In UML, a "classifier" is an element that represents an entire category of things within the system. Classes, interfaces, and actors are examples of classifiers. Classifiers can contain attributes (colloquially called "fields") that describe instances of the classifier and operations (colloquially called "methods") that describe what an instance of the classifier can do. In the case of classes, these can be edited via diagrams.
All classifiers (including classes) can be edited via their Detail Pages. Besides the usual Detail Page controls, the Detail Page for a classifier contains an Attributes button and an Operations button:
When you click the Attributes button, the Attribute List dialog will appear.
When you click the Operations button, the Operation List dialog will appear.
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Copyright © 2006 by Martin L. Shoemaker/The Tablet UML Company.