SSD09 Exam02 Practical

详情见附件

1. Use the technique of noun extraction to identify the possible classes in the following use case scenario for a software system that controls an assembly line:

   The sensor sends a STOP message to the control software if a widget reaches the end of the conveyor belt without being lifted by the robot arm. The software sends a signal to the motor controller to stop the assembly line.

   Which of the candidate classes should not be added to the preliminary class list? Refer explicitly to the refinement principle you used in each case.

   
   
2. Draw an object diagram for the classes you identified in Question 1. Be sure to include any class attributes or methods that resulted from preliminary class refinement.
   
   
3. Does the object diagram you drew for Question 2 use the principle of responsibility-driven design in the assignment of messages (method calls) to classes? Justify your answer.
   
   
4. Draw a UML state transition diagram to model the control program for a portable CD player. Include three states: stopped , playing , and paused . Also, include three events possible in any state: pause_is_pressed , stop_is_pressed , and play_is_pressed .
   
   
5. Draw a UML sequence diagram that models the following events in a three-tier database client-server architecture:

   The client applet sends a connection request to the database servlet, which sends back a password request. The user supplies a username and password, which are sent back to the database servlet. The username and password are correct, so the servlet responds with an "OK" message. The user enters search parameters in the applet interface, and the client applet translates these into an SQL query, which is sent to the database servlet. The database servlet sends the SQL query to the remote database, which sends back the results of the query. The servlet passes the results back to the client applet.