05 Fakultät Informatik, Elektrotechnik und Informationstechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6
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Item Open Access Mining Java packages for developer profiles : an exploratory study(2017) Ramadani, Jasmin; Wagner, StefanItem Open Access A comprehensive safety engineering approach for software-intensive systems based on STPA(2015) Abdulkhaleq, Asim; Wagner, Stefan; Leveson, NancyFormal verification and testing are complementary approaches which are used in the development process to verify the functional correctness of software. However, the correctness of software cannot ensure the safe operation of safety-critical software systems. The software must be verified against its safety requirements which are identified by safety analysis, to ensure that potential hazardous causes cannot occur. The complexity of software makes defining appropriate software safety requirements with traditional safety analysis techniques difficult. STPA (Systems-Theoretic Processes Analysis) is a unique safety analysis approach that has been developed to identify system hazards, including the software-related hazards. This paper presents a comprehensive safety engineering approach based on STPA, including software testing and model checking approaches for the purpose of developing safe software. The proposed approach can be embedded within a defined software engineering process or applied to existing software systems, allow software and safety engineers integrate the analysis of software risks with their verification. The application of the proposed approach is illustrated with an automotive software controller.Item Open Access Scrum for cyber-physical systems: a process proposal(2014) Wagner, StefanAgile development processes and especially Scrum are chang- ing the state of the practice in software development. Many companies in the classical IT sector have adopted them to successfully tackle various challenges from the rapidly changing environments and increasingly complex software systems. Companies developing software for embedded or cyber-physical systems, however, are still hesitant to adopt such processes. Despite successful applications of Scrum and other agile methods for cyber-physical systems, there is still no complete process that maps their specific challenges to practices in Scrum. We propose to fill this gap by treating all design artefacts in such a development in the same way: In software development, the final design is already the product, in hardware and mechanics it is the starting point of production. We sketch the Scrum extension Scrum CPS by showing how Scrum could be used to develop all design artefacts for a cyber physical system. Hardware and mechanical parts that might not be available yet are simulated. With this approach, we can directly and iteratively build the final software and produce detailed models for the hardware and mechanics production in parallel. We plan to further detail Scrum CPS and apply it first in a series of student projects to gather more experience before testing it in an industrial case study.Item Open Access The Quamoco product quality modelling and assessment approach(2012) Wagner, Stefan; Lochmann, Klaus; Heinemann, Lars; Kläs, Michael; Trendowicz, Adam; Plösch, Reinhold; Seidl, Andreas; Goeb, Andreas; Streit, JonathanPublished software quality models either provide abstract quality attributes or concrete quality assessments. There are no models that seamlessly integrate both aspects. In the project Quamoco, we built a comprehensive approach with the aim to close this gap. For this, we developed in several iterations a meta quality model specifying general concepts, a quality base model covering the most important quality factors and a quality assessment approach. The meta model introduces the new concept of a product factor, which bridges the gap between concrete measurements and abstract quality aspects. Product factors have measures and instruments to operationalise quality by measurements from manual inspection and tool analysis. The base model uses the ISO 25010 quality attributes, which we refine by 200 factors and 600 measures for Java and C# systems. We found in several empirical validations that the assessment results fit to the expectations of experts for the corresponding systems. The empirical analyses also showed that several of the correlations are statistically significant and that the maintainability part of the base model has the highest correlation, which fits to the fact that this part is the most comprehensive. Although we still see room for extending and improving the base model, it shows a high correspondence with expert opinions and hence is able to form the basis for repeatable and understandable quality assessments in practice.Item Open Access XSTAMPP: An eXtensible STAMP platform as tool support for safety engineering(2015) Abdulkhaleq, Asim; Wagner, StefanSTPA (Systems-Theoretic Processes Analysis) is a new hazard analysis technique based on STAMP. STPA is already being used in different industrial domains (e.g. space, aviation, medical or automotive). To support the application of STPA and make using STPA more efficient, we developed an open tool called A-STPA. However, the current usage of ASTPA by safety analysts in different areas shows a number of shortcomings in terms of documenting unsafe