The document discusses use case diagrams and their components. It defines key terms like actors, use cases, and relationships between use cases. It explains that use case diagrams model interactions between actors and a system, and capture the system's functional requirements. Diagrams show actors outside the system boundary and use cases inside it. Relationships like "include", "extend", and "generalization" define relationships between use cases. The document provides examples and guidelines for creating use case specifications that describe use case scenarios in detail.

1. 1
Use case DiagramUse case Diagram
Use case specificationUse case specificationUse case specificationUse case specification
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2. USE CASE DIAGRAMUSE CASE DIAGRAM
System behavior is captured by use cases.
– Use cases describe the system, its environment,
and the relationship between the system and
its environment.its environment.
– “A use case diagram is a graphic representation
of the key features of the written use case
reports that comprise a system.”
(McLeod, Jordan)

3. What Is a Use-Case Model?
• A model that describes a system’s functional
requirements in terms of use cases
• Represents
– system’s intended functionality (use cases)
and its environment (actors)

4. What Is an Actor?
Actors are not part of the system.
Actors represent
roles a user of the system can play.
 anything that interacts with the system
 a human, a machine, or system.
Actors are EXTERNAL.
 a human, a machine, or system.
They can actively interchange information
with the system.
They can be a giver of information.
They can be a passive recipient of
information. Actor

5.  Who will supply, use, or remove information?
 Who will use this functionality?
 Who is interested in a certain requirement?
 Where in the organization is the system
Useful Questions in Finding Actors?Useful Questions in Finding Actors?
Actor
 Where in the organization is the system
used?
 What are the system’s external resources?
 What other systems will need to interact with
this one?

6. USEUSE CASECASE:: a sequence of actions a
system performs that yields an
observable result of value to a
particular actor. Use Case
Use Cases and ActorsUse Cases and Actors
A use case models a dialog between actors and the
system. A use case is initiated by an actor to
invoke a certain functionality in the system.

7. QuestionsQuestions toto findfind useuse casescases..
– For each actor you have identified,
what are the tasks the system would
be involved in?
– Does the actor need to be informed
about certain occurrences in theabout certain occurrences in the
system?
– Will the actor need to inform the
system about sudden, external
changes?
– What information must be modified or
created in the system?

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9. Brief Overview of Use Case Core
Components and Structure

10. Brief Overview of Use Case Core
Components and Structure

11. Relationship between Use-CaseRelationship between Use-Case

12. – Use the include relationship to show
that
•the behavior of one use case is wholly and
unconditionally used in another use case
Perform Transaction
The Perform Transaction
use case includes the
Perform Transaction
Send Command Receive Response
Application «include» «include»
use case includes the
processing specified by
both the Send Command
and Receive Response
use cases.

13. Use Case Diagram Rules
• Use the generalizationgeneralization relationship to show
that
– a use case is a specialization of another
use case
Run Applications Install Applications
User Super User
A User can Run Applications.
A Super User can Install
Applications and Run
Applications, since a Super
User is a specialization of
User.

14. • Use the extendextend relationship to show that
– one use case conditionally augment (or
extend) the behavior of another use
case.

15. 1. Actor
2. Use case
3. Association
4. System Boundary
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16. 5. Include
6. Extend
7. Generalization
8. Dependency
9. Comment
10. Artifact
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17. Types of Actors
1. Initiating actor ( primary actor or “user”):
initiates the use case to realize a goal
2. Participating actor (Secondary actor):
participates in the use case but does not initiateparticipates in the use case but does not initiate
it:
3. Supporting actor:
helps the system-to-be to complete the use case
4. Offstage actor: passively participates in the
use case, i.e., neither initiates nor helps
complete the use case

18. Practice: Find the Actors
• In the Course Registration System Requirements
document, read the Problem Statement for the
Course Registration case study.
• As a group, identify the following
– Actors
– Description of the actor

19. Use-Case Specifications
• Name
• Brief description
• Flows of Events
• Relationships
• Activity diagrams
Use-Case Model
Actor• Activity diagrams
• Use-Case diagrams
• Special
requirements
• Pre-conditions
• Post-conditions
• Other diagrams Use-Case Specifications
...
Actor
s Use
Cases

20. Brief Overview of
Use Case Core Components and Structure –
Use Case Description
Basic Structure and
Components
• Use Case: Name
• Brief Description
Additional Components
• Special Requirements
• Data Sources *
• Brief Description
• Actors
• Pre-Conditions
• Post-Conditions
• Basic Flow
• Alternate Flows
• Exception Flows
• Data Sources *
• Dependencies
• Assumptions
• Open Issues

21. Scenarios..
•Scenario: a set of actions performed to
achieve a goal under some conditions
– Actions specified as a sequence of steps
– A step is a logically complete action performed– A step is a logically complete action performed
either by the actor or the system
•Main success scenario – when things go
normally and the goal is achieved
•Alternate scenarios: When things go wrong
and goals cannot be achieved
21

22. Example 1
Use Case 1: Buy stocks
Primary Actor: Purchaser
Goals of Stakeholders:
– Purchaser: wants to buy stocks
– Company: wants full transaction info
Precondition: User already has an account
Main Success Scenario
Requirements 22
Main Success Scenario
User selects to buy stocks
System gets name of web site from user for trading
Establishes connection
User browses and buys stocks
System intercepts responses from the site and updates
user portfolio
System shows user new portfolio standing

23. Alternatives
2a: System gives error message, asks for new
suggestion for site, gives option to cancel
3a: Web failure.
1. Sys reports failure to user & backs up to
previous step.
2. User exits or tries again
4a: Computer crashes4a: Computer crashes
4b: web site does not acknowledge purchase
5a: web site does not return needed info
Requirements 23

24. Example 2
• Use Case 2: Buy a product
• Primary actor: buyer/customer
• Goal: purchase some product
• Precondition: Customer is already logged in
Main Scenario
Customer browses and selects items
Customer goes to checkout
Requirements 24
Customer goes to checkout
Customer fills shipping options
System presents full pricing info
Customer fills credit card info
System authorizes purchase
System confirms sale
System sends confirming email

25. Alternatives
6a: Credit card authorization fails
Allows customer to reenter info
3a: Regular customer
System displays last 4 digits of credit card
no
Asks customer to OK it or change it
Moves to step 6
Requirements 25

26. Student Assignment
5 Marks
Submission Date:
14 – Nov – 201414 – Nov – 2014
Friday

27. Analyze the given Use Case Diagram
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28. Answer the following questions
1.Which use cases will a 1.5 Marks
 STUDENT be able to perform?
 PROFESSOR be able to perform?
 REGISTRAR be able to perform?
2.Identify 2 types of actors ? 0.5 Marks
3. Identify 2 types of relationships and write clearly3. Identify 2 types of relationships and write clearly
which relationship between which elements 0.5 Marks
4. Which use case needs to run first, Register for
Courses or View Report Card? 0.5 Marks
5. If Charlie is a student and professor, which use
cases will he be able to execute 1 Mark
6. Describe the functionality of this system. 1 Mark
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