Profiles


Overview


The Profiles package contains mechanisms that allow metaclasses from existing metamodels to be extended to adapt them for different purposes. This includes the ability to tailor the UML metamodel for different platforms (such as J2EE or .NET) or domains (such as real-time or business process modeling). The profiles mechanism is consistent with the OMG Meta Object Facility (MOF).

Extensibility


The profiles mechanism is not a first-class extension mechanism, i.e., it does not allow for modifying existing metamodels. Rather, the intention of profiles is to give a straightforward mechanism for adapting an existing metamodel with constructs that are specific to a particular domain, platform, or method. Each such adaption is grouped in a profile.

It is not possible to take away any of the constraints that apply to a metamodel such as UML using a profile, but it is possible to add new constraints that are specific to the profile. The only other restrictions are those inherent in the profiles mechanism; there is nothing else that is intended to limit the way in which a metamodel is customized.

First-class extensibility is handled through MOF, where there are no restrictions on what you are allowed to do with a metamodel: you can add and remove metaclasses and relationships as you find necessary. Of course, it is then possible to impose methodology restrictions that you are not allowed to modify existing metamodels, but only extend them. In this case, the mechanisms for first-class extensibility and profiles start coalescing.

There are several reasons why you may want to customize a metamodel:

Profiles and Metamodels


There is no simple answer for when you should create a new metamodel and when you instead should create a new profile.