Defining system requirements

1. Defining system requirements

2. Lecturer details • Defining System Requirements • CRUD Operations • Events and Use Cases

3. SDLC Activities

4. Techniques for Identifying Use Cases 1- user goal technique • Analyst talks to all users to get them to describe their goals in using the system 2- CRUD technique • Analyst looks at each type of data and includes use cases that create the data, read or report on the data, update the data, and delete the data 3- elementary business process (EBP) • a task that is performed by one person, in one place, in response to a business event; it adds measurable business value and leaves the system and its data in a consistent state • event decomposition technique

5. Define system requirement • Involves a variety of models to document requirements • Two key conceptsidentifying functional requirements • Use cases and the events that trigger them • Things in the users’ work domain

6. 1. Use Case concept / User goal technique • Use Case -- An activity the system performs in response to a user request • Techniques for identifying use cases • User goal technique – by talking to users to get their description of goals in using the system

7. 2. Use Case concept / CRUD technique • Four operations with data: • Create • Read • Update • Delete

8. Use case Description • Use case description – a description of the processing steps for a use case • Actor – a person or thing that uses the system and interacts with the system • Scenario or Instance – a particular set of internal steps/activities to complete a business process • Preconditions – conditions that must be true before a use case begins • Postconditions - conditions that must be true upon completion of the use case

9. Example

10. 3. Events and event types • Event – an occurrence at a specific time and place which requires system to respond • External • Outside system • Initiated by external agent or actor (e.g., “Customer places an Order”) • Temporal • Occur as result of reaching a point in time (not external) • Based on system (e.g., “Produce a biweekly payroll”)

12. Events and Use Cases in Account Processing

13. Identifying an Event

14. Documenting an event • Event table represents events and their details • Trigger: an occurrence that tells the system that an event has occurred • Source: an external agent or actor that supplies data to the system • Activity: behavior that the system performs when an event occurs • Response: an output, produced by the system that goes to a destination • Destination: an external agent or actor that receives data from the system

15. Documenting an event example

16. End Thank you ??????