What Makes a Good Diagram? Improving the Cognitive Effectiveness of Diagrams in IS Development

Diagrams play a critical role in IS development. Despite this, ISD practitioners receive little or no instruction on how to produce “good” diagrams. In the absence of this, they are forced to rely on their intuition and experience, and make layout decisions that distort information or convey unintended meanings. The design of ISD graphical notations is

ad hoc

and unscientific: choice of conventions is based on personal taste rather than scientific evidence. Also, existing notations use a very limited graphic vocabulary and thus fail to exploit the potential communication power of diagrams. This paper describes a set of principles for producing “good” diagrams, which are defined as diagrams that communicate effectively. These provide practical guidance for both designers and users of ISD diagramming notations and are soundly based on theoretical and empirical evidence from a wide range of disciplines. We conclude that radical change is required to ISD diagramming practices to achieve effective user-developer communication.