Although workflow management systems are most applicable when an organization follows standard business processes and routines, any of these processes faces the need for handling exceptions, i.e., asynchronous and anomalous situations that fall outside the normal control flow.In this paper we concentrate upon anomalous situtations that, although unusual, are part of the semantics of workflow applications, and should be specified and monitored coherently; in most real-life applications, such exceptions affect a significant fraction of workflow cases. However, very few workflow management systems are integrated with a highly expressive language for specifying this kind of exception and with a system component capable of handling it. We present Chimera-Exc, a language for the specification of exceptions for workflows based on detached active rules, and then describe the architecture of a system, called FAR, that implements Chimera-Exc and integrates it with a commercial workflow management system and database server. We discuss the main issues that were solved by our implementation, and report on the performance of FAR. We also discuss design criteria for exceptions in light of the formal properties of their execution. Finally, we focus on the portability of FAR on its unbundling to a generic architecture with detached active rules.

Specification and implementation of exceptions in workflow management systems

This paper presents a classification framework for workflow exception handling in the form of patterns. This framework is independent of specific modelling approaches or technologies and as such provides an objective means of delineating the exception-handling capabilities of specific workflow systems. It is subsequently used to assess the level of exceptions support provided by eight commercial workflow systems and business process modelling and execution languages. On the basis of these investigations, we propose a graphical, tool-independent language for defining exception handling strategies in workflows.

Workflow exception patterns

Many organizations use information technology to support various aspects of their business processes: the operational aspect, collaboration between employees, etc Workow management systems aim at supporting the operational aspect of complex business processes by using process models to automate the ordering of activities (ie, ow of work) The term `support' here relates to the ability of workow management systems to control the execution of business processes Contemporary workow management systems lack exibility, ie, the system controls in detail how employees should execute business processes While work- ow management systems deal well with predictable business processes, they are not able to handle unforeseen situations, which occur often in real-life business processes Although employees mostly have the knowledge and experience that enables them to deal with exceptional situations, they are not able to apply the right action because the system enforces the standard procedure of work This often has various undesired consequences: work is done `outside' the system, work cannot be done in the appropriate way, dissatisfaction of employees, resistance towards the system, etc As a result, workow management systems cannot be used properly if it is necessary that employees control the execution of business processes This thesis proposes a new approach to workow management systems that can facilitate contemporary business processes in a better way by enabling a better balance between exibility and support As opposed to traditional approaches which use procedural process models to explicitly (ie, step-by-step) specify the execution procedure, the proposed approach aims at the specification of business processes using constraints, ie, processes are modeled by rules that should be followed while executing business processes Constraint-based models implicitly specify the execution procedure by means of constraints: any execution that does not violate constraints is possible In addition to proposing a constrainbased approach, a concrete language for specification of constraints is given and the proof-of-concept prototype declare is described On the one hand, constraint-based management systems are exible, which allows employees to deal with specific (e/g/ unpredicted) situations in the most adequate way On the other hand, constraint-based management systems can support employees when it comes to aspects of business processes that are too complex for humans to handle There are several ways in which constraintbased management systems can provide both exibility and support

Constraint-based workflow management systems : shifting control to users

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This paper presents the realisation, using a Service Oriented Architecture, of an approach for dynamic, flexible and extensible exception handling in workflows, based not on proprietary frameworks, but on accepted ideas of how people actually work. The resultant service implements a detailed taxonomy of workflow exception patterns to provide an extensible repertoire of self-contained exception-handling processes called exlets, which may be applied at the task, case or specification levels. When an exception occurs at runtime, an exlet is dynamically selected from the repertoire depending on the context of the exception and of the particular work instance. Both expected and unexpected exceptions are catered for in real time, so that 'manual handling' is avoided.

Dynamic, Extensible and Context-Aware Exception Handling for Workflows

Workflow Management Systems are becoming more and more important to organizations for the execution of business processes. However, most current systems lack a consistent way of dealing with failures and exceptions. This paper proposes to use an exception-handling mechanism to provide ‘transactional’ features for workflow management systems. The modeler specifies exception handlers for activities to deal with exceptions. These exception handlers change the workflow that is being executed to deal with exceptions as they arise. Based on this idea we discuss which exceptions and exception handlers should be supported and how they interact to provide transactional capabilities.

van R. Stiphout

Papers

TREX, workflow TRansaction by means of EXceptions