1. Capturing and Exploring Requirements with Use Cases and UML Models
Eddie Burris
UMKC

2. Writing Use Cases–Motivation
Writing use cases supports requirements activities:
Method of recording functional requirements.
Readable by end users but also detailed enough for programmers to implement and testers to write test cases.
Systematic and semi-formal representation helps ensure requirements are complete and well understood.

3. Visual Modeling–Motivation
Models are visual. They are potentially a more efficient and effective form of communication than prose.
Models are more precise. Hard to recognize missing elements in written forms of requirements. With a model, missing elements are more noticeable.
Models can represent ideas from different perspectives.
When to model? During requirements, design, and post-implementation.

4. Use Case—Definition
A use case is a narrative description of a goal-oriented interaction between the system under development and an external agent
Includes (the what):
User (Actor in Use Case Parlance)
Goal
Interaction
Excludes (the how):
User Interface Detail
Implementation Concerns

5. Use Case Template Title: Actors: Preconditions: Postconditions:
Basic Flow / Main Success Scenario
Alternate Flow / Extensions
Open Issues

6. Example Title: Search Web with suggested key words (Google Suggest)
Actors:
Web User
Preconditions:
Web user is at the search page
Basic Flow
User begins to enter search phrase
As characters of search phrase are typed, the system responds with suggested search phrases that start with characters entered
The system enters the highest ranking suggested search phrase into the search box where the user is typing
User scrolls to desired suggested phrase
User initiates search
System responds with search results that match search phrase
Alternate Flows
2a. There are no high ranking suggested search phrases for the characters the user has entered
1. The system gives no suggested search phrases
2. The user enters the remaining characters in the search phrase and control returns to step 5 in basic flow
4a. User decides to accept suggested search phrase in search box
1. User initiates search with suggested search phrase currently in search box
4b. User finishes entering original search phrase but doesn’t want to take system’s suggestion
1. User hits backspace to erase remaining suggested characters in search box
Open Issues
1. How to decide the order or ranking of suggested search phrases.

7. System Under Development
UML Use Case Diagrams
Newspaper Web Site
Post article
Journalist
Reader
Authenticate user
Find and read article
<<include>>
System Under Development
Use Case
Actor
Generic Form
Example

8. UML Diagram Types Static Dynamic Class Diagrams State Machine Diagrams
Activity Diagrams
Sequence Diagrams

9. UML Class Diagrams Generic Form Example Class Name Attributes
Relationship
Class Name
Attributes
Operations
Generic Form
CourseOffering
Student
10..30 *
is enrolled in
semester
Course
courseTitle 1
Example

10. UML State Machine Diagram
event [guard] action
Initial State
Final State
Empty
Ready for Business
stock
Ready to Dispense
[credit > purchase price]
[out of stock]
enter money / update credit
select beverage / reduce credit && dispense beverage && reduce stock
Generic Form
Example

11. Another State Machine Example
Waiting for Connection
do/play soothing music
Disconnected
do/Attempt connection
Connected
Connection
Established
after (1 min)
Introducing Application
entry/audio intro
after (2 min) / reassure user
[! disconnected] / announce connection
Waiting for Announceable building
do/look for next valid building
Lost
Connection Established
Newly Disconnected
[disconnected] / announce disconnection
Announcing Building
entry/ announce building
announceable building
Building announcement order
closest building that hasn’t already been announced.
After all buildings within a certain range have been announced you can reannounce a building if it has been 12 minutes since it was last announced or it has gone out of range and back into range since it was last announced.
This was used to explore an existing use case.

12. UML Activity Diagram Generic Form ... ... [cond] [cond] Activity
Transition
Branch
Merge
Generic Form

13. UML Activity Diagram Example
[User doesn’t have authority to access web page]
User Requests Web Page
Show Web Page
[else]
[Web page requires authorization]
Prompt for ID and password
User enters ID and password
[Invalid ID and/or password]
[Valid ID and password]
Issue
“not authorized” Message
[User has authority to access web page]
[Session established]
A junction point can be used to merge or split transitions.
[Web page doesn’t require authorization]
Predefined condition [else] evaluates to true if none of the other branch conditions evaluate to true.
Branch conditions may be placed on a state as an alternative to adding a branch diamond.
Example

14. The End