Redesign of UML Class Diagrams: A Formal Approach Piotr Kosiuczenko Department of Computer Science University of Leicester, LE1 7RH, UK e-mail:
[email protected], tel: 0043 116 2522025 Regular Paper Abstract: Contracts provide a precise way of specifying object-oriented systems. When a class structure is modified, the corresponding contracts must be modified accordingly. This paper presents a method of transforming contracts, which allows the extension of a mapping defined on a few model elements, to - what we call - an interpretation function, and to use this function to automatically translate OCL-constraints. Interestingly, such functions preserve reasoning using prepositional calculi, resolution, equations, and induc- tion. Interpretation functions can be used to trace model elements throughout multiple redesigns of UML class diagrams in both the forward, and the backward direction. The applicability of our approach is demonstrated in several examples, including some of Fowler’s refactoring patterns. Keywords: UML, OCL, formal methods, refactoring, requirements tracing. 1 Introduction Object-oriented modelling languages provide textual, and diagrammatic means for system specification (cf. [UML05]). An object-oriented system and its real-world environment are modelled using abstractions such as class, association, generalization, operation, and prop- erty. Class diagrams specify a common structure, and relationships between objects; they are often detailed by constraints. System specification, design, and implementation occur in a series of steps. There exist different software engineering approaches which detail how those steps can be performed. In the 80’s, and early 90’s, the waterfall model prevailed in software engineering. In this process, one has to begin with fixed requirement specifica- tion, design the system, and then implement the design specification.