Iterative development and changing requirements: drivers of variability in an industrial system for veterinary anesthesia

Developing a safety-critical embedded system poses a high risk, since such systems must usually comply with (potentially changing) rigorous standards set by customers and legal authorities. To reduce risk and cope with changing requirements, manufacturers of embedded devices increasingly use iterative development processes and prototyping both for hard- and firmware. However, hard- and firmware development are difficult to align in a common process, because hardware development cycles are typically longer and more expensive. Thus, seamlessly transitioning software to new hardware revisions and reusing old hardware revisions can be problematic. In this paper, we describe an industrial case study for veterinary anesthesia in which we also faced this problem. To solve it, we introduced preprocessor-based variability to create a small configurable system that could flexibly adapt to our needs. We discuss our solution, alternative solutions for hardware evolution, as well as their pros and cons. Our experiences generalize an interesting evolution scenario for systems that are planned and delivered as a single system, but exhibited variability to cope with problems during agile development processes.