Universität Stuttgart
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Item Open Access An industrial case study on the evaluation of a safety engineering approach for software-intensive systems in the automotive domain(2016) Abdulkhaleq, Asim; Vöst, Sebastian; Wagner, Stefan; Thomas, JohnSafety remains one of the essential and vital aspects in today's automotive systems. These systems, however, become ever more complex and dependent on software which is responsible for most of their critical functions. Therefore, the software components need to be analysed and verified appropriately in the context of software safety. The complexity of software systems makes defining software safety requirements with traditional safety analysis techniques difficult. A new technique called STPA (Systems-Theoretic Process Analysis) based on system and control theory has been developed by Leveson to cope with complex systems. Based on STPA, we have developed a comprehensive software safety engineering approach in which the software and safety engineers integrate the analysis of software risks with their verification to recognize the software-related hazards and reduce the risks to a low level. In this paper, we explore and evaluate the application of our approach to a real industrial system in the automotive domain. The case study was conducted analysing the software controller of the Active Cruise Control System (ACC) of the BMW Group.Item Open Access An automatic safety-based test case generation approach based on systems-theoretic process analysis(2016) Abdulkhaleq, Asim; Wagner, StefanSoftware safety remains one of the essential and vital aspects in today’s systems. Software is becoming responsible for most of the critical functions of systems. Therefore, the software components in the systems need to be tested extensively against their safety requirements to ensure a high level of system safety. However, performing testing exhaustively to test all software behaviours is impossible. Numerous testing approaches exist. However, they do not directly concern the information derived during the safety analysis. STPA (Systems-Theoretic Process Analysis) is a unique safety analysis approach based on system and control theory, and was developed to identify unsafe scenarios of a complex system including software. In this paper, we present a testing approach based on STPA to automatically generate test cases from the STPA safety analysis results to help software and safety engineers to recognize and reduce the associated software risks. We also provide an open-source safety-based testing tool called STPA TCGenerator to support the proposed approach. We illustrate the proposed approach with a prototype of a software of the Adaptive Cruise Control System (ACC) with a stop-and-go function with a Lego-Mindstorms EV3 robot.Item Open Access Naming the pain in requirements engineering: a design for a global family of surveys and first results from Germany(2015) Méndez Fernández, Daniel; Wagner, StefanContext: For many years, we have observed industry struggling in defining a high quality requirements engineering (RE) and researchers trying to understand industrial expectations and problems. Although we are investigating the discipline with a plethora of empirical studies, they still do not allow for empirical generalisations. Objective: To lay an empirical and externally valid foundation about the state of the practice in RE, we aim at a series of open and reproducible surveys that allow us to steer future research in a problem-driven manner. Method: We designed a globally distributed family of surveys in joint collaborations with different researchers and completed the first run in Germany. The instrument is based on a theory in the form of a set of hypotheses inferred from our experiences and available studies. We test each hypothesis in our theory and identify further candidates to extend the theory by correlation and Grounded Theory analysis. Results: In this article, we report on the design of the family of surveys, its underlying theory, and the full results obtained from Germany with participants from 58 companies. The results reveal, for example, a tendency to improve RE via internally defined qualitative methods rather than relying on normative approaches like CMMI. We also discovered various RE problems that are statistically significant in practice. For instance, we could corroborate communication flaws or moving targets as problems in practice. Our results are not yet fully representative but already give first insights into current practices and problems in RE, and they allow us to draw lessons learnt for future replications. Conclusion: Our results obtained from this first run in Germany make us confident that the survey design and instrument are well-suited to be replicated and, thereby, to create a generalisable empirical basis of RE in practice.Item Open Access Introduction of static quality analysis in small- and medium-sized software enterprises: experiences from technology transfer(2014) Gleirscher, Mario; Golubitskiy, Dmitriy; Irlbeck, Maximilian; Wagner, StefanToday, small- and medium-sized enterprises (SMEs) in the software industry face major challenges. Their resource constraints require high efficiency in development. Furthermore, quality assurance (QA) measures need to be taken to mitigate the risk of additional, expensive effort for bug fixes or compensations. Automated static analysis (ASA) can reduce this risk because it promises low application effort. SMEs seem to take little advantage of this opportunity. Instead, they still mainly rely on the dynamic analysis approach of software testing. In this article, we report on our experiences from a technology transfer project. Our aim was to evaluate the results static analysis can provide for SMEs as well as the problems that occur when introducing and using static analysis in SMEs. We analysed five software projects from five collaborating SMEs using three different ASA techniques: code clone detection, bug pattern detection and architecture conformance analysis. Following the analysis, we applied a quality model to aggregate and evaluate the results. Our study shows that the effort required to introduce ASA techniques in SMEs is small (mostly below one person-hour each). Furthermore, we encountered only few technical problems. By means of the analyses, we could detect multiple defects in production code. The participating companies perceived the analysis results to be a helpful addition to their current QA and will include the analyses in their QA process. With the help of the Quamoco quality model, we could efficiently