[kqr]

I don't know what you mean by business logic but the (in my view successful) businesses I have seen operate more on the highly variable whim of upper management than any sort of ironclad logic.

You notice this quickly when you computerise existing human processes. They are riddled with (sometimes very valuable!) inconsistencies that are hard to fit into the regular computer mold some designer thought was sensible.

[noduerme]

I responded at length to the sibling but just want to say - usually where I've come in there is an operations manual that works very much like a schema. Investigating where it's being overridden in daily practice often helps to form more linear processes / more consistent logic than was in the manuals. Once those are worked out, the software becomes the glue that forces employees to follow the processes, and the manual is about the software. But you're right: Stepping into a messy organic system and writing software around it is hard. It's much harder if they aren't willing to be flexible.