Shazia W. Sadiq
PhD Thesis, 2002
 

Workflow systems are currently the leading technology for business process automation. Organizations seek to achieve higher goals in an exceedingly dynamic and competitive business environment by effective process management. Although workflow technology has been traditionally used for processes that exhibit characteristics of predictability and repetitiveness, it is evident that in current business environments, such process stability is highly doubtful. Change is present in some degree and form in almost all domains. Handling dynamically changing workflows is a highly complex issue. In many applications either the process logic cannot be completely anticipated, or it is subject to frequent change. Uncontrolled changes to the process model, or instances, can lead to serious erroneous and inconsistent states of the workflow. Several issues of modelling, verification, compliance and enactment arise.

Although workflow technology is fast growing on both the commercial as well as research fronts, to the best of our knowledge, no comprehensive solution for the handling of change exists as yet.  In this thesis we investigate this highly applied, yet complex issue. We approach the problem in a step by step manner, beginning with a taxonomy of change characteristics that allows us to classify the area into more precise and specialized problems. We call these dimensions of change and identify three dimensions, namely dynamism, adaptability and flexibility.

Dynamism: The first dimension represents dynamism - which is the ability of the workflow process to change when the business process evolves. This evolution may be slight as for process improvements, or drastic as for process innovation or process reengineering. In any case, the assumption is that the workflow processes have pre-defined models, and business process change, causes these models to be changed.  The biggest problem here is the handling of active workflow instances, which were initiated in the old model, but need to comply now with the new specification. The issue of compliance is rather a serious issue, since potentially thousands of active instances may be affected by a given process change. Achieving compliance for these affected instances may involve loss of work and therefore has to be carefully planned [SMO00]. A typical example of dynamic workflows can be found in university admissions. Consider a scenario of a large tertiary institute that processes thousands of admission applications every year. The procedure for application, review and acceptance is generally well defined and understood. Suppose that the office of postgraduate studies revises the admission procedure for postgraduate students, requiring all applicants to submit a statement of purpose together with their application for admission. To implement this change, there can be two options available; one is to flush all existing applications, and apply the change to new applications only. Thus all existing applications will continue to be processed according to the old process model. This requires the underlying workflow system to at least provide some version management support. The second, more challenging option to implement the change is to migrate to the new process. It may be decided that all applicants, existing and new, will be affected by the change. Thus all admission applications, which were initiated under the old rules, now have to migrate to the new process. This migration may involve addition of some transition workflow activities as well as rollback activities. Defining the migration strategy is a complex problem and has been the target of extensive research [Sad00a].

Adaptability: The second dimension of change is adaptability - which is the ability of the workflow processes to react to exceptional circumstances. These exceptional circumstances may or may not be foreseen, and generally would affect one or a few instances. Of course the handling of exceptions, which cannot be anticipated, is more complex. However, a large majority of exceptions can be anticipated and by capturing these exceptions, the adaptability of the workflow is promoted [Sad00b]. In fact, unless these exceptions are captured within the workflow model, their handling will continue to be done outside of the system, in the form of "system workarounds", the consequences of which may come in conflict with process goals. However the complete set of exceptions for a given process can never be captured, thus dealing with unanticipated (true) exceptions will always be an issue. Using the same example as before, we can consider dealing with an admission application for a student with a multi-disciplinary background. For example, a student with a background in microbiology may be applying for a degree in IT. The review of this application may require the services of an academic outside the offering department. This may be rare but, if captured within the process model, could be handled within the workflow system. Another example, which represents a true (unanticipated) exception, can be found in the employment workflow. An employment instance may have reached a stage where even the letter of intent has been issued. If at that time the organization issues a spending freeze, the active instances of the employment workflow will have to be dealt with, requiring rollback and/or compensation activities, even though the original employment workflow remains unchanged.

Flexibility: The third dimension is flexibility - which is the ability of the workflow process to execute on the basis of a loosely, or partially specified model, where the full specification of the model is made at runtime, and may be unique to each instance. Processes which depend on the presence of such flexibility for the satisfactory attainment of process goals can be found in many applications: A typical example of flexibility is healthcare, where patient admission procedures are predictable and repetitive, however, in-patient treatments are prescribed uniquely for each case, but none-the-less have to be coordinated and controlled. Another application is higher education, where students with diverse learning needs and styles are working towards a common goal (degree). Study paths taken by each student need to remain flexible to a large extent, at the same time providing study guidelines and enforcing course level constraints is necessary to ensure a certain quality of learning. Web content management is also characterized by flexible processes, where especially in large projects, every development suggests the need for an overall plan to provide the objectives, approvals, and strategy, as well as a flexible means of coordinating the combined efforts of the theme designers, graphic experts, programmers, and project planners. Effective Customer Relationship Management (CRM), a critical component in enterprise solutions, also signifies the need to provide a flexible means of composing call centre activities according to the available resources and data, by integrating CRM systems with core organizational workflow processes and underlying applications. The key issue in flexible workflows is the modelling of the loose or partial workflow. Thus rather than enforcing control through a rigid, or highly prescriptive model that attempts to capture every step and every option within the process, the model is defined in a more relaxed or "flexible" manner, that allows individual instances to determine their own (unique) processes. How to achieve such an approach to modelling is a significant challenge and has been addressed in [SSO01]

We then approach each dimension individually and give several insights into the issues involved, as well as propose methods for overcoming identified problems. We also identify a commonality between the dimensions and have devised a generic change methodology, as well as system requirements to facilitate the methodology. More details on proposed methods and the unified framework can be found in related publications