On the Role of Activity Diagrams in UML - A User Task Centered Development Process for UML

Activity Diagrams can be used to describe internal processing as well as action-object flow. Since they do not focus on events and object interaction, it is not clear, how to combine them with the typical object-oriented diagrams like class and statechart diagrams. In this paper we propose to use activity diagrams as a bridge between use case diagrams and class diagrams. This gives three benefits: a smooth transition from business processes to use cases, an abstract specification of complex object interactions and a succinct description of system functions affecting several objects. This use of activity diagrams is embedded in an overall software development process characterized by a focus on user tasks during analysis and incremental class diagram development.