Sommerville-Software-Engineering-10ed

7.1 ■ Object-oriented design using the UML 201
System
Use case
Actors
Data
Stimulus
Response
Comments
Weather station
Report weather
Weather information system, Weather station
The weather station sends a summary of the weather data that has been collected from the
instruments in the collection period to the weather information system. The data sent are the
maximum, minimum, and average ground and air temperatures; the maximum, minimum,
and average air pressures; the maximum, minimum and average wind speeds; the total
rainfall; and the wind direction as sampled at 5-minute intervals.
The weather information system establishes a satellite communication link with the weather
station and requests transmission of the data.
The summarized data is sent to the weather information system.
Weather stations are usually asked to report once per hour, but this frequency may differ
from one station to another and may be modified in future.
Figure 7.3 Use case
description—Report
weather
how they respond to internal or external stimuli. Therefore, the stimuli and associated
responses should be listed in the description. Figure 7.3 shows the description of
the Report weather use case from Figure 7.2 that is based on this approach.
7.1.2 Architectural design
Once the interactions between the software system and the system’s environment
have been defined, you use this information as a basis for designing the system architecture.
Of course, you need to combine this knowledge with your general knowledge
of the principles of architectural design and with more detailed domain
knowledge. You identify the major components that make up the system and their
interactions. You may then design the system organization using an architectural
pattern such as a layered or client–server model.
The high-level architectural design for the weather station software is shown in
Figure 7.4. The weather station is composed of independent subsystems that communicate
«subsystem»
Fault manager
«subsystem»
Configuration manager
«subsystem»
Power manager
Communication link
Figure 7.4 High-level
architecture of
weather station
«subsystem»
Communications
«subsystem»
Data collection
«subsystem»
Instruments