Dependability Assurance Research Articles

Method for designing and developing space mechanisms with specified dependability

Aim. According to the established concept of space launch, practically each of the spacecraft in a near-Earth orbit needs to separate from the launch vehicle and deploy its folded structures (solar panels, antennas, reflectors, rods, etc.) in the operational position and only then is able to become fully functional for its intended purpose. The reliability requirements for single-operation mechanisms are so high, that any unidentified potential threat of critical failure in the course of design, development, manufacture and operation may make the creation of such spacecraft pointless, which is confirmed by the fatal results of the missions of the Sinosat- 2, Ekspress-АМ4, Kanopus-ST, Zuma, Chinasat-18 and many other satellites and space objects. The design of space mechanisms with a specified dependability is complicated by the fact that practically all of them are unique, highly critical systems that are supposed to be as reliable as possible, are unique or rare in terms of their design, are manufactured at most in small series and operate in unique environments. Statistical data on the dependability of components and elements of mechanisms that operate in the open space environment is at best insufficient for obtaining reliable dependability calculation results using the statistical methods of the modern dependability theory, while at worst they do not exist at all. In the context of constantly growing complexity of space technology and increasing costs of any in-orbit failure there is an objective necessity for developing a method for designing space mechanisms based on the evaluation of the specified dependability using the engineering solutions (without involving statistical methods of dependability) and early failure prevention procedures. Methods. The paper presents a method for designing and developing space mechanisms based on the design engineering analysis of dependability. Results. The method proposed in the paper allows modifying the analytical verification toolkit, thus migrating from design and expert methods (e.g., Stage-Gate or FMEA) of product design to purely engineering ones that are based on engineering disciplines and design engineering methods of ensuring quality and dependability. The use of design engineering analysis of dependability as part of the design and development enables dependability assurance as a natural and integral part of a designer’s work that enables engineering decision-making in accordance with the specified dependability requirements (rather than in an isolated manner).

Design engineering approach to ensuring specified dependability. Case study of unique, highly critical systems with short operation life

Aim. To examine the design engineering approach to ensuring specified dependability on the basis of engineering disciplines and design engineering methods of quality and dependability assurance using the case of unique, highly critical products with short operation life. Such approach, unlike the statistical procedures of modern dependability, allows associating the dependability indicator calculations with the calculated operability parameters and established design criteria that are to be met in order to confirm the specified dependability indicators for products with an indefinite number of critical elements, each of which operates according to a functional principle that is different in its nature. Methods. The paper examined the prerequisites for the implementation of the design engineering approach to dependability, such as the distinctive features of ensuring the dependability of unique, highly critical products with short operation life, the applicability of design engineering approach to dependability, the effect of the genesis on the assurance of design engineering dependability, behavioural models of technical products in terms of dependability and specifics of highly critical product calculation. It was identified that, for items with high specified probability of no failure exceeding three-sigma random value variation interval, dependability is to be calculated not by identifying the dependability function, but rather by proving that undependability function is below the acceptable value, which ultimately ensures the specified dependability. Such approach enables the development of methods of early failure prevention using procedures of design engineering analysis of dependability for the purpose of achieving the required parameters of functionality, operability and dependability of products on the basis of a generalised parametric functional model. Results. The design engineering analysis of dependability allows substantiating the criteria for error-free design (selection of sound principles of operability and validation of engineering solutions for achieving the required dependability indicators). The effect of the error-free engineering criteria combined with the criteria for defect-free engineering (observance of the generally accepted principles, rules, requirements, norms and standards of drawing generation) and defect-free manufacture (strict adherence to the requirements of drawings with no deviation permits) enables a designer to achieve the specified dependability values without using the statistical methods of the modern dependability theory. Conclusion. Dependability as a comprehensive property is characterised by a probability that, on the one hand, determines the rate of possible failures, and, on the other hand, indicates the number of errors that were made by engineers during the design, manufacture and operation of products and can lead to failures. Additionally, the failure rate is determined by the engineers’ efforts to eliminate or mitigate the consequences of possible failures at each life cycle stage. The greater and earlier are such efforts adopted, the higher the product’s dependability will be. Ultimately, dependability is determined by consistent and rigorous implementation of error-free design, defect-free design and defect-free manufacture procedures whose efficiency is in no way associated with the number of manufactured products. Their efficiency and effectiveness are determined by specific decisions and actions by the engineers who make sure that the product performs the required functions with the specified dependability in the established modes and conditions of operation. Ensuring that only takes using engineering disciplines, as well as design engineering methods for quality and dependability assurance.

