This week précis is not related to how developers use diagrams but to possible methods to evaluate notations according to their usability.
Green, T. R. G.: Cognitive dimensions of notations. In Proceedings of the Fifth Conference of the British Computer Society, Human-Computer interaction Specialist Group on People and Computers V (Univ. of Nottingham), pages 443 – 460. A. Sutcliffe and L. Macaulay, Eds. Cambridge University Press (1989).
Usability studies have been described in a significant number of papers, but the need for general methodologies persists. The author proposes the concept of cognitive dimensions as a partially conceived tool for evaluating in the context of programming languages how well a notation can assist its users.
Cognitive dimensions are defined as attributes that depict the structure in which information is presented. The principal examples of dimensions discussed in this paper are related to the visibility of dependencies, the resistance to local changes, the risk of premature commitments, the differentiation between roles, and the inability to avoid complex mental operations. However, this set of dimensions is not complete and should be refined taking into account the iterative and unpredictable order that governs the designing process.
Based on the characterization of object oriented languages through cognitive dimensions, the author concludes that these dimensions can be utilized to argue about practical problems. Moreover, he emphasizes that the environment supporting the notation must be taken into account.
This is an introductory paper that illustrates with examples the implications of particular features in programming language notations. Though the methodology behind cognitive dimensions is not clearly defined, the vocabulary presented is still in use.