Nodes
A node is a resource that is available during execution time. (Nodes were mentioned in Chapter 2.) Traditionally, nodes refer to computers on a network, but in the UML a node may be a computer, printer, server, Internet, or any other kind of resource available to components. For example, the project management system may be deployed on the following nodes:
- A desktop client
On which the user interface component executes
- A printer
Which the project management system uses to print reports
- A business-processing server
On which the business-processing component executes
- A database server
On which the data component executes and where project-related information is stored
Nodes follow the type-instance dichotomy first discussed in Chapter 2 and applied to classes and objects in Chapter 3. You can use the UML to talk about classes of nodes, as well as specific nodes of a class. When speaking of a class of nodes, it’s customary to use the terms node or node class. Thus, while you might think of a node as a specific thing, in the UML, a node really represents a class of nodes. When speaking of a specific component of a class, use the term node instance.
A node is available during execution time and is a resource on which components may execute. In the UML, a node is shown as a three-dimensional rectangle labeled with the node’s name.
Figure 5-3 shows various nodes associated with the project management system, including a desktop client, business-processing server, database server, and ...
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