1. Object-Oriented Sequence Diagrams
CMIS 570
Anne Powell, Ph.D.
Object-Oriented Sequence Diagrams
Week 10
CMIS 570
SIUE

2. Sequence Diagrams
Illustrates the objects that participate in a use-case and the messages that pass between them over time for one use-case.
A dynamic model
Most similar to a DFD Level 0

3. Patient Admission example
A patient will call in to schedule an appointment or cancel an appointment. The office employee should be able to look up the patient’s name to determine if this is an existing patient. The office employee should also be able to lookup any existing unpaid bills the patient may have with the doctor’s office. The system will look up available times and dates for an appointment. When a day/time works for the patient, the system will add a new appointment.
Before available days and times can be recorded, an employee of the doctor’s office will need to create a master schedule. This master schedule will list all the doctor’s schedules and the days and times the office will be open for appointments.
A doctor can alter his or her schedule. When this occurs, the doctor will inform the employee of any days/times when he/she is not available. In addition, the doctor can add days/times when he/she is available to see patients.

4. Elements of a Sequence Diagram
Text
Objects
Message or interaction
Message Condition
Dotted Line
Focus of Control or Activation

5. Object creates Object
If object creates an object, message is sent directly to an object instead of its activation line.

6. Creating a Sequence Diagram
1. Copy text for use case from the use case specifications (documentation). Paste it onto the left margin of the page.
2. Identify Objects
3. Add messages
4. Place lifeline and focus of control

7. More Examples
Rent a Car
E-commerce purchase

8. Rent a Car
The Cougar Car Rental Agency rents cars to customer at the airport. Customers can call in to reserve a vehicle, but ultimately they must go to the Rental desk at the airport to rent the car (with or without a reservation).
The car rental agents work behind the counter, taking phone reservations and waiting on “walk-up” customers who wish to rent. When renting a car to a customer, the rental agent fills out the customer and rental car information on a rental contract, has the customer provide a credit card number as a down payment, has the customer sign the rental contract, and provide the customer a copy of the rental contract along with the keys for the rental car.
Cougar Agency also has service technicians who clean the cars when customers return them, fill cars with gas, and prepare the cars for the next rental. The service technicians also make sure that the cars receive their regular maintenance, such as oil changes, and schedule other service when the cars are in need of repair. Also, Cougar has only a limited number of each type of vehicle to rent.

9. E-commerce purchase
Using the web, customers should be able to search for products and identify if the item is available. They should be able to order the item. The documentation from the use case is below:
Look up marketing material on product.
Search inventory to see if product is available.
Place item in shopping cart.
Create order by providing shipping and billing information.
Customer provides final acceptance of order.

10. Enrolling in a Fitness Class
When a student wants to add a new class, the manager will check the fitness class schedule for availability. The manager will notify the student of an opening, and the student will pay the fee if there is an opening. The student is then registered for the class.
As new instructors are hired, their availability to teach a class will be recorded. Information on the type of class the instructor is certified to teach as well as the times he/she is available is recorded.
At times, the fitness class schedule must be changed. When this occurs, the manager will change the fitness schedule, and will then notify the instructors and students who are affected by the change.

11. TIPS Don’t turn your sequence diagram into a flowchart
Update existing models

12. Modification of Class Diagram
Similar to DFDs and ERDs, after creating a Sequence Diagram, you may alter your Class Diagram.

13. For Next Class Meeting…
DDT
Table API