 A typical place for an APIDS would be between a web server and the database management system, monitoring the SQL protocol specific to the middleware/business logic as it interacts with the database.At a basic level an APIDS would look for, and enforce, the correct (legal) use of the protocol.However at a more advanced level the APIDS can learn, be taught or even reduce what is often an infinite protocol set, to an acceptable understanding of the subset of that application protocol that is used by the application being monitored/protected.