We describe a Unified Modelling Language (UML) diagramming tool that uses an E-whiteboard, pen-based sketching interface to support collaborative design. Our tool allows designers to sketch UML visual modelling language constructs, mixing different UML diagram components, free-hand annotations and hand-written text. A key novelty of our approach is the preservation of handdrawn diagrams and support for manipulation of the diagrams using pen-based actions. UML sketches can be “formalized ” to computer-recognised and drawn diagrams, and exported to a 3 rd party CASE tool. 1.

Software engineers often use hand-drawn diagrams as preliminary design artefacts and as annotations during reviews. We describe the addition of sketching support to a domain-specific visual language meta-tool enabling a wide range of diagram-based design tools to leverage this human-centric interaction support. Our approach allows visual design tools generated from high-level specifications to incorporate a range of sketching-based functionality including both eager and lazy recognition, moving from sketch to formalized content and back, and using sketches for secondary annotation and collaborative design review. We illustrate the use of our sketching extension for an example domain-specific visual design tool and describe the architecture and implementation of the extension as a plug-in for our Eclipse-based meta-tool. 1.

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. Keywords: sketch-based user interfaces, E-whiteboards, CASE tools, unified modelling language, hand-drawn visual language recognition