Understanding a problem domain is a fundamental prerequisite for good software design. In object-oriented systems design, modeling is the fundamental first phase that focuses on identifying core concepts and their relations. How to properly support modeling is still an open problem, and existing approaches and tools can be very different in nature. On the one hand, lightweight ones, such as pen & paper/whiteboard or CRC cards, are informal and support well the creative aspects of modeling, but produce artifacts that are difficult to store, process and reuse as documentation. On the other hand, more constrained and semi-formal ones, like UML, produce storable and processable structured artifacts with defined semantics, but this comes at the expense of creativity. We believe there exists a middle ground to investigate that maximizes the good of both worlds, that is, by supporting software modeling closer to its essence, with minimal constraints on the developer's creativity and still producing reusable structured artifacts. We also claim that modeling can be best treated by using the emerging technology of touch-based tablets. We present a novel gesture-based modeling approach based on a minimal set of constructs, and CEL, an iPad application, for rapidly creating, manipulating, and storing language agnostic object-oriented software models, which can be exported as skeleton source code in any language of choice. We assess our approach through a controlled qualitative study.

The design of object-oriented systems starts with modeling, a process to identify core concepts and their relations. Mainstream modeling techniques can be either informal (white board, CRC cards, etc.) or formal (e.g., UML editors). The former support well the creative modeling process, but their output is difficult to store, process and maintain. The latter reduce these problems, at the expense of creativity and productivity because they are tedious and not trivial to use. We present Cel, a touch- and gesture-based iPad application to rapidly create, manipulate, and store language agnostic object-oriented software models, based on a minimal set of constructs. Demo video URL: http://youtu.be/icQVS6w0jTE.