Cost and Efforts in Product Lines for Developing Safety Critical Products - An empirical study

Abstract: Reuse processes are considered nowadays as a very advantageous and beneficial approach that is frequently used in several industrial environments. This fact has strongly motivated practitioners to rely on Software Product Line Engineering principles. Using product lines is associated with both cost savings and reduced efforts for development in industry. Moreover, many companies and domains develop products nowadays that need to be safety certified before they can be sold to customers. In this perspective, there is industrial effort spent on addressing functional safety in product lines in industry. Different cost modeling approaches have been proposed in existing literature for providing solutions on software product line effort estimations. The main problem is that there is little evidence of cases in literature where such approaches have been applied successfully in industrial domains. In addition to that, no established product line cost model has been found in existing literature that considers functional safety efforts in its estimations. In this thesis report, an empirical study is presented which has the main focus on the investigation of cost and efforts in industrial product lines for developing safety-critical products. Besides the literature study which highlights related work and existing cost-modeling approaches for product lines, three studies are conducted in order to provide evidence and findings for identifying cost and efforts attributed to safety-critical product line development in industrial domains.  In the first study, semi-structured interviews are performed with practitioners and industrial experts at Volvo Construction Equipment. The structure of the interview study is influenced and inspired by the findings from the literature study on expert effort estimations and established product line cost models as well as the effort and cost areas they attribute to the overall product line effort. The main purpose of the interview study is to derive results on safety effort estimation based on the feedback provided by industrial experts regarding functional safety application in the construction equipment domain. The second study consists in a survey study which gathers information on how other domains (except Volvo CE) deal with functional safety in their product lines and aims to investigate functional safety effort in their product line development process. Finally, a documentation analysis (third conducted study) is performed at Volvo CE in order to provide more evidence for supporting the findings from case study 1.  The main contribution of this thesis work consists in the following: An overall analysis of the findings and results derived from the three conducted studies was provided in order to identify and explain the cost areas that contribute in the overall functional safety effort attested in industrial product lines. Moreover, several functional safety-related issues and challenges are identified while analyzing the three studies. Highest focus during this analysis regards their impact on cost in the functional safety perspective. Finally, we provide solutions on how to reduce this impact on cost by explaining the interdependencies between different safety-related cost areas, as well. The most important contribution of the analysis consists in the conclusions drawn from the investigation of functional safety effort estimation in product lines in industry. Previously, performing the literature study did not bring to the identification of any cost-modelling technique or estimation approach that is considering functional safety effort estimation in industry. For this reason, the results derived based on the findings in our empirical study are crucial in this perspective. In addition, we propose guidelines on proposing a new estimation approach in the future which would combine principles from both formal cost-modelling techniques as well as expert-based estimation methods which rely on the industrial expertise and human experience. We derive different components for the total functional safety effort in product lines from the findings in our empirical study. Moreover, different safety-related scenarios in industry and include safety effort estimations for each of them. The biggest contribution is however on the directions given on how to estimate in practice each of the functional safety effort components. Such directions are currently missing in existing effort estimation methods. Finally, proposals on how to improve further our analysis on product line safety effort estimation are given. Furthermore, we explain what is needed in addition in order to propose and design a relevant safety-related product line effort estimation approach in the future.