[kevan]

>when we move to a new system we don’t get the actual business logic. we just reverse engineer it from the data.

I'm pretty sure this happens in most fields that don't spec out absolutely everything in advance. In an ecommerce setting my team had to do this with the checkout logic because the old system was so complex and convoluted. Starting with a fork of a 3rd party platform and then unleashing 10 years of short-term contractor enhancements basically guarantees that no one will have full specs.

[denimnerd]

well my team builds the software to please regulators so all the original specs were signed off by legal and regulators. the next generation of each project simply fork lifts that data and massages the logic until it matches up