Optimising OCL synthesized code

Abstract

OCL is a important element of many Model-Driven Engineering tools, used for different purposes like writing integrity constraints, as navigation language in model transformation languages or to define transformation specifications. There are refactorings approaches for manually written OCL code, but there is not any tool for the simplification of OCL expressions which have been automatically synthesized (e.g., by a repair system). These generated expressions tend to be complex and unreadable due to the nature of the generative process. However, to be useful this code should be as simple and resemble manually written code as much as possible. In this work we contribute a set of refactorings intended to optimise OCL expressions, notably covering cases likely to arise in generated OCL code. We also contribute the implementation of these refactorings, built as a generic transformation component using bentō, a transformation reuse tool for ATL, so that it is possible to specialise the component for any OCL variant based on Ecore. We describe the design and implementation of the component and evaluate it by simplifying a large amount of OCL expressions generated automatically showing promising results. Moreover, we derive implementations for ATL, EMF/OCL and SimpleOCL.