UML Model Refactoring as Refinement: A Coalgebraic Perspective

Although increasingly popular, Model Driven Architecture (MDA)still lacks suitable formal foundations on top of which rigorousmethodologies for the description, analysis and transformation ofmodels could be built. This paper aims to contribute in thisdirection: building on previous work by the authors on coalgebraicrefinement for software components and architectures, it discussesrefactoring of models within a coalgebraic semantic framework. Architectures are defined through aggregation based on a coalgebraic semantics for (subsets of)UML. On the other hand, such aggregations, no matter how large and complex they are, can always be dealt with ascoalgebras themselves. This paves the way to a discipline ofmodels´ transformations which, being invariant under either behavioural equivalenceor refinement, are able to formally capture a large number of refactoring patterns. The main ideas underlying this research are presented through a detailed example in the context of refactoring of UML class diagrams.