Till AX 2012 R2, the Generate methods in DMF entity classes do not have attributes. These were identified by the field groups with names starting with Generate.
In AX 2012 R3, the Generate methods of entity classes need to have the Attributes mentioned so that they will be recognized in the Target entity mapping.
[DMFTargetTransformationAttribute(true),DMFTargetTransformationDescAttribute(<<Label for Descriotion>>),
And there is no need for us to create the field group with <<Generate method name>>.