The Unified Modeling Language User Guide SECOND EDITION [Electronic resources] نسخه متنی

Common Modeling Techniques

Modeling Concrete Instances

When you model concrete instances, you are in effect visualizing things that live in the real world. You can't exactly see an instance of a Customer class, for example, unless that customer is standing beside you; in a debugger, you might be able to see a representation of that object, however.

One of the things for which you'll use objects is to model concrete instances that exist in the real world. For example, if you want to model the topology of your organization's network, you'll use deployment diagrams containing instances of nodes. Similarly, if you want to model the components that live on the physical nodes in this network, you'll use component diagrams containing instances of the components. Finally, suppose you have a debugger connected to your running system; it can present the structural relationships among instances by rendering an object diagram.

To model concrete instances,

• Identify those instances necessary and sufficient to visualize, specify, construct, or document the problem you are modeling.

• Render these objects in the UML as instances. Where possible, give each object a name. If there is no meaningful name for the object, render it as an anonymous object.

• Expose the stereotype, tagged values, and attributes (with their values) of each instance necessary and sufficient to model your problem.

• Render these instances and their relationships in an object diagram or other diagram appropriate to the kind of the instance.

For example, Figure 13-6 shows an object diagram drawn from the execution of a credit card validation system, perhaps as seen by a debugger that's probing the running system.