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Sequence Diagram - Data Collection Subsystem

publish date: 1969/12/31 00:00:00 UTC

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In a sequence diagram showing the interaction between the data collection subsystem and instruments (e.g., Anemometer, Barometer) in the weather station, what sequence of messages correctly describes how the WeatherStation collects data from instruments?

The Satellite initiates data collection by sending a collect signal directly to each instrument

Instruments push data automatically to WeatherData without any request from WeatherStation

WeatherStation sends a collect() message to each instrument; each instrument collects sensor readings and stores them locally; when WeatherStation later calls getData(), each instrument returns its stored readings

WeatherData directly queries each instrument sensor without any intermediate object

Correct Answer

Explanation

In the data collection sequence: the WeatherStation (driven by a clock signal transitioning to Collecting state) sends a collect() message to each instrument object; each instrument object (Ground thermometer, Anemometer, Barometer) collects data from its associated sensor and stores it locally; WeatherStation then calls getData() on each instrument to retrieve the collected readings. The instruments operate autonomously - they collect data at the specified frequency and deliver it to WeatherData on request.

Reference

Software Engineering, Ian Sommerville, 10th edition

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