This is simply incorrect. The real world has business logic, and that's ironclad (or should be, for a successful business, assuming you're not acquired at which point start the business data schema over). Where business logic has exceptions, those exceptions should be accommodated in the schema. But there should be no daylight between how the business works and how the schema records its every function. Anything else is bad design. It works for decades only if a business makes its decisions partially based on how those are constrained by prior logic, and the DNA of that logic is the schema.
In twenty years of "ERP Whispering" I've never known a "formal" "schema" (going to put "schema" in quotes here too, what that actually represents is a strictly validating structure, or system of any kind) that described a business object as utilized (process, reference, part number database) with anything greater than, say, forty percent commonality. At the high end. The remainder is waived, "ad-hocced", or is simply fibbed ("oh sure, all our parts have registered NSNs[1]").
The systems are, at their best, an executive class (VPs, Senior Mgmt) contracting a shaman/priestly class (me) to lay a sheet of order on throbbing chaos.
I probably should mention that it's possible - likely, even - that I have not worked for a non-dysfunctional business, and of course the ERP software ecosystem introduces its own peculiarities on top of that.
I realize I am badly abusing the word "schema" here. A lot of the time, we design schemas based on high level business requirements, and that's what I'm thinking about. There should be a LOT more between schema and business - a whole universe of business architecture, design, and software - but there never seems to be the money to do so.
In the wider context, though, the phenomenological world, I would posit, does not have business logic inherent in the fact of its own existence. This could get to be a very spatious, "dude-wheres-my-bong" sort of discussion, but I think the difference in Weltanschauung we're seeing here might be due to divergent experience.
It's almost certainly down to divergent experience. The shamaning and priesting I've done has almost exclusively begun with small companies that were working out their business operations at the same time as they were commissioning software. As they grow, the business logic evolves and the software had to grapple with that, but the originally unified logic imposes constraints both ways. The software sets limits on, and is in conversation with, the whims of management... if for no other reason than that 10 years in, on version 72, the cost of changing the data schema may outweigh the hoped-for advantage of some off the cuff idea to change fundamental operating practices. More concretely, e.g. if a custom logistics system grows up with a company from the ground floor, the business logic tends to bend around the software's limitations [clarification: Employees learn to get things done that weren't originally anticipated, in ways that weren't envisioned]; then the software slowly incorporates the new needs into formal features. If you're dealing with rational management (like the original founders) they will see the sense in maintaining logical continuity and tweak operations as needed to accommodate what should or shouldn't be done in software. [As opposed to "in operations". It's when employees are repeatedly writing on white boards or passing papers around for the same thing that it needs to be integrated as a feature]. But telling the management that "changing this fundamental aspect is impossible without significant downtime" is often enough to start the conversation of how to shape it so that the schema and the business remain in lock step.
This isn't perfect. Ask Southwest airlines, who grew with their own software until they couldn't, and then switched catastrophically to an entirely new system. Sometimes things reach a scale
of complexity that the software simply can't conform to. But a really good designer should see those things 2-3 years out and plan for them.
This is the real power of the shaman. I don't dictate business logic, but I do whisper when it contravenes the hard logic of the schema, I fight to minimize the number of exceptions ("hacks" of any kind) and through this keep the beast in check.
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.
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.
This is simply incorrect. The real world has business logic, and that's ironclad (or should be, for a successful business, assuming you're not acquired at which point start the business data schema over). Where business logic has exceptions, those exceptions should be accommodated in the schema. But there should be no daylight between how the business works and how the schema records its every function. Anything else is bad design. It works for decades only if a business makes its decisions partially based on how those are constrained by prior logic, and the DNA of that logic is the schema.