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Safety-critical software systems have traditionally been found in the aerospace-, nuclear- andmedical domains. As technology advances and software complexity increases, such systemscan be found in more and more applications, e.g. self driving cars. These systems need to meetexceptionally strict standards in terms of dependability. Proving compliance is a challenge forthe industry. The regulatory bodies often require a certain amount of testing to be performed butdo not require evidence of a given failure rate (which for software is hard to deal with comparedto hardware). This Licentiate thesis discusses how to quantify test results and analyses whatconclusions can be drawn from a given test effort, in terms of remaining faults in the software.

<p> Many safety-critical software applications are hard real-time systems. They have stringent timing requirements that have to be met. We present descriptions of timing behaviors that include precise definitions as well as analysis of how functional timing requirements (FTRs) interact with performance timing requirements (PTRs), and how these concepts can be used by software designers. The definitions explicitly show how to specify timing requirements with tolerances on time durations. </p> <p> This thesis shows the importance of specifying both FTRs and PTRs, by revealing the fact that their interaction directly determines the final implementability of real-time systems. By studying this interaction under three environmental assumptions, we find that the implementability results of the timing properties are different in each environment, but they are closely related. The results allow us to predict the system's implementability without developing or verifying the actual implementation. This also shows that we can sometimes significantly reduce the sampling frequency on the target platform, and still implement the timing requirement correctly. </p> <p> We present a component-based approach to formalizing common timing requirements and provide a pre-verified implementation of one of these requirements. The verification is performed using the theorem proving tool PVS. This allows domain experts to specify the tolerance in each individual timing requirement precisely. The pre-verified implementation of a timing requirement is demonstrated by applying the method in two examples. These examples show that both the design and verification effort are reduced significantly using a pre-verified template. </p> <p> A primary focus of this thesis is on how to include tolerances on timing durations in the specification, implementation and verification of timing behaviors in hard real-time applications. </p> / Thesis / Doctor of Philosophy (PhD)

Formal methods is a discipline of using a collection of mathematical techniques and formalisms to model and analyze software systems. Motivated by the new formal methods-based certification recommendations for safety-critical embedded software and the significant increase in the cost of verification and validation (V\&V), this research is about creating a software development process for control systems that can provide mathematical guarantees of high-level functional properties on the code. The process, dubbed credible autocoding, leverages control theory in the automatic generation of control software documented with proofs of their stability and performance. The main output of this research is an automated, credible autocoding prototype that transforms the Simulink model of the controller into C code documented with a code-level proof of the stability of the controller. The code-level proof, expressed using a formal specification language, are embedded into the code as annotations. The annotations guarantee that the auto-generated code conforms to the input model to the extent that key properties are satisfied. They also provide sufficient information to enable an independent, automatic, formal verification of the auto-generated controller software.

For avionic systems, the safety requirements are stricter than for non-safety critical systems due to the severe consequences a failure could cause. Depending on the consequences of a failure, the software needs to fulfill different testing criterias. More critical software needs more extensive testing. The question is whether the extra testing activities performed for software of higher criticality level results in discovery of more faults. Mutation testing has been used in this thesis as a method to evaluate the quality of test suites of avionic applications from different safety critical levels. The results showed that the extra activities performed at the higher levels do not necessarily result in finding more faults.

La vérification de logiciels est une activité dont l'importance est cruciale pour les logiciels embarqués critiques. Les différentes approches envisageables peuvent être classées en quatre catégories : les méthodes d'analyse statique non formelles, les méthodes d'analyse statique formelles, les méthodes d'analyse dynamique non formelles et les méthodes d'analyse dynamique formelles. L'objectif de cette thèse est de vérifier des propriétés temporelles dans un cadre industriel, par analyse dynamique formelle.La contribution comporte trois parties. Un langage adapté à l'expression des propriétés à vérifier, tirées du contexte industriel d'Airbus, a été dé ni. Il repose notamment sur la logique temporelle linéaire mais également sur un langage d'expressions régulières.La vérification d'une propriété temporelle s'effectue sur une trace d'exécution d'un logiciel, générée à partir d'un cas de test pré-existant. L'analyse statique est utilisée pour générer la trace en fonction des informations nécessaires à la vérification de la propriété temporelle formalisée.Cette approche de vérification propose une solution pragmatique au problème posé par le caractère ni des traces considérées. Des adaptations et des optimisations ont également été mises en œuvre pour améliorer l'efficacité de l'approche et faciliter son utilisation dans un contexte industriel. Deux prototypes ont été implémentés,des expérimentations ont été menées sur différents logiciels d'Airbus. / Software Verification is decisive for embedded software. The different verification approaches can be classified in four categories : non formal static analysis,formal static analysis, non formal dynamic analysis and formal dynamic analysis.The main goal of this thesis is to verify temporal properties on real industrial applications,with the help of formal dynamic analysis.There are three parts for this contribution. A language, which is well adapted to the properties we want to verify in the Airbus context was defined. This language is grounded on linear temporal logic and also on a regular expression language.Verification of a temporal property is done on an execution trace, generated from an existing test case. Generation also depends on required information to verify the formalized property. Static analysis is used to generate the trace depending on the formalized property.The thesis also proposes a pragmatic solution to the end of trace problem. In addition,specific adaptations and optimisations were defined to improve efficiency and user-friendliness and thus allow an industrial use of this approach. Two applications were implemented. Some experiments were led on different Airbus software.

