Formulating the design rationale of visual representation

When designing a representation, a designer implicitly formulates a method required to understand and use the representation effectively. This paper aims at making the method explicit, in order to help designers elicit their design choices. In particular, we present a set of concepts to systematically analyze what a user must theoretically do visually to find information. The analysis consists in a decomposition of the activity of scanning into elementary visualization operations. We show how the analysis applies on various existing representation, and how expected benefits can be expressed in terms of elementary operations. The decomposition highlights the challenges encountered by a user when figuring out a representation, and helps designer to exhibit possible flaws in their design.The set of elementary operations form the basis of a shared, common language for representation designers.