A model captures a view of a physical system. It is an abstraction of the physical system, with a certain purpose.

This purpose determines what is to be included in the model and what is irrelevant. Thus the model completely describes those aspects of the physical system that are relevant to the purpose of the model, at the appropriate level of detail.

A package is used to group elements, and provides a namespace for the grouped elements.

A package can have one or more profile applications to indicate which profiles have been applied.

A profile defines limited extensions to a reference metamodel with the purpose of adapting the metamodel to a specific platform or domain.