Use Cases & Requirements Analysis By: Mostafa Elbarbary

Objectives Define software Requirements and their types Define actor, use case, and use-case model Explain Software Requirements Engineering Process Explain how use cases fit into a requirements engineering process

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Requirements Requirements are capabilities and conditions to which the system conform.

Requirements Types Functional Requirements functional requirement defines a function and features of a software system or its component. Non Functional Requirements Usability, Reliability, Performance, Security,etc.

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Use cases and Requirements Use cases are requirements, primarily functional or behavioral requirements that indicate what the system will do. Use cases Used to capture and model Functional requirements.

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Use Case Elements A Use Case is a collection of related success and failure scenarios that describe an actor using a system to support a goal. A scenario is a specific sequence of actions and interactions between actors and the system; it is also called a use case instance

Use Case Elements An actor is something with behavior, such as a person (identified by role), computer system, or organization; for example, a Student. Actors Type Primary actor has user goals fulfilled through using services of the SuD. Supporting actor provides a service (for example, information) to the SuD.

An Example Process Sale Handle Returns Cashier Partial Use case diagram for Point of Sale System Tax Calculator

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Use case Relationships Includes relationship allows one use case to use the functionality provided by another use case > Login

An Example Student Submit Class Schedule Register for Classes > Login Administrator > Partial Use case diagram for University Management System

Use case Relationships Extends relationship allows one use case the option to extend the functionality provided by another use case >

An Example Customer Cash Deposit Cash Withdrawal > Login > Partial Use case diagram for ATM Print Receipt >

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Use Case Model Use cases are text documents, not diagrams, and use-case modeling is primarily an act of writing text, not drawing diagrams. The Use-Case Model may optionally include a UML use case diagram to show the names of use cases and actors, and their relationships.

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Use Case Formats Brief Terse one-paragraph summary, usually of the main success scenario. Register for Classes: Student Requests Classes’ Section for a Term. System Adds the student to each section if possible. On completion, the student receives list of classes he is enrolled in.

Use Case Formats Casual Informal paragraph format. Multiple paragraphs that cover various scenarios. Register for Classes: Student Requests Classes’ Section for a Term. System Adds the student to each section if possible. On completion, the student receives list of classes he is enrolled in. if Invalid section number entered. Indicate error.

Use Case Formats fully dressed All steps and variations are written in detail, and there are supporting sections, such as preconditions and success guarantees. Use CaseRegister for Classes ActorsStudent PurposeRegister student for classes and record the student’s schedule OverviewStudent Requests Classes’ Section for a Term. System Adds the student to each section if possible. On completion, the student receives list of classes he is enrolled in. Pre-ConditionsClass schedule must exists Student is known by the system Post-ConditionsStudent was enrolled in the section

Main Success Scenario 1. Student desires to register for class 2. Student provides ID, Course number and section no. 3. Adds the student to the section if there are seats available 4. On completion of Entry, Student submits. 5. Produces a student class list for the student. 6. Student receives the class list Alternative Scenario 3a 1.Invalid section number entered. Indicate error. Return to step 2. 3b 1.No seats remaining. Inform the student. Return to step2 Use Case Formats

Agenda Requirements and Requirements Type Use cases and Requirements Use case Elements Use case Relationships Use case Model Use case Formats Use case Types Use Cases and Requirements Analysis

Use Case Types Business (Essential) Use Case describes the interaction between the user and the system at a high level of abstraction. System (Concrete) Use case the interaction between the user and system in a more detailed way

Use Case and Requirements Analysis 1. Identify the primary actors and their goals 2. Identify the use cases and make a use case diagram for the system. 3. Write a use case narrative describing use case main success scenario (Brief Format). 4. Detail use case narrative describing use case main success scenario and Alternative scenarios(Fully- dressed Format).