Today I read a post from Dan Linstedt titled "How Data Models can Impact Business." I followed the rather lengthy, but descriptive post, until I got to this part:
"Ok, I kind-of buy it, but what about Referential Integrity, when should that be enforced?
In two places:
1) When the data is captured within the application capturing it - it would clean up a LOT of these source systems, and put much more rigorous business logic (and cleaner data) into the source systems to begin with.
2) When the data is "released" for users, to reports, to screens, to output. This is when reusable common services / routines for getting data out are helpful. They implement the referential integrity in the application layer."
Now, I haven't been in IT all that long (5+ years now), but I put as much business logic into the database as I possibly can. I use the front end (APEX, woohoo!), to handle row color or something along those lines.
If you start with a good, flexible model, have a strong database team (DBAs, Developers) and you build a good API to your physical model (no INSERT, UPDATE or DELETE to any users, the only entry point to your tables being your API), flexibility and maintainability should not be a problem. Making changes should not entail a monumental effort. I suppose if the application in Mr. Linstedt's article is the only point of entry into the tables, I probably wouldn't really disagree (he's just moved it from my database API to his application), but then you have a giant bucket. Why not just use what you have paid for and build it in the database? That way, more than one application can use the same API over and over.