Class and Object Diagrams (
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This article will teach you about UML structural diagrams, used to help you keep track of the structure of your models. It was excerpted from chapter three of Fast Track UML 2.0, written by Kendall Scott (Apress, 2004; ISBN: 1590593200).
THIS CHAPTER FOCUSES ON THE UML STRUCTURAL diagrams that you use to capture the fundamental structure of your models at the class and object levels.
Class Diagrams
A class diagram focuses on a set of classes (see Chapter 1) and the structural relationships among them (see Chapter 2). It may also show interfaces (see the section “Interfaces, Ports, and Connectors” in Chapter 1).
The UML allows you to draw class diagrams that have varying levels of detail. One useful way to classify these diagrams involves three stages of a typical software development project: requirements, analysis, and design. These stages are discussed in the following sections.
Domain-Level Class Diagrams
A domain-level class diagram shows just the names of classes. The purpose of the diagram is to show part of the initial core vocabulary with which system modeling can proceed.
NOTE Domain-level class diagrams are directly comparable to platform-independent models (PIMs) within Model-Driven Architecture (MDA). See MDA Distilled1 for more information about MDA.
Figure 3-1 shows an example of a domain-level class diagram.
Figure 3-1. Domain-level class diagram
The layout of this diagram suggests five conceptual groupings of classes around which more expansive diagrams might center. Starting in the upper-left corner and moving clockwise, these groupings are as follows:
- PurchaseOrder, Shipment, and Stock
- Category, Catalog, Book, BookAndAuthor, and Author
- Customer, Account, BillingInfo, and ShippingInfo
- Item, ShoppingCart, Order, and OrderHistory
- GLAccount
In the meantime, this diagram provides a view of a useful cross section of the relevant starting classes.
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