A system use cases are the first major model created

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Unformatted text preview: al modeling tools 15 16 Use Cases • Use cases are logical models that describe the functions and activities of a system – Use cases are the first major model created in the objectoriented software development – Use cases are often used in subsequent stages of the object-oriented software development process to validate design, develop test cases, develop user manuals Use Case Model • A use case model describes the uses of the system and shows the major functions and courses of events that can be performed – Use cases are scenarios for understanding system requirements • A use case model is a complete set of diagrams and use case descriptions to represent how actors interact with a system – Diagrams • Context Diagram: shows actors and system boundaries • Use Case Diagram: shows actors and all use cases • Use cases describe a system from the actors’ perspective – A collection of scenarios that describe actors using a system to support a goal – A behavior of the system that produces a result of value to the actor 17 – Use case descriptions: 3 levels of use case descriptions • Initial use case descriptions • Base use case descriptions • Elaborated use case descriptions 18 Sample Context Diagram Sample Use Case Diagram 19 20 Levels of Use Cases Initial Use Case Include Include only general use case descriptions Sample Initial Use Case Description Use Case ID Use Case Actors Description UC-100 Withdraw Funds (P) Customer The customer inserts card in the ATM, logs in with a pass code, and makes a selection from the available choices to withdraw funds. Once in the funds withdrawal screen, the customer is prompted to enter the amount to withdraw. After the amount is entered, the system will check for availability of funds for that customer. Provided that funds are available, the system will dispense the amount requested in cash and then debit that amount in the customer’s bank account records. High Cash dispensed within 10 seconds after amount is entered Customer speaks English Bank’s Operational Procedures Manual 22 Base Use Case Provide a complete description of the normal set of primary interactions (flows of events) Elaborated Use Case Add alternative and conditional flows of events, if any Develop extended and included use cases, if appropriate Priority Non-Functional Requirements Assumptions Source 21 Sample Base Use Case Description Use Case ID Use Case Actors Description Pre-conditions Flow of Eve...
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This note was uploaded on 12/22/2010 for the course ISOM ISOM221 taught by Professor Sheunhhee during the Spring '09 term at HKUST.

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