Towards a Methodology Employing Critical Parameters to Deliver Performance Improvements in Interactive Systems

In the design of interactive systems, overall performance issues tend to receive less attention than provision of functionality. As a result, systems may not always offer performance improvements to their users. In this paper we present some proposals for methods based on the use of application-specific critical parameters, i.e., performance parameters that measure how well the system serves its purpose. We argue that these parameters can provide a basis for dealing with performance issues in design. To construct this basis, there is a need to focus on identifying parameters through field studies, and on constructing models for use in making performance predictions. We provide a number of examples of critical parameters, and discuss problems we have encountered in identifying them and in model construction. We summarise the results of a study of designers working with critical parameters. A final section of the paper discusses the feasibility of introducing critical parameters to HCI design practice.