guarantee the ensuring of compliance of factual and normalized indicator values with a specified risk level for a facility working in normal mode

Aim. Dependability simulation of a complex system starts with its structuring, i.e. partitioning into components (blocks, units, elements), for which probabilities of failure are known. The classical dependability theory uses the concept of structural function that allows ranking elements by their importance, which is required for optimal distribution of the resources allocated to ensuring system dependability. Man-machine systems are structured using an algorithmic description of discrete processes of operation, where the presence of clear boundaries between individual operations allows collecting statistical data on the probabilities of error that is required for modeling. Algorithmization is complicated in case of man-machine systems with continuous human activity, where the absence of clear boundaries between operations prevents the correct assessment of the probability of their correct performance. For that reason, the process of operation has to be considered as a single operation, whose correct performance depends on heterogeneous and interconnected human-machine system-related, technical, software-specific, managerial and other factors. The simulated system becomes a “black box” with unknown structure (output is dependability, inputs are contributing factors), while the problem of element ranking typical to the dependability theory comes down to the problem of factor ranking. Regression analysis is one of the most popular means of multifactor dependability simulation of man-machine systems. It requires a large quantity of experimental data and is not compatible with qualitative factors that are measured by expert methods. The “if – then” fuzzy rule is a convenient tool for expert information processing. However, regression analysis and fuzzy rules have a common limitation: they require independent input variables, i.e. contributing factors. Fuzzy cognitive maps do not have this restriction. They are a new simulation tool that is not yet widely used in the dependability theory. The Aim of the paper is to raise awareness of dependability simulation with fuzzy cognitive maps.

Method. It is proposed – based on the theory of fuzzy cognitive maps – to rank factors that affect system dependability. The method is based on the formalization of causal relationships between the contributing factors and the dependability in the form of a fuzzy cognitive map, i.e. directed graph, whose node correspond to the system’s dependability and contributing factors, while the weighted edges indicate the magnitude of the factors’ effect on each other and the system’s dependability. The rank of a factor is defined as an equivalent of the element’s importance index per Birnbaum, which, in the probabilistic dependability theory is calculated based on the structure function.

Results. Models and algorithms are proposed for calculation of the importance indexes of single factors and respective effects that affect system dependability represented with a fuzzy cognitive map. The method is exemplified by the dependability and safety of an automobile in the “driver-automobile-road” system subject to the driver’s qualification, traffic situation, unit costs of operation, operating conditions, maintenance scheduling, quality of maintenance and repair, quality of automobile design, quality of operational materials and spare parts, as well as storage conditions.

Conclusions. The advantages of the method include: a) use of available expert information with no collection and processing statistical data; b) capability to take into account any quantitative and qualitative factors associated with people, technology, software, quality of service, operating conditions, etc.; c) ease of expansion of the number of considered factors through the introduction of additional nodes and edges of the cognitive map graph. The method can be applied to complex systems with fuzzy structures, whose dependability strongly depends on interrelated factors that are measured by means of expert methods.

The Aim of the paper is to show the advantages associated with the application of the Toyota A3 Report as a standard method of information exchange. It must be noted that as of today this method has not found widespread application. It deserves better. Using specific examples of accidents involving mining machines, the authors show how a Report is completed hoping that this information will help in the adoption of this system in other enterprises. That may contribute to the solution of many problems of industrial management. This paper will be most useful for operators of mining machines.

The Method consists in presenting material on an А3 sheet of paper, that is required in order to set forth all the information needed to solve a problem. Why the А3 format? A3 is the maximum size of a sheet of paper that can be faxed. Before the emergence of personal computers it was the most common tool of communication between Toyota Motor factories. The above example of application of the Toyota A3 Report contains such crucial sections as maintenance and reliability of mining machines, information on prior research, application of the “5 Why?” method and consideration of the human factor. In the example given in the paper, the report describes the circumstances of the accident involving the SRs 1200 24/4 (G2) excavator, that occurred on April 6, 1995 in the open-pit mine Field D, mining basin Kolubara by the Electric Power Industry of Serbia. The report also includes an estimate of the consequences and analysis of the causes of the accident.

