Despite the availability of a host of software design notations and associated tools, software developers are known to frequently turn to the whiteboard when faced with a specific design problem. There, they typically engage in an informal form of software design that relies heavily on sketching. However, whereas whiteboards afford flexibility and fluidity, they at the same time limit a designer in only being able to draw and erase content. This paper presents Calico, a novel software design tool that leverages electronic whiteboards to enhance the design experience with explicit support for the creative, exploratory aspects of design. Specifically, Calico offers a grid, scraps, and a palette together with gesturebased input to address several natural behaviors exhibited by software designers, including frequent shifts in focus, use of lowdetail models, and use of a mix of notations. To evaluate Calico, we performed a laboratory experiment involving eight pairs of graduate students and collected and analyzed six corporate design sessions that employed Calico. Results are promising and indicate the benefits of Calico, while they at the same time highlight several ways in which it can be enhanced.

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