ATL, the Atlas Transformation Language, is the ATLAS INRIA & LINA research group's answer to the OMG MOF/ QVT RFP. It is a model transformation language specified as both a metamodel and a textual concrete syntax. In the field of Model-Driven Engineering (MDE), ATL provides developers with a means to specify the way to produce a number of target models from a set of source models.

The ATL language is a hybrid of declarative and imperative programming. The preferred style of transformation writing is the declarative one: it enables to simply express mappings between the source and target model elements. However, ATL also provides imperative constructs in order to ease the specification of mappings that can hardly be expressed declaratively.

An ATL transformation program is composed of rules that define how source model elements are matched and navigated to create and initialize the elements of the target models. Besides basic model transformations, ATL defines an additional model querying facility that enables to specify requests onto models. ATL also allows code factorization through the definition of ATL libraries.

Developed over the Eclipse platform, the ATL Integrated Development Environment (IDE) provides a number of standard development tools (syntax highlighting, debugger, etc.) that aim to ease the design of ATL transformations. The ATL development environment also offers a number of additional facilities dedicated to models and metamodels handling. These features include a simple textual notation dedicated to the specification of metamodels, but also a number of standard bridges between common textual syntaxes and their corresponding model representations.