The Findings include the methodological approach to the solution of problems, brief format of information presentation, documentation and registration, so that other people involved in the process can review it; assuring the persons involved can form an idea of the operating procedures and outcome of problem resolution. A common language is provided for communication within the company along with a culture of Lean production. The А3 Report is a training process and foundation for future changes in the manufacturing process management.

Conclusions. The Toyota A3 Report has two primary functions: submission of proposals and reporting on the approved measures per the submitted proposals. It allows strictly defining the problem and proceeding to the measures aimed at improving the situation. The practical application of the Report as part of communication within the company and with suppliers will enable quick and targeted solution of managerial problems. Initially developed in Japan within the Toyota company, the method currently finds wider application in Serbian enterprises and elsewhere.

Aim. In the general case, a risk-oriented approach encompasses probabilistic methods of emergency processes and events simulation as well as deterministic methods. The use of probabilistic and deterministic estimations has been the focus of research aiming to improve safety and operational procedures. However, the experience of using probabilistic analysis only (essentially, one-criterium tool) has shown that this approach does not encompass all the required aspects of safety. The aim of the paper is to introduce (update) the definitions of the very concepts of “analysis” and “synthesis” as regards the risks for the purpose of research of safety of structurally complex systems (SCS) and design of systems for monitoring hazards and threats to their stable development thereof.

Method. The paper examines – from the point of view of systems science – the method of analysis and synthesis of risks as a development tool of advanced systems for monitoring SCS safety threats. The paper compares the primary current concepts of risk management in SCS and has shown that they should be developed and improved. A type of risk functionality is proposed that allows defining a safety solution by the value of mathematical expectation of losses, with appropriate corrections taken into account.

Result. The concept of “risks synthesis” is introduced as a scientific tool integrated with analysis that takes into consideration the existing connections between the elements of considered SCS in terms of a whole system in its entirety. Principles are formulated for the collection of comprehensive sets of data required for decision-making.

Conclusion. The proposed approach paves the way for the development of the method of risks synthesis and suggests the development of advanced expert systems to support decision-making regarding the safety of SCS as multifunctional and multilevel systems intended for both recording and analysis of each individual case (event), and prediction of trends and preparation of prevention measures as necessary.

Aim.The digital transformation of the traffic safety management system in JSC RZD involves top-level integration with the operating processes of all business units in terms of integral assessment of the risk of possible events and achievement of specified indicators. The result will be the merger of the traffic safety management system with the processes of all levels of the company’s management enabled by an integrated intelligent system for managing processes and services whose functionality includes real-time traffic safety management.

Methods. The paper uses system analysis of existing approaches and methods of processing of large quantities of structured and unstructered data.

Results. The paper examines the development stages of train traffic safety management, as well as automated information and control systems that enable traffic safety management. General trends in the creation of systems for collection and processing of information are analyzed. The applicability of such technologies as Big Data, Data Mining, Data Science as part of advanced control systems is shown. The paper examines the performance of the above technologies by analyzing the effect of various factors on the average daily performance of a locomotive, where, at the first level, such factors as average daily run of a locomotive, average trainload are taken into consideration; at the second level, the focus is on the service speed, locomotive turnover at station, etc.; at the sixth level, the focus is on the type of locomotive, its technical state, etc. It is shown that statistical methods of factor analysis and link analysis combined with such other methods of Data Mining as methods of simulation and prediction, the average daily performance of a locomotive can be planned proactively. The author proposes a procedure of migration towards a digital traffic safety management system that would be based on models of interaction of safety and dependability factors of all railway facilities at all railway levels of hierarchy, as well as in association with other factors that have no direct relation to dependability, yet affect the safety of the transportation process.

Conclusions. The primary benefit of migration towards Big Data consists in the development of a dynamic model of traffic safety, the elimination of human factor in control systems. Most importantly, it enables the creation within the Russian Railways company (JSC RZD) of an integrated intelligent process and service management system that enables real-time traffic safety management. An extensive process of development and deployment within the company of the URRAN Single Corporate Platform (SCP) enabled executive decision support as regards risk-based functional dependability and safety of transportation facilities. Thus, the URRAN SCP sets the stage for the digital transformation of the traffic safety management system in JSC RZD.