Comment by airbreather

80% done, with no code.

This is often how a functional safety project works - specification is everything, no point writing any code until you know exactly what you plan to build.

Due to traceability requirements it becomes a very waterfall approach.

However one way of improving methodology and outcomes is an executable specification that can be converted to code and documenting at the very last minute, meaning you can be specifying right up until you need to deploy.

Executable specification concept comes from IEC 61499.