Section B.6. Working with the Meta-Model

B.6. Working with the Meta-Model

At this point, you may be thinking that the model in Figure B-6 looks similar to the other UML models you've seen in this book. However, it contains some striking differences: the WebService stereotype is related to the element Class for one, and the extension arrow is different from the previous relationships you've seen for another. Normally, you would never explicitly refer to Class in your UML models because it is a UML meta-model element.

The term meta-model was introduced in Chapter 1.Meta-models define rules about how the UML elements work, e.g., a class can have a subclass or a class can be associated with any number of other classes. When you are modeling a profile you are working with the meta-model, customizing the regular UML's rules for a particular context.

This customization of UML for your particular context may sound dangerous at first, almost like you are making up your own language! This is actually not the case, profiles are a safe and controlled way of customizing UML, but should be used only when you really need them (see "Why Bother with Profiles?"). They can be a powerful way of making your model mean much more than it would do with standard UML alone.