Dependability from a designer’s standpoint

The Aim of the paper is to let the reader look at dependability through the eyes of a designer who is to develop an entity with specified dependability requirements. The result of such work is not yet dependability as a property, but the ability proper to a structure, without which the required dependability cannot manifest itself. Designing highly dependable entities requires the use of formalized practices with specific operating procedures, that, on the one hand, do not contradict the provisions of the dependability theory, while, on the other hand, are to be useful, clear and easy-to-understand by any designer in order to ensure the required dependability. Methods . The paper examines the primary approaches that allow a designer, without violating the existing notions and terminology of dependability, solving problems of technical object dependability in the course of design and development based on engineering disciplines and design methods intended to ensure the dependability of products, starting with the very early life cycle stages. If such approaches to dependability research are employed, preventing failures only requires the application of the principles of physicality (causal connections) and physical necessity (consistency with the laws of nature) of the causes of failures. Results . The paper sets forth simple mathematical models that helped create a generalized parametric model of complex technical systems operation. Based on the cited models, it can be concluded that dependability calculation in terms of the known dependability indicators of components and elements can be replaced with dependability estimation in terms of the probability of performance by the components and elements of the required functions. This conclusion not only does not contradict the provisions of the dependability theory, but makes dependability an effective tool helping the designer ensure the specified dependability. The generalized parametric model of operation is solved using the method of design and process dependability analysis developed for the purpose of analyzing and assessing design solutions as part of high-dependability item design. Conclusion . The concepts, approaches, models and methods suggested in the paper allow the designer to take dependability as operability expanded in time. Such dependability is always specific and takes into consideration all the distinctive features of an entity. In this case, the process of design and assurance of dependability becomes an integral part of the entity creation activities regardless of uniqueness, series production, availability of dependability indicators of components and elements. But most importantly, such approach to dependability, on the one hand, does not contradict the foundations of the modern dependability theory, and, on the other hand, relieves the designer of the impression that dependability is something foreign, not associated with the real design.

Using Evidence-based Arguments to Support Dependability Assurance - Experiences and Challenges

The presentation introduces to the problem of evidencebased arguments and their applications. Then, based on the experiences collected during development and commercial deployment of a concrete solution to this problem (system NOR-STA) we overview selected challenges and the ways of addressing them.

New Opportunities for Integrated Formal Methods

Formal methods have provided approaches for investigating software engineering fundamentals and also have high potential to improve current practices in dependability assurance. In this article, we summarise known strengths and weaknesses of formal methods. From the perspective of the assurance of robots and autonomous systems (RAS), we highlight new opportunities for integrated formal methods and identify threats to the adoption of such methods. Based on these opportunities and threats, we develop an agenda for fundamental and empirical research on integrated formal methods and for successful transfer of validated research to RAS assurance. Furthermore, we outline our expectations on useful outcomes of such an agenda.

Semantic Data Management in IT Service Performance Assurance

In today's dynamic and highly composed environments, IT service performance and dependability assurance require efficient reasoning about the performance and dependability effects of faults and the countermeasures to choose, using limited knowledge. Model- and observation-based qualitative error propagation analysis methods can be applied to this end; however, providing support for the human, as well as conceptually structured machine interpretation of sets of competing error propagation hypotheses is an open problem. This paper proposes the application of Formal Concept Analysis (FCA) for these tasks. A natural way to represent error propagation hypothesis sets as formal contexts is proposed, and the visual diagnostic exploration of formal context lattices is introduced. On this basis, potential applications of FCA in performance and dependability assurance activities are characterized.

An effective method for service components selection based on micro-canonical annealing considering dependability assurance

Distributed virtualization changes the pattern of building software systems. However, it brings some problems on dependability assurance owing to the complex social relationships and interactions between service components. The best way to solve the problems in a distributed virtualized environment is dependable service components selection. Dependable service components selection can be modeled as finding a dependable service path, which is a multiconstrained optimal path problem. In this paper, a service components selection method that searches for the dependable service path in a distributed virtualized environment is proposed from the perspective of dependability assurance. The concept of Quality of Dependability is introduced to describe and constrain software system dependability during dynamic composition. Then, we model the dependable service components selection as a multiconstrained optimal path problem, and apply the Adaptive Bonus-Penalty Microcanonical Annealing algorithm to find the optimal dependable service path. The experimental results show that the proposed algorithm has high search success rate and quick converges.

