  Safety-critical software systems are those whose failure or malfunction could
result in casualty and/or serious financial loss. In such systems, safety
assurance cases (SACs) are an emerging approach that adopts a proactive
strategy to produce structuralized safety justifications and arguments. While
SACs are recommended in many software-intensive safety-critical domains, the
lack of knowledge regarding the practitioners' perspectives on using SACs
hinders effective adoption of this approach. To gain such knowledge, we
interviewed nine practitioners and safety experts who focused on
safety-critical software systems. In general, our participants found the SAC
approach beneficial for communication of safety arguments and management of
safety issues in a multidisciplinary setting. The challenges they faced when
using SACs were primarily associated with (1) a lack of tool support, (2)
insufficient process integration, and (3) scarcity of experienced personnel. To
overcome those challenges, our participants suggested tactics that focused on
creating direct safety arguments. Process and organizational adjustments are
also needed to streamline SAC analysis and creation. Finally, our participants
emphasized the importance of knowledge sharing about SACs across
software-intensive safety-critical domains.
