This article describes activity modeling as specified by the Systems Modeling Language (SysML) and the finalization of the Unified Modeling Language version 2 (UML 2). It reviews and updates an earlier proposed alignment between Enhanced Functional Flow Block Diagrams (EFFBD), UML 2 Activities, and requirements developed by the International Council on Systems Engineering and Object Management Group. It presents a spectrum of activity modeling techniques, ranging from a widely used systems engineering diagram, the EFFBD, to continuous flow modeling. The techniques include control capabilities, continuous system concepts, and others related to functional decomposition and allocation. The article also describes refinements of activity modeling concepts identified during SysML development.
activity model, functional flow, SysML, systems engineering, UML