Software Quality in User Centred Design

The paper describes a practical experience of measuring and modelling software quality using a development process based on the User-Centred Design approach. A crucial aspect of this approach is related to the evolution of the developed system due to the iterative design process. The experiment concerns of designing and evaluating prototypes for a train traffic control system for the Italian National Railways (FS). The paper points out the critical issues in a measurement practice starting from the early phases of the project. The description of the quality model for the project is presented. Moreover, the criteria identified to select the metrics and the metrics used are described together with the problems encountered in relation with this specific design approach. The paper points out the need for more suitable and powerful metrics and suggests in which direction the metrics should be up-dated. The reported experience shows that use of similar metric sets should be encouraged, but comparison of measurement values must be limited to projects with similar characteristics.