Use Case
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This document defines use cases, use case diagrams, and their elements and purposes. It explains that use cases describe interactions between actors and a system to achieve a goal. Key elements are actors, the system boundary, use cases, and relationships between use cases like include, extend, and generalization. Use case diagrams help validate system architecture, specify context, define requirements, and guide implementation. They benefit projects by outlining user goals and system needs but can be difficult by requiring prototypes, limiting non-functional requirements, taking time, and having limited tool support.
Use Case
- 1. UseCase
- 2. Definition of use case CONTENTS Use Case Symbols Difficulties With Use Case Diagram Use Case Elements Use Case - Relationships Example Of Use Case Relationship Building Use Cases Use Case diagram- Example Purpose of Use Case Diagram Benefits Of Use Case Diagram
- 3. Definition Of Use Case
- 4. Use Case Actor Boundary Connection Include relationship Extend relationship <<include>> <<extend>> Use Case Symbols
- 5. 01 Actor 02 Use Case 03 Communication USE CASE ELEMENTS
- 6. 03 02 01 Actor Use Case Element s The actor(s) who trigger the use case to activate. An Actor is outside or external the system. It can be a: • Human • Peripheral device (hardware) • External system or subsystem • Time or time-based eventIt is represented by stick figure. Actor
- 7. 03 02 01 Use Case Use Case Element s A use case in a use case diagram is a visual representation of a distinct business functionality in a system. A use case is a summary of scenarios for a single task or goal. For example- The figure shows in below have two use cases: "Make appointment" and "Perform medical tests" in the use case diagram of a clinic system. Use case Fig: Use cases in a use case diagram
- 9. Depicted by line or double-headed arrow line Represent communication between actor and use case Use Case - Relationships Association Relationship:
- 10. USE CASE - RELATIONSHIPS Make Appointment System Boundary:
- 12. Child use case Parent use case Generalization Relationship: A generalization relationship is also a parent-child relationship between use cases. In a use case diagram, generalization is shown as a directed arrow with a triangle arrowhead. The child use case is connected at the base of the arrow.
- 13. 03 Write << include >> above arrowhead line 02 Arrow is drawn from the base use case to the used use case 01 Represents the inclusion of the functionalit y of one use case within another Include Relationship
- 14. 03 Write << extend >> above arrowhead line 02 Arrow is drawn from the extensi on use case to the base use case 01 Represents the extension of the use case to include optional functionalit y Extend Relationship
- 16. 01 Identify the major use cases Activities: Start a use case form for each use case If more than nine, group into packages Step 02 Identify the major steps within each use case Activities: For each use case, fill in the major steps needed to process the inputs and produce the outputs Step 03 Identify elements within steps Activities: For each step, identify its triggers and its inputs and outputs Step 04 Confirm the use case Activities: For each use case, validate that it is correct and complete Step BUILDINGUSECASES
- 18. Developed by analysts together with domain experts Validate a systems architecture Specify the context of a system Defining and organizing functional requirements in a system Drive implementation and generate test cases Capture the requirements of a system PURPOSE OF USE CASE DIAGRAM Use case diagrams are typically develop in early stage of development and people often apply use case modeling for the following purposes:
- 19. 01 Detailing user interaction goals with a product 02 Use cases are determining the specific needs of a project 03 Use cases provide a contractual delivery process 04 Use cases provide an easily understood communication mechanism 05 Outlining and ensuring the requirements of a system 06 Modeling the basic flow of events in a use case BENEFITS OF USE CASES
- 20. Require the co-existence of prototypesNumber 04 They do not capture the non- functional requirements easily Number 03 Time-consuming to generateNumber 02 Limited software tool supportNumber 01 DIFFICULTIES WITH USE CASES
Editor's Notes
- #11: System boundary: A system boundary defines the scope of what a system will be. A system cannot have infinite functionality. So, it follows that use cases also need to have definitive limits defined. A system boundary of a use case diagram defines the limits of the system. The system boundary is shown as a rectangle spanning all the use cases in the system. Other use cases in this lecture also show the system boundary of the clinic application. The use cases of this system are enclosed in a rectangle. Note that the actors in the system are outside the system boundary. The system boundary is potentially the entire system as defined in the problem statement. But this is not always the case. For large and complex systems, each of the modules may be the system boundary. For example, for an ERP system for an organization, each of the modules such as personnel, payroll, accounting, and so forth, can form the system boundary for use cases specific to each of these business functions. The entire system can span all of these modules depicting the overall system boundary.
- #13: Inheritance A use case generalization shows that one use case is simply a special kind of another. A clinic may have a use case such as Pay Bill which would be a parent use case and Bill Insurance which is the child. A child can be substituted for its parent whenever necessary. Generalization appears as a line with a triangular arrow head toward the parent use case.