Abstract
In a general study of the literature eleven main areas of research were considered relevant to workflow management and its application in the domain of Sales Order Processing (SOP). It was concluded that exception handling may provide a unifying focus on the dynamic behaviour of workflow systems. Indeed this initial study revealed that current workflow approaches: 1. will overly constrain sales order processors as they seek to handle exceptions by imposing 'Generate Works Order'. unrealistic and thus rigid ways of working onto their end-users. 2. do not support the needs of workflow system developers very well, since their workflow specifications are time-consuming to develop and maintain and are difficult to verify. Having made these observations this study conducted a detailed literature study and identified three main classes of workflow approaches, namely: traditional workflow approaches (i.e. SADTIIDEFO, Grai Nets, IDEF3, IEM and ClMOSA), ECA workflow approaches (i.e. WIDE and Rapide) and transactional workflow approaches (i.e. Sagas, ConTracts, and Partial Rollbacks). Subsequently it was decided to study specific properties of sales order processing exceptions and their effects. Having established the basic nature of a new model of exceptions in sales order processing domains, it was found to be possible to reason about the way activities should be synchronised in the presence of exceptions, and to define a set of requirements for sales order processors. Also workflow system developer requirements were defined. In the next phase it was concluded that workflow approaches that handle exceptions (i) by executing predefined sequences of compensation activities (such as traditional and ECA workflow approaches do) do support some of the sales order processor requirements needed, but only meet a few of the developer requirements, and (ii) by dynamically generating compensation activities from some base of exception handling knowledge (as implemented by transactional workflow approaches) cannot support many realistic application scenarios, but that relatively their specifications take little to time to develop, are easy to maintain and are simple to check. A new workflow approach was proposed based on (i) the concept of deploying both standard and exception workflows and (ii) a new definition of workflow 'state' and 'transformation': Whilst a standard workflow captures the state of a workflow based on the assumption that no exception has occurred, exception workflows capture different states of a workflow for exceptions that have occurred. A rule set defines transformations between these workflows. Also a new implementation approach was proposed based on a workflow engine, agent and application components. Finally in a case study the proposed workflow approach and reviewed workflow approaches were compared with each other. It was observed that the proposed workflow approach can support more realistic application scenarios and meets many of the workflow system developer requirements.
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