NexusDB

NexusDB has an internal event infrastructure that you can hook into by means of Monitors and Extenders. Monitors/Extenders allow changes to the default behaviour of database events.  These internal events are fired on particular changes or conditions that occur within NexusDB's core engine.  These events work very much like triggers.  Since Monitors/Extenders are integrated into the core database engine, they are actually much more powerful than traditional SQL based triggers.

Monitors and extenders always work together.  Monitors get notified on creation of internal server objects such as sessions, databases, cursors, etc..  When the server creates these objects, a monitor can attach extenders to these objects.  Extenders handle specific events that occur within these objects (e.g. the posting of a record in a Cursor object) and can stop, change or extend the default behaviour (e.g. disallowing post for certain users).

Monitors and Extenders can be used for many purposes: logging, custom change notification systems, referential integrity and more.   NexusDB includes a functional implementation of referential integrity based on using monitors and extenders.  The event mechanism within NexusDB is extensive and complete; Monitors and Extenders empower you to exploit this mechanism.