A Survey on the Interplay between Software Engineering and Systems Engineering during SoS Architecting

Background: The Systems Engineering and Software Engineering disciplines are highly intertwined in most modern Systems of Systems (SoS), and particularly so in industries such as defense, transportation, energy and health care. However, the combination of these disciplines during the architecting of SoS seems to be especially challenging; the literature suggests that major integration and operational issues are often linked to ambiguities and gaps between system-level and software-level architectures. Aims: The objective of this paper is to empirically investigate: 1) the state of practice on the interplay between these two disciplines in the architecting process of systems with SoS characteristics; 2) the problems perceived due to this interplay during said architecting process; and 3) the problems arising due to the particular characteristics of SoS systems. Method: We conducted a questionnaire-based online survey among practitioners from industries in the aforementioned domains, having a background on Systems Engineering, Software Engineering or both, and experience in the architecting of systems with SoS characteristics. The survey combined multiple-choice and open-ended questions, and the data collected from the 60 respondents were analyzed using quantitative and qualitative methods. Results: We found that although in most cases the software architecting process is governed by system-level requirements, the way requirements were specified by systems engineers, and the lack of domain-knowledge of software engineers, often lead to misinterpretations at software level. Furthermore, we found that unclear and/or incomplete specifications could be a common cause of technical debt in SoS projects, which is caused, in part, by insufficient interface definitions. It also appears that while the SoS concept has been adopted by some practitioners in the field, the same is not true about the existing and growing body of knowledge on the subject in Software Engineering resulting in recurring problems with system integration. Finally, while not directly related to the interplay of the two disciplines, the survey also indicates that low-level hardware components, despite being identified as the root cause of undesired emergent behavior, are often not considered when modeling or simulating the system. Conclusions: The survey indicates the need for tighter collaboration between the two disciplines, structured around concrete guidelines and practices for reconciling their differences. A number of open issues identified by this study require further investigation.