A well engineered data model can also be used as the basis for a business rules engine. This is popular in enterprise environments that use technology like oracle db or mssql. It is possible to implement all the core business logic as stored procedures and functions. These can be directly invoked from something like a web server. Instead of putting all the session validation logic in backend code, it could live in PL/SQL, T-SQL, etc.

The benefit to having the logic and the data combined like this is difficult to overstate. It makes working in complex environments much easier. For example, instead of 10 different web apps each implementing their own session validation logic in some kind of SSO arrangement, we could have them call a procedure on the sql box. Everyone would then be using the same centralized business logic for session validation. Any bugs with the implementation can be fixed in real time without rebuilding any of the downstream consumers.