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

Getting Started

If you are building a house, things like walls, doors, windows, cabinets, and lights will form part of your vocabulary. None of these things stands alone, however. Walls connect to other walls. Doors and windows are placed in walls to form openings for people and for light. Cabinets and lights are physically attached to walls and ceilings. You group walls, doors, windows, cabinets, and lights together to form higher-level things, such as rooms.Associations are structural relationships among instances. For example, rooms consist of walls and other things; walls themselves may have embedded doors and windows; pipes may pass through walls.

These three kinds of relationships cover most of the important ways in which things collaborate with one another. Not surprisingly, they also map well to the ways that are provided by most object-oriented programming languages to connect objects.

The UML provides a graphical representation for each of these kinds of relationships, as Figure 5-1 shows. This notation permits you to visualize relationships apart from any specific programming language, and in a way that lets you emphasize the most important parts of a relationship: its name, the things it connects, and its properties.