Understanding the UML model hierarchy |
This tutorial introduces the concept of the UML model hierarchy and discusses the components of a UML model such as model elements, diagram elements, and diagrams. A UML model is a collection of UML elements, diagrams, and data such as relationships and requirements information, that describe a real-world system. A software architect uses UML to build models that describe the quantifiable characteristics of a system such as the system's structure, behavior, contraints, and dependencies. The building blocks of a UML model are called model elements. Model elements are the data representation of a real world object, actor, or system. A UML diagram provides a visual representation of a specific aspect or behavior of a system. A UML diagram describes the quantifiable aspects of a system that can be visually described, such as relationships, behavior, structure, and functionality. For example, a use case diagram describes the interactions between the users of the system, called the actors, and the system. A class diagram is often used to describe the structure of a system, or the details of an implementation. A UML diagram contains diagram elements (sometimes called shapes) that visually describe the classifiers in a diagram. These classifiers are the diagrammatic representation of a model element. UML diagrams provide views of UML models, however, diagram elements are not considered part of the semantic model. A UML model might or might not contain a UML diagram. Many UML models contain more than one diagram. A UML model can also contain one or more sub models. IBM Rational® Software Architect® provides a flexible development environment for creating and editing UML models. You can use the Model Explorer view to edit the source code and model structure of the semantic model, and you can use the diagram editor to edit the visualized model. When you edit models, you should understand the differences between model elements and diagram elements. For example, when you right-click an element in the diagram editor, there are two delete options. If you click Delete from Diagram, the element is deleted from the diagram only, because the diagram element is only a visualization of a model element. Conversely, if you click Delete from Model, the element is deleted from both the model and the diagram. By default, when the user selects a diagram element and presses the Delete key or when the user selects a diagram element and clicks File > Delete, the element is removed from the diagram only. This tutorial is intended for users with little or no experience with the product.
Learning objectivesThis tutorial describes the differences between a UML model and a UML diagram. The tutorial shows you how to do the following things:
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