1. Use Case Modeling

2. Commonly Used UML Diagrams
The most commonly used UML diagrams are:
Use case diagram, describing how the system is used.
The starting point for UML modeling.
Use case (not a diagram).
Activity diagram.
Each use case may create one activity diagram.
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3. Commonly Used UML Diagrams
The most commonly used UML diagrams (continued):
Sequence diagram, showing the sequence of activities and class relationships.
Each use case may create one or more sequence diagrams.
A collaboration diagram is an alternative to a sequence diagram.
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4. Commonly Used UML Diagrams
The most commonly used UML diagrams (continued):
Class diagram, showing classes and relationships.
Sequence diagrams and CRC cards are used to determine classes.
Statechart diagram.
Each class may create a statechart diagram, useful for determining class methods.
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5. Overview of UML Diagrams
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6. Use Cases
Depiction of a system’s behavior or functionality under various conditions as the system responds to requests from users
Full functioning for a specific business purpose

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Use Case Diagram
A use (yoos) case describes what the system does, not how it does the work.
The use case model reflects the view of the system of the user outside of the system.
Symbols are:
Actor, a stick figure.
Use case, an oval.
Connecting lines.
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8. UML Use Case Diagram Symbols
Use Case Actor Boundary Connection Include relationship Extend relationship
<<include>>
<<extend>>

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Actors
Represent role played by one or more users
Exist outside of the system
May be a person, another system, a device, such as a keyboard or Web connection
Can initiate an instance of a use case
May interact with one or more use cases and a use case may involve one or more actors
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Actors (Continued)
Actors may be divided into two groups:
Primary actors supply data or receive information from the system
Secondary actors help to keep the system running or provide help
Help desk, analysts, programmers, etc.
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11. What is a Boundary?
A boundary is the dividing line between the system and its environment.
Use cases are within the boundary.
Actors are outside of the boundary.

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Use Case
Consists of three things:
An actor (user) that initiates an event.
An event that triggers a use case.
The use case that performs the actions triggered by the event.
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Use Case (Continued)
Better to create fewer use cases
20 use cases for a large system
50 use cases would be the maximum for a large system
Can nest use cases, if needed
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14. What is a Connection?
A connection is an association between an actor and a use case.
Depicts a usage relationship
Connection does not indicate data flow

15. Use Case Relationships
Communicates
Connect an actor to a use case
Includes
Use case contains a behavior that is common to more than one use case.
The common use case is included in other use cases.
Dotted arrow points toward common use case.
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16. What is an <<include>> Relationship?
A connection between two use cases
Indicates a use case that is used (invoked) by another use case
Links to general purpose functions, used by many other use cases

17. Use Case Relationships (Continued)
Extends
A different use case handles variations or exceptions from the basic use case.
Arrow goes from extended to basic use case.
Generalizes
One thing is more general than another thing.
Arrow points to the general thing.
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18. What is an <<extend>> Relationship?
A connection between two use cases
Extends a use case by adding new behavior or actions
Specialized use case extends the general use case

19. Use Case Relationships
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22. Steps for Creating a Use Case Model
The steps required to create a use case model are:
Review the business specifications and identify the actors within the problem domain.
Identify the high-level events and develop the primary use cases that describe the events and how actors initiate them.
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23. Steps for Creating a Use Case Model
The steps required to create a use case model are (continued):
Review each primary use case to determine possible variations of flow through the use case.
Develop the use case documents for all primary use cases and all important use case scenarios.
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