11.3. Definition: What is a System Operation?
Operation contracts may be defined for system operations operations that the system as a black box component offers in its public interface. System operations can be identified while sketching SSDs, as in Figure 11.2. To be more precise, the SSDs show system events events or I/O messages relative to the system. Input system events imply the system has system operations to handle the events, just as an OO message (a kind of event or signal) is handled by an OO method (a kind of operation).
Figure 11.2. SSD. System operations handle input system events.
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