control actions, drawing different levels of control structure diagrams, documenting the causal factors in STPA Step 2 and supporting the application of STPA in different areas. In this paper, we present an extensible STAMP platform called XSTAMPP as tool support designed specifically to serve the widespread adoption and use of STPA in different areas, to facilitate STPA application to different systems and to be easily extended to include different requirements and features. Moreover, XSTAMPP has the potential to be extended in the future to support the application of CAST for accident analysis. We believe that XSTAMPP is a useful first step toward establishing a base platform to support the application of STAMP methodologies in different domains.Item Open Access Towards applying a safety analysis and verification method based on STPA to agile software development(2016) Wang, Yang; Wagner, StefanThis paper presents a novel agile process model "S-Scrum" based on the existing development process "Safe Scrum" and extended by a safety analysis method and a safety verification approach based on STPA (System-Theoretic Process Analysis).Item Open Access Towards building knowledge on causes of critical requirements engineering problems(2015) Kalinowski, Marcos; Spínola, Rodrigo Oliveira; Conte, Tayana; Prikladnicki, Rafael; Méndez Fernández, Daniel; Wagner, Stefan[Context] Many software projects fail due to problems in requirements engineering (RE). [Objective] The goal of this paper is to gather information on relevant RE problems and to represent knowledge on their most common causes. [Method] We replicated a global family of RE surveys in the Brazil and used the data to identify critical RE problems and to build probabilistic cause-effect diagrams to represent knowledge on their common causes. [Results] The survey was answered by 74 different organizations, including small, medium and very large sized companies, conducting both, plan-driven and agile development. The most critical RE problems, according to those organizations, are related to communication and to incomplete or underspecified requirements. We provide the full probabilistic cause-effect diagrams with knowledge on common causes of the most critical identified RE problems online. [Conclusion] We believe that the knowledge presented in the diagrams can be helpful to support organizations in conducting causal analysis sessions by providing an initial understanding on what usually causes critical RE problems.Item Open Access Experiences with applying STPA to software-intensive systems in the automotive domain(2013) Abdulkhaleq, Asim; Wagner, StefanHazard analysis is one of the most important elements in developing safe-critical systems. STPA (Systems-Theoretic Process Analysis) is a modern technique based on the new accident causation model STAMP (System-Theoretic Accident Model and Process) for analyzing hazard and safety issues, which can be applied early in the design process of a system to achieve an acceptable risk level. We have applied STPA to a well-known example of safety-critical systems in the automotive industries: Adaptive Cruise Control (ACC). The results of the application of STPA to our case study and the limitations and difficulties of applying STPA are presented.Item Open Access Where do we stand in requirements engineering improvement today? : first results from a mapping study(2014) Méndez Fernández, Daniel; Ognawala, Saahil; Wagner, Stefan; Daneva, MayaRequirements engineering process improvement (REPI) approaches have gained much attention in research and practice. So far, however, there is no comprehensive view on the research in REPI in terms of solutions and current state of reported evidence. This paper aims to provide an overview on the existing solutions, their underlying principles and their research type facets, i.e. their state of empirical evidence. To this end, we conducted a systematic mapping study of the REPI publication space. This paper reports on the first findings regarding research type facets of the contributions as well as selected methodological principles. We found a strong focus in the existing research on solution proposals for REPI approaches that concentrate on normative assessments and benchmarks of the RE activities rather than on holistic RE improvements according to individual goals of companies. We conclude, so far, that there is a need to broaden the work and to investigate more problem-driven REPI which also targets the improvement of the quality of the underlying RE artefacts.Item Open Access The use of application scanners in software product quality assessment(2011) Wagner, StefanSoftware development needs continuous quality control for a timely detection and removal of quality problems. This includes frequent quality assessments, which need to be automated as far as possible to be feasible. One way of automation in assessing the security of software are application scanners that test an executing software for vulnerabilities. At present, common quality assessments do not integrate such scanners for giving an overall quality statement. This paper presents an integration of application scanners into a general quality assessment method based on explicit quality models and Bayesian nets. Its applicability and the detection capabilities of common scanners are investigated in a case study with two open-source web shops.