Organizing long-running activities with triggers and transactions

This paper addresses the problem of organising and controlling activities that involve multiple steps of processing and that typically are of long duration. We explore the use of triggers and transactions to specify and organize such long-running activities. Triggers offer data- or event-driven specification of control flow, and thus provide a flexible and modular framework with which the control structures of the activities can be extended or modified. We describe a model based on event-condition-action rules and coupling modes. The execution of these rules is governed by an extended nested transaction model. Through a detailed example, we illustrate the utility of the various features of the model for chaining related steps without sacrificing concurrency, for enforcing integrity constraints, and for providing flexible failure and exception handling.