07 uml use case diagrams
TRANSCRIPT
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UML Use Case Diagrams How use cases relate to one another
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A use case diagram shows all use cases and their relationships with one another and all actors
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Use case diagram = use cases + actors + relationships ¡ Actor = an external entity that might interact with
our system ¡ To create a use case diagram, we
1. define the system 2. find the actors 3. find the use cases 4. define the relationships between them
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An example of a use-case diagram
Insurance Salesperson
Customer
Sign an insurance policy
Sales statistics
Customer statistics
Actor Use case
System box
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An actor is an external thing interacting with the system
Insurance Claims System
Claimant
Claims Rep
Billing System
Agent
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Manage Claim
Claimant
Claims Rep
Payment System
Agent Review Claim
Status
Use cases are activities that the system does for the actors
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Example: Simple Order Entry System
Customer
Browse Products & Place Orders
Allows a customer to browse through a product catalog and
place orders for items
A person who may acquire products
Credit Institution
An organization that provides credit on
demand to customers
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Use brainstorming to find your initial set of actors ¡ You'll find most of your actors in a brainstorming
session ¡ Then start your use case development ¡ Other actors will reveal themselves as you realize
the use cases
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Brainstorming questions help to find actors ¡ Who starts and stops the system? ¡ Who does user and security management? ¡ Who does system administration? ¡ Is the system automated via cron? If so, time is an actor ¡ Is there a monitoring process that restarts the system if it fails? ¡ How are software updates handled? ¡ Who evaluates system activity or performance? ¡ Who will use the main functionality of the system? ¡ Who will need support from the system to do their daily tasks? ¡ Who will need to administrate and keep the system working? ¡ Which hardware devices does the system need to handle? ¡ With which other systems does the system need to interact? ¡ Who or what cares about the results that the system produces?
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Primary actors start an activity
Secondary actors merely get value from the system
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Conclusion ¡ The use case diagram gives us a high-level view
of all of the use cases, the actors, and how they relate among themselves
¡ You'll find your initial set of use cases based on the functional requirements
¡ You'll find your initial set of actors by brainstorming
¡ As you analyze further, more use cases and actors will reveal themselves