From a passive to an active database supporting exceptions

Abstract

This paper presents a mechanism to enforce consistency in object oriented DBMS using pre-conditions and post-conditions on methods. This mechanism is coupled with an exception mechanism to allow deferred controls and semantic tolerance. Conditions are defined using SQL-like expressions and methods composition. Exceptions are defined at the class level. We consider that an exception has a signature (the context of the exception) and an implementation (the process associated with the exception). We define the semantics of inheritance related to exceptions. The process control of this exception mechanism is also presented. This model can be considered at an execution level and we show how some general integrity rules (e.g referential integrity) can be compiled into pre(post)-conditions and exceptions.