QVT Operational component is a partial implementation of the OMG standard specification (MOF) 2.0 Query/View/Transformation. In long term, it aims to provide a complete implementation of the operational part of the standard.
A high level overview of the QVT Operational language is available as a presentation from EclipseCon 2008, Model Transformation with Operational QVT.
Another high level overview of the QVT Operational language is available as a presentation from EclipseCon 2009, The Art of Model Transformation with Operational QVT.