Engineering the Usability of a Visual Formalism for Real-time Temporal Logic

Abstract

Visual formalisms merge the rigor of mathematical notations with the naturality of graphic representation. This increases usability of formal methods, and may also improve their verification power through a richer involvement of the user. To achieve this goal, development of the visual representation must fulfill a twofold requirement: on the one hand, the design must capture the inherent rigor of the underlying formalism; on the other, it must meet the final user intuition.In this paper, we introduce, motivate and evaluate a visual formalism for a real-time logic. The visual formalism supporting presentation of the logic was designed by joining heuristic design and user-based evaluation. Heuristic principles were applied to define a limited set of visualization metaphors supporting consistent representation of basic semantic constructs. Alternative representations were defined where multiple choices were possible with no obvious expected preference. Heuristic assumptions were then refined and alternative representations were selected by resorting to the judgment of a representative sample of target end-users. The resulting notation was implemented within an interactive syntax-directed editor, which was then used to carry out a competitive user-based evaluation of the usability of textual and visual representations.