BUS 362 Lecture Notes - Lecture 6: List Of Fables Characters, Use Case, Business Process

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Chapter 4: Use Case Analysis
Used cases - used to explain and document the interaction between the user and the system to
accomplish user’s task.
Represents how a system interacts with its environment by illustrating the activities that are performed
by the user and the system’s responses.
The goal is to create asset of use cases that describe all the tasks that users need to perform with the
system
Use cases describe the system’s activities from the user’s perspective in words, user involvement is
essential
Created to help the development team understand the steps in accomplishing the users’ requirements.
Once created - used to derive more detailed functional requirements for the new system.
Also helpful in understanding exceptions, special cases, and error handling requirements in new system.
They don’t capture the internal working of the software system or its complexity
Text based use case is easy for the users to understand
oFlows easily to create of process models and data models
oHelps in the testing the system created
The use case approach is the same for the as-is system and the to- be system but the focus is different
oAs-is model focus on current business processes
oTo-be model focuses on desired business processes
Business processes
A business process describes a set of activities that are necessary to complete a response to a stimulus
applied to an organization
oUnit of work
Routine business processes:
ofulfill customer order
oreceive shipment for inventory
oreview loan applications
ocreate a two-week payroll
oMore complex business processes:
oDeveloping a new product
oDeciding on a location for new store
oDesigning a new marketing campaign
The stimulus for an organization to respond to could be external:
ocustomer request
osupplier shipment
onew knowledge about competitor
or from an internal source:
omanagement wants new product developed
oorganization opening a new branch office
What is a Use Case?
Use case - depicts a set of activities performed to produce some output result
Each use case describes how an external user triggers an event to which the system must respond
With this type of event-driven modeling, everything in the system can be thought of as a response to
some triggering event
oWhen there are no events to trigger the system, the system is waiting
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When a trigger event occurs, the system responds, performs an action define in the use case and then
returns to waiting state
We create use cases when they are likely to help us better understand the requirements
oFor very simple processes we don’t need a use case
Creation of use cases is often done as a part of interview session with users or a part of JAD sessions –
in complex situations
Elements of a Use Case
Basic Information
oEach use case has a name and number and a brief description (conveys purpose)
oThe priority may be assigned to indicate the relative significance
oThe actor/user role refers to a person, another system, or a hardware device that interacts with
the system to achieve a useful goal
oThe trigger for the use case – the event that causes the use case to begin
External Trigger – initiated by an external actor” (person, role, another system) e.g.
customer placing an order
Temporal Trigger – initiated by passage of time or where the event is time-based e.g.
weekly payroll
Preconditions
oCommon practice to create small, focused use cases breaking the whole process down into parts
oImportant to define clearly what needs to be accomplished before each use case begins
for example, a ‘sign in’ use case would require that a customer has an account. If not, it
would direct them to a ‘create account’ use case
oThe preconditions define the state the system must be in before the use case commences
oImportant to know what state the system is in before use case begins
Normal Course
oDescription of the major steps that are performed to execute the response to the event, the inputs
used for the steps, and the outputs produced
oThe normal course lists the steps – “birds eye perspective” describes what the outsider could
observe while watching the user and system interact
oThe steps are listed in the order they are performed
oNo exceptions exist
Alternative courses
oAre included to show branches in logic that also will lead to successful conclusion of the use
case
owhat happens if some alternative event takes place?
‘sign up’ would be an alternative course in our eBay log in example
Post conditions
oan inventory of the results of progressing successfully through the use case
oThe post conditions section defines the final product of the use case
oThese post conditions also serve to define the preconditions for the next use case in the series
oImportant to know what state the system is in when the use case is completed
Exceptions
oDescribe any error conditions or exceptions that may occur as the use case steps are performed
oNot normal branches in decision logic but are unusual occurrences of errors that could be
encountered and will lead to an unsuccessful result.
Ensure the system will not fail when in use due to errors nobody thought about – better to
identify trouble during the analysis so avoid error during testing and implementation
Summary inputs and outputs
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