Recognising Sketches of Euler Diagrams Augmented with Graphs

Euler diagrams form the basis of many visual languages. Such languages are formed by augmenting Euler diagrams with graphs or shading. However, tool support for creating augmented Euler diagrams is generally limited to generic diagram editing software using mouse and keyboard interaction. A more natural and convenient mode of entry is via a sketching interface which facilitates greater cognitive focus on the task of diagram creation. Previous work has developed sketching interfaces for Euler diagrams. This paper presents the first sketch tool for Euler diagrams augmented with graphs and shading. The tool allows the creation of sketches of these diagrams via pen-based interaction. To effect the recognition process, we define heuristics for classifying strokes as either curve, node, edge, or shading. To evaluate our recognition engine, we asked 10 participants to each sketch six augmented Euler diagrams. Using the results of the study, we fine-tuned the recognizer, achieving a statistically significant improvement.