This document contains instructions for three state diagram modeling exercises: 1. A vending machine where a user inserts coins that are identified, can enter multiple coins, retrieve coins without purchasing, select products, and receive products or remaining money depending on available funds. 2. An online library where a user authenticates, searches for books by parameters, views results, can download free books or is directed to a purchase page for non-free books before downloading. 3. A user should model each system with a state diagram, explaining the events, conditions, and actions for transitions.

1. Helwan University
Faculty of Engineering
Department of Electronics, Communications & Computer
ELC 9321 Software Engineering - Spring 2017
Sheet Five – UML State Diagram
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1- Explain events, conditions, actions for transitions for this diagram
2- In a vending machine system, the user enters a coin in a machine the machine
identifies the inserted coin to be a half a pound or a pound else the inserted coin is
dropped down back to the user. The user can enter amount of money as much as he
wants. Also he can get back the amount he wanted without ordering anything. He can
order any product by inserting the corresponding button. If the product doesn’t exist
he will be notified to change the product. If the amount he entered is sufficient or
higher the product is dropped to him and the remaining money. If not he will be
notified to enter more money or he can drop it. If the user freezes without any action
for 3 minutes the money he entered will be dropped. Make a state Diagram that
Explain events, conditions, actions for this diagram.
3- In an Online library Management system, The User Authenticate his identity either by
login or registration. A user then can searches any book based on the parameters he
enters i.e. Name of the book, Author, Type, etc. then he is shown the list of books that
suits is search query. If he likes any of the shown books he can click download on any

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of the shown book. Books are marked Free, Non Free, if the book is free he can
download it directly if not the user is then directed to page that he must confirms that
the website will take this amount of money (depending on the book price), if yes he
can download the book. Else he will return to the search page. Make a state Diagram
that Explain events, conditions, actions for this diagram.
Best Wishes,
Dr. Amr E. Mohamed