Defining system requirements

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Defining system requirements

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• Defining System Requirements• CRUD Operations• Events and Use Cases

Lecturer details

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SDLC Activities

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Techniques for Identifying Use Cases1- 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

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• Involves a variety of models to document requirements

• Two key concepts identifying functional requirements

Use cases and the events that trigger them

Things in the users’ work domain

Define system requirement

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• 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

1. Use Case concept / User goal technique

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Four operations with data:

Create

Read

Update

Delete

2. Use Case concept / CRUD technique

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• 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

Use case Description

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Example

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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”)

3. Events and event types

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Events and Use Cases in Account Processing

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Identifying an Event

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• 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

Documenting an event

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Documenting an event example

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End

Thank you

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