Date: 4th June 2023 Level: Master thesis in Product- and Process Development, advanced level, 30 credits Institution: School of Innovation, Design and Engineering at Mälardalen University Authors: Victor Busck Julia Eriksson Title: Improving Software Development Process Through Industry 4.0 Methodologies - A focus on Railway Embedded Software Supervisor: Yuji Yamamoto - Mälardalens University, Raluca Marinescu - Alstom, Ian Bird-Radolovic - Alstom Keywords: Safety-critical software development; Software development;Industry 4.0; Artificial Intelligence Purpose: The purpose of this study is to investigate what challenges and bottlenecks may occur in the development process of safety-critical software and suggest how Industry 4.0 technologies could be applied to overcome the bottlenecks and improve the process. Research questions: 1. What bottlenecks can the railway domain encounter when developing safety-critical software? 2. How can Industry 4.0 technologies be applied to overcome thebottlenecks and improve the development process of safety-critical software? Methodology: The study is based on a qualitative research methodology following an abductive approach. This led to the theoretical framework being gradually developed in parallel with the empirical data collection. The theoretical collection was based on scientific reports and books. The empirical data collection was based on a questionnaire, of which five in-depth interviews werethen conducted based on responses. Out of the five, three were semi-structured and two unstructured. Conclusion: The study concluded that all phases except design and implementation and software evaluation contained various bottlenecks related to tools, training, processes, resources and communication. However, it can be concluded that the testing phases were the biggest bottleneck at Alstom. To overcome testing challenges and improve the development process, the analysis shows that Industry 4.0 technologies such as AI, NLP and ML could be used to automate testing activities.

<p>The purpose of this thesis is to explore what software evaluation methods are currently available that can assist organizations and companies in procuring a software solution for some particular task or purpose for a specific type of business. The thesis is based on a real-world scenario where a company, Volvo Technology Corporation (VTEC), is in the process of selecting a new intellectual property management system for their patent department. For them to make an informed decision as to which system to choose, an evaluation of market alternatives needs to be done. First, a set of software evaluation methods and techniques are chosen for further evaluation. An organizational study, by means of interviews where questions are based on the ISO 9126-1 Software quality model, is then conducted, eliciting user opinions about the current system and what improvements a future system should have. The candidate methods are then evaluated based on the results from the organizational study and other pertinent factors in order to reach a conclusion as to which method is best suited for this selection problem. The Analytical Hierarchy Process (AHP) is deemed the best choice.</p>

The purpose of this thesis is to explore what software evaluation methods are currently available that can assist organizations and companies in procuring a software solution for some particular task or purpose for a specific type of business. The thesis is based on a real-world scenario where a company, Volvo Technology Corporation (VTEC), is in the process of selecting a new intellectual property management system for their patent department. For them to make an informed decision as to which system to choose, an evaluation of market alternatives needs to be done. First, a set of software evaluation methods and techniques are chosen for further evaluation. An organizational study, by means of interviews where questions are based on the ISO 9126-1 Software quality model, is then conducted, eliciting user opinions about the current system and what improvements a future system should have. The candidate methods are then evaluated based on the results from the organizational study and other pertinent factors in order to reach a conclusion as to which method is best suited for this selection problem. The Analytical Hierarchy Process (AHP) is deemed the best choice.