In this component diagram example, there are three user interfaces:
- one each for customers using a Ticket Selling System
- clerks using the on-line reservation system
- supervisors making queries about ticket sales.
- There is a ticket seller component that sequentializes requests from both ticket selling system and clerks
- A component that processes credit card charges; and the database containing the ticket information.
The component diagram shows the kinds of components in the system; a particular conﬁguration of the application may have more than one copy of a component. A small circle with a name is an interface—a coherent set of services. A solid line from a component to an interface indicates that the component provides the services listed in the interface. A dashed arrow from a component to an interface indicates that the component requires the services provided by the interface.
For example, subscription sales and group sales are both provided by the ticket seller component; subscription sales are accessible from both ticket selling and clerks, but group sales are only accessible from a clerk.