Regarding the specifications here: http://www.omg.org/technology/documents/formal/uml.htm
What is the difference btn without and with change bars?
As for "superstructure and infrastructure", I found out the following: "The UML infrastructure specification defines the foundational language constructs required for UML 2.1.2. It is complemented by UML Superstructure, which defines the user level constructs required for UML 2.1.2. The two complementary specifications constitute a complete specification for the UML 2 modeling language."
Where do I look into if I want to know the UML metamodel in order to know how to map a language construct into a UML model?
Thank you!