# Overview and Getting Started

For a quick demonstration of QVTc or QVTr editing and execution go to Getting Started.

A PDF version of this documentation is available at QVTd 0.14.0 Documentation.

## What is QVT?

The Query/View/Transformation language is the model transformation language specified by the OMG (Object Management Group). Or rather it is three specified languages to which Eclipse QVTd adds five intermediate languages.

- QVTo – Operation Mappings is an imperative transformation language supported by the Eclipse QVTo project.

- QVTr – Relations is a rich declarative transformation language.

- QVTc – Core is a simple core declarative transformation language.

QVTc and QVTr, generically referred to as QVTd, are supported the Eclipse QVTd project (QVT Declarative) and documented here.

The Eclipse QVTd support involves a transformation chain from QVTr via QVTc to executable form. The stages in this chain are:

- QVTu – a unidirectional declarative transformation language – a simplification of QVTc.

- QVTm – a minimal declarative transformation language – a further simplification of QVTc.

- QVTp – a partitioned declarative transformation language – a further simplification of QVTc.

- QVTs – a graphical declarative transformation language suitable for schedule determination.

- QVTi – an executable imperative transformation language – a variant of QVTc.

- Java – the ultimate executable form

Note that QVTu, QVTm, QVTp, QVTs and QVTi are not defined by the current OMG specification. It is possible that they may contribute to a future specification.

### Modeling Layers

- EMF is Modeled Structure

The Eclipse Modeling Framework ( EMF) supports the definition of structural meta-models and the subsequent use of models conforming to these meta-models. EMF also supports generating of Java code to represent the meta-models. Additional Java code can be provided to add behavior to the structural meta-models.

- OCL is EMF and Modeled Behavior

OCL provides a modeling language that allows the behavior to be embedded within the structural meta-models or provided as a complement to those meta-models. As a modeling language, OCL understands the models and so OCL code is much more compact than the equivalent Java. OCL code can be statically checked, whereas the corresponding Java code often uses reflection and so cannot be checked.

- QVT is Modeled Model Execution

Eclipse QVTd is an implementation of the OMG QVT 1.3 specification for use with Ecore and UML meta-models.

Eclipse QVTd exploits the extensibility of the Eclipse OCL Pivot model.