I generally agree about OO. It's good for small-to-medium-sized abstractions, but scales poorly compared to say an RDBMS. When your OO diagrams start to look li

I generally agree about OO. It's good for small-to-medium-sized abstractions, but scales poorly compared to say an RDBMS. When your OO diagrams start to look like ER diagrams, you are probably outside of OO's comfort zone. For large domain models, an RDBMS is superior to OOP in my opinion. OO is lousy at many-to-many relationships, for one, and lacks a visible identifier (primary key) to trouble-shoot data/state easily. OO may be helpful for modeling sub-sets of a domain model, but if you try to do the whole thing in an OO model, you'll either reinvent a database the hard way, turn grey, or do both.