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CIS320
Systems Analysis and Integration

Week 1 – Use Cases

Systems Analysis and Design in a Changing World, 6th Edition

Chapter 3

Overview
This chapter focuses on identifying and modeling the key aspect of functional requirements– use cases
Outline
Use Cases and User Goals
Use Cases and Event Decomposition
Use Cases and CRUD
User Case Diagrams

Systems Analysis and Design in a Changing World, 6th Edition

Use Cases

Use case— an activity that the system performs, usually in response to a request by a user
Use cases define functional requirements
Analysts decompose the system into a set of use cases (functional decomposition)
Two techniques for Identifying use cases
User goal technique
Event decomposition technique
CRUD technique is used for validating, cross-checking
Name each use case using Verb-Noun

Systems Analysis and Design in a Changing World, 6th Edition

User Goal Technique

This technique is the most common in industry
Simple and effective
Identify all of the potential categories of users of the system
Interview and ask them to describe the tasks the computer can help them with
Probe further to refine the tasks into specific user goals, “I need to Ship items, Track a shipment, Create a return”

Systems Analysis and Design in a Changing World, 6th Edition

User Goal Technique
Some RMO CSMS Users and Goals

Systems Analysis and Design in a Changing World, 6th Edition

User Goal Technique:
Specific Steps

Identify all the potential users for the new system

Classify the potential users in terms of their functional role (e.g., shipping, marketing, sales)

Further classify potential users by organizational level (e.g., operational, management, executive)

For each type of user, interview them to find a list of specific goals they will have when using the new system (current goals and innovative functions to add value)

Systems Analysis and Design in a Changing World, 6th Edition

User Goal Technique
Specific Steps (continued)

Create a list of preliminary use cases organized by type of user

Look for duplicates with similar use case names and resolve inconsistencies

Identify where different types of users need the same use cases

Review the completed list with each type of user and then with interested stakeholders

Systems Analysis and Design in a Changing World, 6th Edition

Event Decomposition Technique

More Comprehensive and Complete Technique
Identify the events that occur to which the system must respond.
For each event, name a use case (verb-noun) that describes what the system does when the event occurs
Event– something that occurs at a specific time and place, can be described, and should be remembered by the system

Systems Analysis and Design in a Changing World, 6th Edition

Events and Use Cases

Systems Analysis and Design in a Changing World, 6th Edition

Types of Events

External Event
an event that occurs outside the system, usually initiated by an external agent or actor
Example: Customer places an order
Temporal Event
an event that occurs as a result of reaching a point in time
Example: It’s month’s end and the expense report needs to be printed
State Event
an event that occurs when something happens inside the system that triggers some process
Example: reorder point is reached for inventory item

Systems Analysis and Design in a Changing World, 6th Edition

Event Decomposition Technique:
Specific Steps

Consider the external events in the system environment that require a response from the system by using the checklist shown in Figure 3-3

For each external event, identify and name the use case that the system requires

Consider the temporal events that require a response from the system by using the checklist shown in Figure 3-4

For each temporal event, identify and name the use case that the system requires and then establish the point of time that will trigger the use case

Systems Analysis and Design in a Changing World, 6th Edition

Event Decomposition Technique:
Specific Steps (continued)

Consider the state events that the system might respond to, particularly if it is a real-time system in which devices or internal state changes trigger use cases.

For each state event, identify and name the use case that the system requires and then define the state change.

When events and use cases are defined, check to see if they are required by using the perfect technology assumption. Do not include events that involve such system controls as login, logout, change password, and backup or restore the database, as these are put in later.

Systems Analysis and Design in a Changing World, 6th Edition

Event Decomposition Technique: Benefits

Events are broader than user goal: Capture temporal and state events
Help decompose at the right level of analysis: an elementary business process (EBP)
EBP is a fundamental business process performed by one person, in one place, in response to a business event
Uses perfect technology assumption to make sure functions that support the users work are identified and not additional functions for security and system controls

Systems Analysis and Design in a Changing World, 6th Edition

Use Cases and CRUD Technique

CRUD is Create, Read/Report, Update, and Delete (archive)
Often introduced in database context
Technique to validate, refine or cross-check use cases
NOT for primarily identifying use cases

Systems Analysis and Design in a Changing World, 6th Edition

Use Case Diagrams

Use case diagram— a UML model used to graphically show uses cases and their relationships to actors
Actor is the UML name for a end user
Automation boundary— the boundary between the computerized portion of the application and the users who operate the application

Systems Analysis and Design in a Changing World, 6th Edition

Use Case Diagram - Example

Systems Analysis and Design in a Changing World, 6th Edition

Use Case Diagrams
The <<Includes>> relationship

A relationship between use cases where one use case is stereotypically included within the other use case— like a called subroutine. Arrow points to subroutine

Systems Analysis and Design in a Changing World, 6th Edition

Use Case Diagrams:
Steps

Identify all the stakeholders and users who would benefit by seeing a use case diagram
Determine what each stakeholder or user needs to review in a use case diagram: each subsystem, for each type of user, for use cases that are of interest
For each potential communication need, select the use cases and actors to show and draw the use case diagram. There are many software packages that can be used to draw use case diagrams
Carefully name each use case diagram and then note how and when the diagram should be used to review use cases with stakeholders and users

Systems Analysis and Design in a Changing World, 6th Edition

Summary

Use cases are the functions identified, the activities the system carries out usually in response to a user request
Two techniques for identifying use cases are the user goal technique and the event decomposition technique
The user goal technique begins by identifying end users called actors and asking what specific goals they have when interacting with the system
The event decomposition technique begins by identifying events that occur that require the system to respond.
The CRUD technique is used to validate and refine the use cases identified

Systems Analysis and Design in a Changing World, 6th Edition