A Two-level Calculus for Composing Hybrid QVT Transformations
The standard for model transformations QVT offers two dialects: Relations Language andOperational Mappings Language. Each one of these dialects can be used in isolation, resulting inpurely declarative transformations or purely imperative transformation respectively; alternatively, bothdialects can be combined resulting in a hybrid transformation approach. On the other hand, theavailability of compositional approaches to produce complex transformations from smaller units is amajor concern in the area of model transformations. Compositional approaches for pure QVTtransformations are supported by a number of tools; however no composition technique exists that canconsistently manage the hybrid approach. Such partial techniques provide suitable answers to mostpractical needs; but they do not cover the entire composition spectrum. The aim of this article is todescribe a technique for composing model transformations embracing both dimensions - declarativeand imperative - so that the hybrid approach can be smoothly supported. Additionally, we report theimplementation of a software tool supporting such technique and we sketch its validation.