DT: The author of the following quote resists the idea that a primary function of an RDBMS is indeed to manage the meaning of the data, through constraints.
If we step back and look at what RDBMS is, we’ll no doubt be able to conclude that, as its name suggests (i.e. Relational Database Management System), it is a system that specializes in managing the data in a relational fashion. Nothing more. Folks, it’s important to keep in mind that it manages the data, not the MEANING of the data! And if you really need a parallel, RDBMS is much more akin to a word processor than to an operating system. ...Why should we tolerate RDBMS opinions on our data? We’re the masters, RDBMS is the servant, it should shut up and serve. End of discussion.