MONITORING TEMPORAL PRECONDITIONS IN A BEHAVIOR-ORIENTED OBJECT MODEL

Modern database applications require advanced means for modelling syst em structure and dynamics. Temporal logic has been proven to be a suit able vehicle for specifying the possible evolution of objects to be st ored in databases. Past-directed temporal logic, as a means to describ e the influence of the historical evolution of a database on applicabl e state changes, is one facet for the specification of object behaviou r. The conceptual modelling language TROLL emphasizes the behaviour of objects over the course of time. Especially the restriction of events with preconditions in past-directed temporal logic has to be monitore d, when a system specified in TROLL is implemented or prototyped. In t his report we introduce a technique for monitoring (past-directed) tem poral preconditions during database runtime. This technique avoids sto ring the whole database history for evaluating temporal preconditions. Instead, little information about the database history is derived for specific temporal preconditions using transition graphs. This derived information is evaluated in later database states, when the temporal precondition is to be checked. We also describe a possible integrity m onitor able to check temporal preconditions during database runtime. S uch a monitor is specified locally to objects with advantages for dist ributed implementations. The dependency of the checking procedure on u pdate operations leads to an optimized monitoring process that makes a n efficient control of dynamic integrity constraints possible. The mon itoring process itself is specified with the language TROLL. An implem entation of an integrity monitor can therefore be tackled together wit h the language implementation. The advantages and future extensions of the proposed monitoring process and its modelling are briefly discuss ed.