USE CASE ANALYSIS AND DIAGRAMMING

Group 1

Regina Shakespeare

Ornella Dunn

Odaine McMillan

Sherece Doyley

Courtney Francis

Objectives

Define Case and Use Case Diagramming

The Purpose of a Use CaseThe Elements of a Use CaseContribution to the Identification of

functional requirementsConstruct a Use Case Diagram

What is a Use Case?

A use case is a form of technique used in system analysis. It is used to identify, clarify, and organize system requirements.

A use case diagram is a simple representation of the users/actors' interaction within the case system.

What Does It Entail?

It consists of a group of elements that can be used together in a way that will have an effect larger than the sum of the separate elements combined.

The elements are, the actor, the use case, the system boundary, & system association. In some cases it may also consist of, extend and include elements.

What Does It Entail ? (cont’d)

The use case should contain all system activities that have significance to the users.

What is the Purpose of a Use Case?

Used to gather requirements of a system.

Used to get an outside view of a system.

Identify external and internal factors influencing the system.

What is the Purpose of a Use Case? (cont’d)

Records paths from trigger events to goals

Describes one main flow of events (also called a basic course of action), and possibly other ones, called exceptional flows of events (also called alternate courses of action)

Purpose of Use Case in the Analysis Stage of the SDLC

The analysis stage of the system development life cycle involves determining the end user requirements.

The purpose of the Use Case diagram is to show the various activities the users can perform using the information system .

Example of a Use Case Diagram

Elements of a Use Case

Actor

Use Case

System Boundary

An Association Relationship

The Actor

What is an Actor?

An actor portrays any entity (or entities) that perform certain roles in a given system.

The different roles the actor represents are the actual business functions of users in a given system.

An actor in a use case diagram interacts with a use case.

For example, for modeling a visa application at the embassy, a customer entity represents an actor in the application.

Also the receptionist who processes the applications at the counter is also an actor.

However decision resides with you to determine what actors make an impact on the functionality that you want to model.

If an entity does not influence the any function of the process you are modeling, it cannot be represented as the actor.

System Boundary

A system boundary defines the scope of what a system will be and/or its intended function.

A system boundary in a use case diagram also describes the limits and restrictions of the system.

The system boundary is shown as a rectangle spanning all the use cases in the system.

This drawing depicts the system boundary of a visa application. The use cases of this system are enclosed in a rectangle. Note that the actors in the system are outside the system boundary.

Association Relationship

Use cases share different kinds of relationships. A relationship between two use cases is basically a dependency between the two use cases.

Use case relationships can be one of the following:

• Include• Exclude

Include Relationship

An include relationship, includes the functionality described in another use case as a part of its business process flow.

An include relationship is depicted with a directed arrow having a dotted shaft. The tip of the arrowhead points to the child use case and the parent use case is connected at the base of the arrow.

Example of Include RelationshipFor example, you can see that the functionality defined by the "Validate Application" use case is contained within the "Make appointment" use case.

Hence, whenever the "Make appointment" use case executes, the business steps defined in the "Validate Application" use case are also executed

Extend

In an extend relationship between two use cases, the child use case adds to the existing functionality and characteristics of the parent use case.

An extend relationship is depicted with a directed arrow having a dotted shaft, similar to the include relationship.

Extend

The tip of the arrowhead points to the parent use case and the child use case is connected at the base of the arrow.

The figure shows an example of an extend relationship between the "Perform medical tests" (parent) and "Perform Pathological Tests" (child) use cases.

The "Perform Pathological Tests" use case enhances the functionality of the "Perform medical tests" use case.

The "Perform Pathological Tests" use case is therefore a specialized version of the generic "Perform medical tests" use case.

Use Case Contribution to the Identification of Functional Requirements

The purpose of use-case is to reveal the functional requirements of a system.

Functional requirements captures the behaviour of the system.

It focuses on what an existing system does or new system should do and NOT how the system delivers or should deliver those functions.

Use Case Contribution to the Identification of Functional Requirements

The use-case modeling is done in the early stages of systems development to help developers to clearly understand the functional requirements.

The use case contains all system activities that have significance to the users.

Developers need to involve the users in discussions throughout the model development process to finally make an agreement on the requirements specifications.

Use Case Contribution to the Identification of Functional Requirements

When used to model functional requirements, a use case describes one function required of your system or application.

As such, your use cases constitute a functional specification.

Use Case Contribution to the Identification of Functional Requirements

GoalBusiness Requirement –

“increase profit”

Use CaseUser Requirement – “Create

purchase order”

The use case can be thought of as a collection of possible scenarios related to a particular goal or problem and is initiated by the user.

Use Case Contribution to the Identification of Functional Requirements

Goal

Business Requirement – “increase profit”

Use CaseUser Requirement – “Create

purchase order”

Functional Requirements“calculate profit maximizing

price”

A user’s view is transformed into the developer’s view by creating functional requirements

Use Case Contribution to the Identification of Functional Requirements

Some goals of doing requirements: understand precisely what is

required of the software communicate this understanding

precisely to all development parties control production to ensure that

system meets specs (including changes)

DEMONSTRATION