The untrained eye : what makes a representation easy for novice readers to understand?

It is generally recognised that choice of notations can have a significant effect on the system development process, particularly in the early stages of requirements capture and validation. In the development of interactive systems it is essential that stakeholders are able to understand representations of key design ideas, in order that they can participate meaningfully in the development process. Although in some development projects this requirement is fulfilled by an early prototype, there are many situations in which paper-based representations have to be used. Some stakeholders, such as clients and potential users of the system, may be unfamiliar with the notations used by software engineers and therefore find it difficult to understand representations produced using such notations well enough to contribute effectively to system development. In this paper we discuss the problem of how to choose the most effective notation in a particular situation and identify understandability of representations as a key issue for interactive development. We then consider ways in which the notion of understandability may be defined in this context, and discuss the possibility of evaluating notations in terms of ease of understanding.