Towards Automated Log Parsing for Large-Scale Log Data Analysis

Logs are widely used in system management for dependability assurance because they are often the only data available that record detailed system runtime behaviors in production. Because the size of logs is constantly increasing, developers (and operators) intend to automate their analysis by applying data mining methods, therefore structured input data (e.g., matrices) are required. This triggers a number of studies on log parsing that aims to transform free-text log messages into structured events. However, due to the lack of open-source implementations of these log parsers and benchmarks for performance comparison, developers are unlikely to be aware of the effectiveness of existing log parsers and their limitations when applying them into practice. They must often reimplement or redesign one, which is time-consuming and redundant. In this paper, we first present a characterization study of the current state of the art log parsers and evaluate their efficacy on five real-world datasets with over ten million log messages. We determine that, although the overall accuracy of these parsers is high, they are not robust across all datasets. When logs grow to a large scale (e.g., 200 million log messages), which is common in practice, these parsers are not efficient enough to handle such data on a single computer. To address the above limitations, we design and implement a parallel log parser (namely POP) on top of Spark, a large-scale data processing platform. Comprehensive experiments have been conducted to evaluate POP on both synthetic and real-world datasets. The evaluation results demonstrate the capability of POP in terms of accuracy, efficiency, and effectiveness on subsequent log mining tasks.

Yielding optimized dependability assurance through bit inversion

Phase change memory (PCM) is a promising alternative to conventional DRAM main memories, due to its read performance, density, and nonvolatility and resulting low static energy. Unfortunately, reliability is still a significant challenge as limited write endurance, exacerbated by process variation, leads to increasing numbers of stuck-at faults over the memory's lifetime. This includes a significant number of stuck-at faults that appear early in the memory's service. Error-correcting Pointers (ECP) is a popular proposal to mitigate stuck-at faults in PCM by recording the addresses and the values of faulty bits in order to extend the lifetime of the memory. We propose a method to extend the effectiveness of ECP coverage called Yoda, which utilizes a small number of additional encoding bits in order to dramatically improve the effectiveness and fault correction capability of ECP. By adding one additional bit to ECP which corrects f faults, Yoda can correct 2f +1 faults. Further improvements are possible introducing small numbers additional bits. Our simulation results demonstrate that Yoda has a 3.0× improvement in fault coverage compared to a fault-aware ECP with a similar overhead, while also providing a 2.5–3.0× improvement over state-of-the-art schemes with comparable complexity. Furthermore, Yoda provides a method to protect the auxiliary bits, also with a small overhead. By adding one auxiliary bit to protect the auxiliary bits, Yoda can achieve extra improvement.

Practical application of continuous distribution laws in the theory of reliability of technical systems

Aim. One of the stages of dependability analysis of technical systems is the a priori analysis that is usually performed at early design stages. This analysis a priori has known quantitative dependability characteristics of all used system elements. As unique, non-mass produced or new elements usually lack reliable a priori information on quantitative dependability characteristics, those are specified based on the characteristics of technical elements already in use. A priori information means information retrieved as the result of dependability calculation and simulation, various dependability tests, operation of facilities similar in design to the tested ones (prototypes). From system perspective, any research of technical object dependability must be planned and performed subject to the results of previous research, i.e. the a priori information. Thus, the a priori analysis is based on a priori (probabilistic) dependability characteristics that only approximately reflect the actual processes occurring in the technical system. Nevertheless, at the design stage, this analysis allows identifying system element connections that are poor from dependability point of view, taking appropriate measures to eliminate them, as well as rejecting unsatisfactory structural patterns of technical systems. That is why a priori dependability analysis (or calculation) is of significant importance in the practice of technical system design and is an integral part of engineering projects. This paper looks into primary [1] continuous distributions of random values (exponential, Weibull-Gnedenko, gamma, log normal and normal) used as theoretical distributions of dependability indicators. In order to obtain a priori information on the dependability of technical systems and elements under development, the authors present dependences that allow evaluating primary dependability indicators, as well as show approaches to their application in various conditions. Methods. Currently, in Russia there is no single system for collection and processing of information on the dependability of diverse technical systems [3] which is one of the reasons of low dependability. In the absence of such information, designing new systems with specified dependability indicators is associated with significant challenges. That is why the information presented in this article is based upon the collection and systematization of information published in Russian sources, analysis of the results of simulation and experimental studies of dependability of various technical systems and elements, as well as statistical materials collected in operation. Results. The article presents an analysis of practical application of principal continuous laws of random distribution in the theory of technical systems dependability that allows hypothesizing the possible shape of system elements failure models at early design stages for subsequent evaluation of their dependability indicators. Conclusions. The article may be useful to researchers at early stages of design of various technical systems as a priori information for construction of models and criteria used for dependability assurance and monitoring, as well as improvement of accuracy and reliability of derived estimates in the process of highly reliable equipment (systems) development.

Dependability Assurance Framework Standardization for Safety-Sensitive Consumer Devices at the OMG

This paper introduces a new effort by the Object Management Group to standardise the format of information used in the assurance of safety-sensitive consumer devices, such as automobiles and service robots. The diversity of device types and development approaches for such devices makes the sharing and re-use of assurance information difficult. The new standardisation effort aims to resolve this issue through common information models and consistent argument structures.

