Query/View/Transformation Operational Mapping Language - Eclipse Modeling Project: A Domain-Specific Language Toolkit - page 551

one transformation, in which case the transformation declaration is terminated
by a semicolon. At the time of this writing, QVT Operational (QVTO) currently
supports only one transformation per file, so the previous syntax would result in
a compiler error. Instead, declare transformations as follows:

transformation uml2rdb( in uml:UML, out rdb:RDB);

Each model parameter is associated with an MOF extent. The transforma-
tion itself can be considered a class that is instantiated, causing the initialization
of the parameter extents. Output parameters are initialized to empty model
extents. All are accessible using the this variable, which refers to the transfor-
mation instance itself. When instantiating objects, the model extent can be
declared to remove ambiguity when multiple models of the same type are in use.
This is done using the @ sign followed by the name, as shown here:

transformation mindmap2requirements( in inModel : mindmap,

out oneModel : requirements, out outModel2 : requirements);

main () {
object Model@oneModel {
}

}

The modeltype declaration assigns an alias to a metamodel used in the con-
text of the transformation. The uses part of the declaration specifies the model
name and registered URI that the environment uses to resolve the MOF meta-
model definition. In the case of Eclipse QVT OML, MOF is equivalent to EMF's
Ecore metamodel. Therefore, URIs used here are those found in the NS URI field
of packages registered in EMF. To see a list of the models registered in the envi-
ronment, use the Metamodel Explorer view provided by the M2M OML com-
ponent. It's also possible to specify modeltypes using Eclipse platform:/
plugin and platform:/resource Uniform Resource Identifiers (URIs).
Note that it's not necessary to place the URI within parentheses following the
model name. The following is equivalent to our Unified Modeling Language
(UML) modeltype declaration earlier:

modeltype UML uses 'http://www.eclipse.org/examples/1.0.0/simpleuml';

You also can simply state the model name, which, in the case of M2M OML,
corresponds to the EMF registered package. This allows some flexibility because
several versions of a model could be registered in the environment, but it also can