Thus, deciding which strategy to apply cannot be pre-determined because it depends on the intermediate results. This implies that finding a general purpose strategy is difficult. The existence of more than one possible solution implies a need for different ways of reaching a goal. In general, studies of practice show that designer strategies are open-ended, intuitive and based on heuristics. Most studies conclude that deviations are the consequence of the ill-structured nature of design problems and include suspension of judgement and reformulation.
Decomposition is a commonly observed strategy usually in conjunction with others.
Other strategies observed were hill climbing, focusing on main functions or problems, combination of generate and test, generate and improve, deductive thinking, means-end analysis and low 'cognitive cost' strategy. Different types of solutions and knowledge require integration of different ways of representation and, therefore, of reasoning. Research into design practice is not being incorporated into knowledge-based system building in a sufficently coherent manner. Techniques are required for integration of different AI techniques with each other and conventional systems. A variety of tools is needed to support the designer's many different tasks.