aggregate and rate static analysis results. However, we also encountered a partial mismatch with the opinions of the SMEs. We conclude that ASA and quality models can be a valuable and affordable addition to the QA process of SMEs.Item Open Access Links between the personalities, styles and performance in computer programming(2015) Karimi, Zahra; Baraani-Dastjerdi, Ahmad; Ghasem-Aghaee, Nasser; Wagner, StefanThere are repetitive patterns in strategies of manipulating source code. For example, modifying source code before acquiring knowledge of how a code works is a depth-first style whereas reading and understanding before modifying source code is a breadth-first style. To the extent we know, there is no study on the influence of personality on them. The objective of this study is to understand the influence of personality on programming styles. We did a correlational study with 65 programmers at the University of Stuttgart. Academic achievement, programming experience, attitude towards programming, and five personality factors were measured via self-assessed survey. The programming styles were asked for in the survey or mined from the software repositories. Performance in programming was composed of bug-proneness of programmers which was mined from software repositories, the grades they got in a software project course and their estimate of their own programming ability. In a statistical analysis we found that Openness to Experience has a positive association with breadth-first style and Conscientiousness has a positive association with depth-first style. We also found that, in addition to having more programming experience and better academic achievement, the styles of working depth-first and saving coarse-grained revisions improve performance in programming.Item Open Access At ease with your warnings: the principles of the salutogenesis model applied to automatic static analysis(2016) Ostberg, Jan-Peter; Wagner, StefanThe results of an automatic static analysis run can be overwhelming, especially for beginners. The overflow of information and the resulting need for many decisions is mentally tiring and can cause stress symptoms. There are several models in health care which are designed to fight stress. One of these is the salutogenesis model created by Aaron Antonovsky. In this paper, we will present an idea on how to transfer this model into a triage and recommendation model for static analysis tools and give an example of how this can be implemented in FindBugs, a static analysis tool for Java.Item Open Access Rapid quality assurance with requirements smells(2016) Femmer, Henning; Méndez Fernández, Daniel; Wagner, Stefan; Eder, SebastianContext: Bad requirements quality can cause expensive consequences during the software development lifecycle, especially if iterations are long and feedback comes late. Objectives: We aim at a light-weight static requirements analysis approach that allows for rapid checks immediately when requirements are written down. Method: We transfer the concept of code smells to Requirements Engineering as Requirements Smells. To evaluate the benefits and limitations, we define Requirements Smells, realize our concepts for a smell detection in a prototype called Smella and apply Smella in a series of cases provided by three industrial and a university context. Results: The automatic detection yields an average precision of 59% at an average recall of 82% with high variation. The evaluation in practical environments indicates benefits such as an increase of the awareness of quality defects. Yet, some smells were not clearly distinguishable. Conclusion: Lightweight smell detection can uncover many practically relevant requirements defects in a reasonably precise way. Although some smells need to be defined more clearly, smell detection provides a helpful means to support quality assurance in Requirements Engineering, for instance, as a supplement to reviews.Item Open Access Operationalised product quality models and assessment: the Quamoco approach(2015) Wagner, Stefan; Goeb, Andreas; Heinemann, Lars; Kläs, Michael; Lampasona, Constanza; Lochmann, Klaus; Mayr, Alois; Plösch, Reinhold; Seidl, Andreas; Streit, Jonathan; Trendowicz, AdamContext: Software quality models provide either abstract quality characteristics or concrete quality measurements; there is no seamless integration of these two aspects. Quality assessment approaches are, hence, also very specific or remain abstract. Reasons for this include the complexity of quality and the various quality profiles in different domains which make it difficult to build operationalised quality models. Objective: In the project Quamoco, we developed a comprehensive approach aimed at closing this gap. Method: The project combined constructive research, which involved a broad range of quality experts from academia and industry in workshops, sprint work and reviews, with empirical studies. All deliverables within the project were peer-reviewed by two project members from a different area. Most deliverables were developed in two or three iterations and underwent an evaluation. Results: We contribute a comprehensive quality modelling and assessment approach: (1) A meta quality model defines the structure of operationalised quality models. It includes the concept of a product factor, which bridges the gap between concrete measurements and abstract quality aspects, and allows modularisation to create modules for specific domains. (2) A largely technology-independent base quality model reduces the effort and complexity of building quality models for specific domains. For Java and C# systems, we refined it with about 300 concrete product factors and 500 measures. (3) A concrete and comprehensive quality assessment approach makes use of the concepts in the meta-model. (4) An empirical evaluation of the above results using real-world software systems showed: (a) The assessment results using the base model largely match the expectations of experts for the corresponding systems. (b) The approach and models are well understood by practitioners and considered to be both consistent and well suited for getting an overall view on the quality of a software product. The validity of the base quality model could not be shown conclusively, however. (5) The extensive, open-source tool support is in a mature state. (6) The model for embedded software systems is a proof-of-concept for domain-specific quality models. Conclusion: We provide a broad basis for the development and application of quality models in indus- trial practice as well as a basis for further extension, validation and comparison with other approaches in research.