SUMLOW: early design-stage sketching of UML diagrams on an E-whiteboard

Most visual diagramming tools provide point-and-click construction of computer-drawn diagram elements using a conventional desktop computer and mouse. SUMLOW is a Unified Modelling Language (UML) diagramming tool that uses an E-whiteboard and sketching-based user interface to support collaborative software design. SUMLOW allows designers to sketch UML constructs, mixing different UML diagram elements, diagram annotations and hand-drawn text. A key novelty of the tool is the preservation of hand-drawn diagrams and support for manipulation of these sketches using pen-based actions. Sketched diagrams can be automatically "formalized" into computer-recognised and drawn UML diagrams and then exported to a 3rd party CASE tool for further extension and use. We describe the motivation for SUMLOW, illustrate use of the tool to sketch various UML diagram types, describe its key architecture abstractions and implementation approaches, and report on two evaluations of the toolset. We hope our experiences will be useful for others developing sketching-based design tools or those looking to leverage pen-based interfaces in software applications.