Query/View/Transformation Operational Mapping Language - Eclipse Modeling Project: A Domain-Specific Language Toolkit - page 554

transformation uml2rdb( in uml:UML, out rdb:RDB)
extends BaseUml2Rdb
extends library UmlUtil
access library typeUtil;
At this time, M2M OML does not support access and extension of transfor-
mations and libraries. The M2M project does not yet have a Relations language
implementation, so it also does not yet support the refines keyword.
13.1.3 Intermediate Elements
OML supports the definition of intermediate classes and properties, which
can be helpful in some transformation definitions. Essentially, the definition of
an intermediate class and associated property allows for metamodel exten-
sion in the context of the transformation. The example used in the specification
follows; here, a LeafAttribute class is defined to help with mapping complex
type attributes to relational database columns. An intermediate property
allows for the storage of LeafAttributes in a Sequence , accessible as a fea-
ture of the Class element.
intermediate class LeafAttribute {
name : String;
kind : String;
attr : Attribute;
};
intermediate property Class::leafAttributes : Sequence(LeafAttribute);
Elsewhere in the transformation, the leafAttributes property can be
accessed in the same manner as any other feature of the metamodel. For example:
self.leafAttributes := self.attribute-> map attr2LeafAttrs();
Unfortunately, intermediate classes are not yet implemented in Eclipse M2M
OML. Intermediate properties are supported and can be a Tuple type, providing
somewhat of a workaround for the lack of intermediate classes, as shown next.
Another workaround is to define an intermediate class in a separate *.ecore
model and use it within the context of the transformation.
intermediate property UML::Class::leafAttributes :
Sequence ( Tuple (name: String , kind: String , attr :Attribute));