University Of Palestine

1. University Of Palestine College of Applied Engineering & Urban PlanningSoftware Engineering Department

2. Requirements Engineering Requirements Engineering

3. Presents

4. Understanding User Requirements Understanding User Requirements 2st Term2009/2010

5. Introduction The Use-Case Approach Event-Response Tables References 1 2 3 4 Contents

6. 1. Introduction • People employ software systems to accomplish useful goals, and the software industry is exhibiting an encouraging trend toward designing software to enhance usability. • A necessary prerequisite to designing software for use is knowing what the users intend to do with it.

7. 1. Introduction • For many years, analysts have employed usage scenarios to elicit user requirements. • Scenarios are real-life examples of how a system can be used. • They should include • A description of the starting situation. • A description of the normal flow of events. • A description of what can go wrong. • Information about other concurrent activities. • A description of the state when the scenario finishes.

8. 1. Introduction • A requirements technique often used for real-time systems is to list the external events to which the system must react and the corresponding system responses. • Use-cases are a scenario based technique in the UML which identify the actors in an interaction and which describe the interaction itself. • A set of use cases should describe all possible interactions with the system. • Sequence diagrams may be used to add detail to use-cases by showing the sequence of event processing in the system. • This Presents describes the application of both use cases and event-response tables to capture user requirements.

9. The Use-Case Approach The Use-Case Approach The Use-Case Approach The Use-Case Approach Use-case diagrams Use Cases and Usage Scenarios use cases Identifying Use Cases Documenting Use Cases Use Cases & Functional Requirements 2. The Use-Case Approach

10. 2. The Use-Case Approach • 2.1 use cases • A use case describes a sequence of interactions between a system and an external actor. An actor is a person, another software system, or a hardware device that interacts with the system to achieve a useful goal . • Another name for actor is user role, because actors are roles that the members of one or more user classes can perform with respect to the system. • Use cases that development approach can use it because the user doesn't care how the software is built.

11. 2. The Use-Case Approach • 2.1 use cases • Use cases are at the center of the widely used Unified Software Development Process. • Use cases shift the perspective of requirements development to discussing what users need to accomplish, in contrast to the traditional elicitation approach of asking users what they want the system to do.

12. Employee object class (UML)

13. 2. The Use-Case Approach LIBSYS use cases • 2.2 Use-case diagrams • Partial use-case diagram for the LIBSYS system . 13

14. 2. The Use-Case Approach Use-cases for the weather station

15. 4. References Software Requirements, Second Edition , Karl E.Wiegers. Software Engineering , 8th Edition , lan sommerveill . 15

16. Thank You ! Supervisor: Eng : Tasneem Darwish. Done by: Ramy Y. Baraka