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An overview of use case modeling, including the concepts of actors, use cases, use case diagrams, and use case scenarios. Actors represent anything outside the system that interacts with it, and use cases document the behavior of a system from the user's point of view. Learn how to identify actors, create use case descriptions, and understand the advantages of use case diagrams.
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n Use Cases
n Actors
n Use Case Diagrams (Models)
n Use Case Scenarios n Analogy between Class Diagram and Use Case Diagram
n Identifying Actors n Use Case Descriptions
n Association and Relationships
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n document the behavior of a system from the user’s (actor) point of view n represent what the system must provide, rather than how n return/ provide some value to the user (actor)
UML Notation
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n An actor represents anything outside the system that will interact with the system n Can be a human n Can be a software n Can be a hardware n Each actor uses the system in a different way, otherwise they should be the same actor n Each way actor uses the system is a Use Case
UML Notation
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n Primary Actors n Payroll Clerk n Registrar of a University n BookBorrower n Secondary Actors called by the system to complete a use case n Printer n Some application
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n Active n Initiate activity with the system n Computer users with computer n Phone users with phone n Payroll Clerk with Payroll system n Internet subscriber with web browser n Get some value in return
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n Identification of actors interacting with different systems
n Recognizing functionalities of different (sub-) systems become easier
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n Show primary actors on left side of diagram
n Show secondary actors on right side of diagram
n UC must provide a real service to the user
n Keep drawings neat and clear n Do not put too many UCs in one diagram
n Number UCs for easy reference
n Maintain a catalog of use case number to use case name to avoid duplicates
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n A session that an actor has with the system n A detail of real data and actual expected output
n A use case contains all the events that can occur between an actor-use case pair, not necessarily the ones that will occur in any particular scenario n A use case contains a set of scenarios that explain various sequences of interaction within the transaction (session)
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n The two diagrams are similar n They represent n A set of things n possible interactions n Class Diagram: n A set of objects n A particular Student may or may not be taking a particular Module n UC Diagram: n A set of role-players and a set of scenarios n A particular BookBorrower may or may not be involved in a book reservation scenario
Student Module
BookBorrower Borrows a copyof book
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n Actor in a use case diagram represents a role rather than a particular individual n The communication relationship does not signify that someone in a role will necessarily be involved in a particular scenario
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n Users of the system n Other systems interacting with this system
n Finding human actors n Finding non-human actors
