Automated refactoring to introduce design patterns

Software systems have to be flexible in order to cope with evolving requirements. However, since it is impossible to predict with certainty what future requirements will emerge, it is also impossible to know exactly what flexibility to build into a system. Design patterns are often used to provide this flexibility, so this question frequently reduces to whether or not to apply a given design pattern. We address this problem by developing a methodology for the construction of automated transformations that introduce design patterns. This enables a programmer to safely postpone the application of a design pattern until the flexibility it provides becomes necessary. Our approach deals with the issues of reuse of existing transformations, preservation of program behaviour and the application of the transformations to existing program code