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warrencxw / pe

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Incorrect usage of the end of lifeline in sequence diagram #19

Open warrencxw opened 2 years ago

warrencxw commented 2 years ago

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Under Timetable usage scenario, in the second sequence diagram, a return arrow from Timetable class is drawn back to ShowCommand object, and a cross is marked on the ShowCommand object. This implies that the reference to the ShowCommand object is deleted or removed as soon as Timetable class returned control back to the ShowCommand object which is incorrect syntax here. What entity takes control after the the lifeline of ShowCommand object ends?

nus-se-script commented 2 years ago

Team's Response

As explained in the DG, this is one of the three part sequence diagram showing the steps taken when the user attempts to view his/her timetable for a specified day. ShowCommand is intended to be deleted as it will no longer be used. In the DG, it was explained that Main will execute a method within Showcommand. In this case, Showcommand will return back to main, and subsequently gets deleted after being used.

Items for the Tester to Verify

:question: Issue response

Team chose [response.Rejected]

Reason for disagreement: It is correct that ShowCommand is deleted as it will no longer be used. However, because in this case, the end of the lifeline indicated by the cross is exactly at the end of the activation bar, and there is no return arrow out of ShowCommand back to main, it appears that control is not returned to any other part of the application before ShowCommand is deleted. As such, either the application terminates there and then, which I assume that is not the case, or the diagram is incorrect. Of course, I will also be assuming that this is not intended to be a minimal sequence diagram as all other return arrows are drawn as well.