Requirements Engineering, part 2: A Practical Process for Safety-Critical Development

In this second part of our requirements engineering series, Jeff walks us through his preferred process for developing safety-critical products, particularly medical devices. We explore the crucial distinction between prototyping and design-controlled development, discussing when to start formal requirements work and how to keep your first version minimal yet complete.

Jeff emphasizes the importance of deeply fleshing out requirements before implementation—including error handling, which often comprises 70% of a product. We discuss tracer bullets as a development strategy, the value of writing test cases alongside requirements, and why tracking requirements completion gives you honest project status. Luca and Jeff also debate the finer points of MVPs versus prototypes, and Jeff announces his upcoming requirements management tool for medical device startups.

• [00:00] Introduction and listener feedback on Part 1
• [02:30] The prototyping phase: answering 'can we build it?' and 'should we build it?' before design controls
• [06:00] Luca vs. Jeff: The great MVP and prototype debate
• [12:00] Starting the V-model: minimal but deeply fleshed-out requirements for V1
• [18:00] Error handling is 70% of your product—don't skip it in requirements
• [22:00] When to write test cases: early, alongside requirements
• [26:00] War story: the SATCOM system that needed a satellite slot in five years
• [32:00] Project management: tracking requirements completion for honest status updates
• [38:00] Tracer bullets: vertical slices through all layers, not horizontal completion
• [45:00] Jeff's upcoming requirements and test management tool for medical device startups

"Error handling is 70% of your product, if not more. If you only do the 30% of the requirements for the happy path, you're fooling yourself." — Jeff

"If you don't get this right at the outset, it will haunt you through the entirety of your product development process." — Luca

"Paper is the best place to figure it out. Actually think through the requirements rigorously before you start building." — Jeff

• Agile Embedded Slack Channel - Community discussion space for embedded development topics
• Matt Pocock's YouTube Channel - AI for serious engineers, discusses tracer bullets and AI-assisted development
• The Pragmatic Programmer - Classic software development book, source of the tracer bullet concept
• The Art of Unix Programming by Eric S. Raymond - Referenced for the chapter 'Don't just do something. Stand there.'
• Embedded.fm Episode 440: Condemned to Being Perfect - Crossover episode with Elecia White and Christopher White, where bootloaders and update strategies came up
• Jeff's Requirements Management Tool - Upcoming requirements, risk, and test management tool for medical device startups

You can find Jeff at https://jeffgable.com.
You can find Luca at https://luca.engineer.

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Ryan Torvik and Luca have started the Embedded AI podcast, check it out at https://embeddedaipodcast.com/