If effective knowledge-based support is to be provided for software designers, the process of software design, and the classes of knowledge used by designers must be understood more clearly. It has been shown that a software designer's experience of designing software in the current application domain has a significant effect on the production of a quality design. However, in gaining experience of designing software, a designer gains knowlegde in various distinct areas, including software design and the application domain. It is currently unclear which elements of this experience are important. In particular, the role of application domain knowledge that is independent of software design is of great significance for builders of intelligent software design support systems, since the overheads involved in providing application domains knowledge for a variety of application domains in such systems would be huge. This paper reports on a study that has been carried out to gain insights into this question, based around the structured techniques of DeMarco (1979) and Yourdon and Constantine (1979). From this preliminary investigation it would appear that a designer's general knowledge of the application domain does not affect the quality of a design produced for a system in this domain; this runs contrary to current popular beliefs.
