Lessons learned: Refactoring as a means in the redesign of an OO knowledge engineering system

Applied to the redesign of a knowledge engineering system, refactoring was used as a principle means to achieve greater extendibility, maintainability, and stability. A postmortem analysis and a convergence analysis during a beta system test showed that refactoring techniques could be applied successfully. The benefits of applying refactoring techniques lies in presenting the existing functionality and reducing the entropy of the system by extending it in small steps. Carefully executed refactoring twists the law that entropy always increases. On the other hand, refactoring benefits do not come for free. Refactoring specifically implies that it must be done one step at a time. Tests should be executed after each step, Automated tests must be in place within a project to achieve the benefits of refactoring techniques. For automated testing, we successfully applied not only unit and regression tests, but assertion mechanisms.(1) In the December 2000 issue of the Journal of Object-ORiented Programming,(2) we presented same lessons learned by applying patterns as a guiding technology for system redesign, This article continues with the the lessons learned during the course of this redesign project.