OPSIS: a view mechanism for software processes which supports their evolution and reuse

The paper describes Opsis, a view mechanism applied to graph based process modelling languages of type Petri net. A view is a sub model which can be mechanistically constructed from another model by application of a perspective which: identifies all parts of the original model that are contained in the submodel; identifies and transforms all parts that constitute the interface to other sub models; adds new link relations to describe the behaviour of the sub model in interaction with the other sub models. Sub models are more easy to grasp and can be limited in scope to some well defined aspects of a global model, such as the view point ofa single role player. Composition of sub models is achieved through a merge operation on interface elements of sub models. The intended use of Opsis is: 1) process evolution-changes can be localised to certain views, which largely reduces the complexity of applying change; and 2) process reuse-libraries can contain reusable fragments of type view that can be combined using the composition operators.