Ode as an Active Database: Constraints and Triggers

The Ode object-oriented database provides facilities for associating constraints and triggers with objects.Constraints and triggers are associated with class (object type) definitions which makes them easy to read,to implement, and to blend with object inheritance. In this paper, we state our design goals in providingtrigger and constraint facilities for an object-oriented database, describe the constraint and trigger facilitiesin Ode, their implementation, and illustrate their use. Although triggers and constraints can beimplemented by similar mechanisms, we point out the significant conceptual differences. Further, wedistinguish between integrity constraints that must be maintained on a transaction basis and those that areinherent to an object and are more appropriately maintained on an object update basis. We also discussrelated issues such as intra-object versus inter-object constraints and triggers, coupling modes, order andenvironment of invocation.