What makes software design effective?

Software design is a complex cognitive process in which decision making plays a major role, but our understanding of how decisions are made is limited, especially with regards to reasoning with design problems and formulation of design solutions. In this research, we have observed software designers at work and have analysed how they make decisions during design. We report on how factors such as design planning, design context switching, problem-solution co-evolution and the application of reasoning techniques influence software design effectiveness.