UML is a language that has different pieces to it, for example, classes and associations, etc Those pieces basically provide a describition of a system and therefore you could have a UML description of the UML. That UML portrayal of UML is known as the UML meta model.
This empowers a designer to broaden the UML metal model by adding new kinds of symbols, icons and special labels to particular elements in the model in what's known as a Profile diagram. Profile diagram is structure diagram which describes lightweight extension mechanism to the UML by defining custom stereotypes, tagged values, and constraints. Profiles allow adaptation of the UML metamodel for different:
- Platforms, such as Java EE or Microsoft .NET Framework, or
- Domains, such business process modeling, service-oriented architecture, medical applications, etc.