Genetic Algorithms for the Dependability Assurance in the Design of a Long‐Span Suspension Bridge

Abstract: A long‐span suspension bridge is a complex structural system that interacts with the surrounding environment and the users. The environmental actions and the corresponding loads (wind, temperature, rain, earthquake, etc.) together with the live loads (railway traffic, highway traffic), have a strong influence on the dynamic response of the bridge, and can significantly influence the structural behavior and alter its geometry, thus limiting the serviceability performance even up to a partial closure. This article will present some general considerations and operative aspects of the activities related to the analysis and design of such a complex structural system. Specific reference is made to the dependability assessment and the performance requirements of the whole system, while focus is given on methods for handling the completeness and the uncertainty in the assessment of the load scenarios. Aiming at the serviceability assessment, a method based on the combined application of genetic algorithms and a finite element method (FEM) investigation is proposed and applied.

Automated aspect-oriented decomposition of process-control systems for ultra-high dependability assurance

This paper presents a method for decomposing process-control systems. This decomposition method is automated, meaning that a series of principles that can be evolved to support automated tools are given to help a designer decompose complex systems into a collection of simpler components. Each component resulting from the decomposition process can be designed and implemented independently of the other components. Also, these components can be tested or verified by the end-user independently of each other. Moreover, the system properties, such as safety, stability, and reliability, can be mathematically inferred from the properties of the individual components. These components are referred to as IDEAL (independently developable end-user assessable logical) components. This decomposition method is applied to a case study specified by the High-Integrity Systems group at Sandia National Labs, which involves the control of a future version of the Bay Area Rapid Transit (BART) system.

DEPENDABLE SOFTWARE IN RAILWAY SIGNALLING

Railway signalling software and safety requirements are summarized, and three short examples of the application of new methods to the assurance of dependability are provided. The strengths and shortcomings of existing methods relative to application needs are illustrated. The analogy between railway signalling and other distribution processes in manufacturing and supply chain management is noted.

Development of international risk analysis standards

The International Electrotechnical Commission's (IEC) Technical Committee 56 “Dependability” develops international standards on dependability as well as risk analysis. IEC is primarily working in the electrotechnical field, but IEC dependability standards are valid in all technical fields. IEC 60300 standards consists of umbrella documents, application guides and tools. The umbrella documents IEC 60300-1 and 60300-2 on dependability assurance and dependability programme elements and tasks are expected to become very important, along with related application guides, because they will be linked to ISO 9000 quality system standards. TC 56 has developed a number of standards applicable to risk analysis of technological systems. An overview of existing risk analysis standards and a short description of some standards is presented.

A multi-level view of dependable computing

This paper serves a dual purpose. It presents a unified framework and terminology for the study of computer system dependability. It also surveys the field of dependable computing in light of the proposed framework. Specifically, impairments to dependability are viewed from six levels, each being more abstract than the previous one. It is argued that all of these levels are useful, in the sense that proven dependability assurance techniques can be applied at each level, and that it is beneficial to have distinct, precisely defined terminology for describing impairments to, and procurement strategies for, computer system dependability at these levels. The six levels are: 1. Defect level or component level, dealing with deviant atomic parts. 2. Fault level or logic level, dealing with deviant signal values or path selections. 3. Error level or information level, dealing with deviant data or internal states. 4. Malfunction level or system level, dealing with deviant functional behavior. 5. Degradation level or service level, dealing with deviant performance. 6. Failure level or result level, dealing with deviant outputs or actions. Briefly, a hardware or software component may be defective (hardware may also become defective due to war and aging). Certain system states will expose the defect, resulting in the development of faults defined as incorrect signal values or decisions within the system. If a fault is actually exercised, it may contaminate the data flowing within the system, causing errors. Erroneous information or states may or may not cause the affected subsystem to malfunction, depending on the subsystem's design and error tolerance. A subsystem malfunction does not necessarily have a catastrophic, unsafe, or even perceivable service-level effect. Finally, degradation of service could eventually lead to system failure. At each of these six levels, the complementary approaches of prevention (avoidance or removal) and tolerance are discussed in relation to inter-level transitions.

Field dependability evaluation principles

The overall objective for the dependability assurance of Ericsson's main product, the AXE switching system, is delivery of a product with agreed reliability and maintainability performances, and the provisioning of maintenance support with agreed characteristics. The fulfillment of these objectives is evaluated through monitoring of a set of characteristic measures for quality and dependability during the operations and maintenance phase. The AXE system is in operation in some 70 countries all over the globe. A system for field monitoring thus requires a standardized set of measures and evaluation principles. This standardization is accomplished by a common software tool, DEPEND, used for various dependability calculation needs throughout the product life cycle. The author presents the principles, procedures, and tools used for data collection, registration, storage, and presentation. >