Exception handling in an object-oriented workflow management system

Abstract

Workflow is automation of a business process. A Workflow Management System (WFMS) is a system that assists in defining, managing and executing workflows. Most of the current WFMSs are built on traditional relational database systems and/or are using an object-oriented database system for storing the definition and run time data about the workflows. However, a WFMS requires advanced modelling functionality to support adaptive features, such as on-line exception handling. An exception is an event (i.e., something that happens), which deviates from normal behaviour or may prevent forward progress of a workflow. Indeed, exception handling in WFMSs is a very important problem since it is not possible to specify all possible outcomes and alternatives. This problem is very challenging mainly because of the various inter-dependencies among activities, run-time data, agents executing these activities, and semantics attached to these entities. Thus, an effective approach to exception handling is to employ a multi-faceted solution, which can integrate and facilitate an implementable solution. Effective reuse of existing exception handlers can greatly help in dealing with workflow exceptions, and reduce the burden on the workflow designer when designing these exception handlers. On the other hand, system-assisted support for user-driven resolution of unexpected exceptions and workflow evolution at run-time is vital for an adaptive WFMS. This thesis describes ADOME-WFMS, a comprehensive framework in which the problem of workflow exception handling can be adequately addressed. It uses an advanced meta-modelling approach using various enabling technologies (such as object orientation, roles, rules, and active capabilities) supported by an integrated environment, the ADOME (Advanced Objected Modelling Environment). The resultant system (viz., ADOME-WFMS) embodies a flexible, objected-oriented WFMS supporting dynamic match making, migrating workflows and exception handling. Then, an adaptive exception manager and its web-based interface for ADOME-WFMS are presented with procedures for supporting the following: reuse of exception handlers, thorough and automated resolution of expected exceptions, effective management of Problem Solving Agents, system-assisted exception handling, user-driven computer supported resolution of unexpected exceptions, workflow evolution, and exception driven workflow recovery. Finally, this flexible WFMS is extended to support E-services to illustrate its applicability within an emerging application domain.