UML design pattern metamodel-level constraints for the maintenance of software evolution

Pattern-based design, the use of design pattern during the design process, has become widely used in the object-oriented community because of the reuse benefits. However, design pattern defects can be injected in design maintenance phase because the changes of pattern-based design require the conformance not only to the change requirements but also to the corresponding design patterns. This process for conforming to the corresponding design patterns is an extra work for a maintainer as compared to traditional design maintenance, and also requires deep knowledge of design patterns. It is, therefore, crucial to maintain correct designs during design maintenance because defects introduced in design evolution may cause serious damage to software systems in later software development and maintenance. Hence, there is a need of a systematic design method for preventing design pattern defects being injected during pattern-based design maintenance so that the change results of pattern-based designs still conform to the corresponding design patterns. Conventional Unified Modeling Language (UML) design methods do not provide systematic ways of assessing pattern-based design conformance. Pattern Instance Changes with UML Profiles (PICUP) design method is developed as an improved design method for perfective and corrective UML pattern-based design maintenance and assessment. Design Pattern in UML Profiles (DPUP) is developed for formal specification of a design pattern. DPUPs are used for instantiation, maintenance, and assessment of UML pattern-based designs. DPUPs, as the main part of PICUP design method, provide metamodel-level UML design constraints using UML stereotype notations and metamodel-level Object Constraint Language (OCL) design constraints. In this research, assessments of pattern-based designs in UML class diagram with the corresponding DPUPs enforce maintainers to make correct changes of the designs. Pattern-related information is annotated in pattern-based design using stereotype notations and helps to assess pattern-based designs after changes. Furthermore, the structural conformance checking of a given UML pattern-based design can be automated by using the assessment tool. An explanatory two-case study is used to evaluate the effectiveness of PICUP design method with DPUPs. Questionnaire answers and pattern defect counts from the two-case study conducted by subject matter experts support the hypothesis that the PICUP method is an improved design method ensuring structural conformance of UML pattern-based designs to the corresponding design patterns during perfective and corrective design maintenance for software systems.