Use Case - Sheridan

Report
SYST39409 - Object Oriented Methodologies
OBJECT ORIENTED
METHODOLOGIES
J.N.Kotuba
Week02
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Agenda
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Assignment No 1 posted
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
Review details
SLATE-Weekly Topical Outline and Schedule modified
Recap last lesson
Learning outcomes for today
 Develop
the requirements model & the Unified
Process
 Use cases
 Use case diagrams
 Use case narratives
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Last Class
3
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Introduced Unified Modeling Language (UML)
Discussed
Models
 Tools
 Techniques
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Context Diagram –Pharmacy System
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Objectives for today
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Explain the difference between the Waterfall SDLC
and the unified process
Learn how to use the Event Table Technique to
identify use cases
Learn how to construct a use case diagram
Learn how to build a use case narrative for each
use case and why the narratives are important
Be able to explain the difference between the
system boundary and the automation boundary
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
The Unified Process
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
Four key stages.
 Inception.
 Elaboration
 Construction
 Transition
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Unified Process:Inception
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Go ahead on project.
Scope determined.
Business case developed for project.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Unified Process: Elaboration
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Basic architecture of the system developed.
Construction plan is approved.
Risks are identified.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Unified Process: Construction.
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Iterative approach to developing software.
Product will be a beta.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Unified Process:Transition
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Beta product is introduced to users and information
is collected from users during roll-out.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Iterative Development
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Modeling
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Software development is the production of
‘executable models’.
These models often are abstractions of the original
problem with classes added to solve the user’s
problems.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Different Types of Models
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Use Case Model. The system from the users point of
view.
Static Model. The elements of the system and how
they relate to one another.
Dynamic Model. Outlines the behaviour of the
system in the context of Object interactions.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
UML
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The Unified Modeling language is (UML) a
language for development object-oriented models
and system designs.
It provides a complete set of graphical diagrams to
specify use cases, class diagrams and the dynamic
model (object interactions) of a system.
Can be used with different programming
languages.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
System Boundary vs Automation Boundary
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
System Boundary vs Automation Boundary
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Model
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A use case is a script:
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A step-by-step description
of how a user might make
use of the system to do a
task
It is a “case of the usage
of the system.”
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User Goals, Events, and Use Cases
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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
 Each
goal at the elementary business process (EBP) level is a
use case
 EBP
– a task performed by one user, in one place in response
to a business event, that adds measurable business value, and
leaves system and data in consistent state
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User Goals, Events, and Use Cases
(continued)
 CRUD
 Event
analysis technique (create, read, update, delete)
decomposition technique
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Identifying Use Cases Based on User
Goals
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Use Case Based on CRUD Technique
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CRUD Matrix Example
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SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Discovering Use Cases
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Event – in the real world
Event occurs when something happens
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Events drive or trigger all processing that a system does.
 What events occur that will affect the system being studied?
 What events occur that will require the system to respond in some
way?
Black Box view – focus on “what” not “how”
SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Event Decomposition Technique
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Event – an occurrence at a specific time and place
and which needs to be remembered
Business events trigger elementary business processes
(EBPs)
EBPs are at correct level of analysis for use cases
Identify business events to decompose system into
activities/use cases
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Types of Events

External
 Outside
system
 Initiated by external agent or actor
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Temporal
 Occur
as result of reaching a point in time
 Based on system deadlines
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State
 Something
inside system triggers processing need
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Events – (affecting a system)
External event checklist
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SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Temporal Event Checklist
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SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Listing events
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When analyzing a system we must list all events
Identify other information about each of them
SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Identifying Events
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Can be difficult to determine
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Often confused with conditions and responses
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May be useful to trace a transaction’s life cycle
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Certain events left to design phase
 System
controls to protect system integrity
 Perfect
technology assumption defers events
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Sequence of Actions that Lead Up to Only One Event
Affecting the System
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Sequence of “Transactions”
for One Specific Customer
Resulting in Many Events
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Events Deferred Until the Design
Phase
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Event table
“Process”  Use Case
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SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Event Table Exercise- Pharmacy System
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Identifying the Actors
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Where do you look?
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Context Diagram
Existing system documentation (our case)
Ask the following questions
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Who or what provides inputs,such as forms, voice commands, fields on input
screens, etc to the system?
Who or what receives outputs, such as email notifications, reports, voice
messages , etc from the system?
Are interfaces required to other systems?
Are there any events that are automatically triggered at a predetermined
time?
Who (User) will maintain the information system?
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case - Actors
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An actor is always outside the automation boundary of the
system but may be part
of the manual portion of the system
an actor is not always the same as
the source of the event in the event table.
A source of an event is the initiating person,
such as a customer, and is always external to the system,
including the manual system.
an actor in use case analysis is the person who is actually
interacting (hands-on) with the computer system itself.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Identifies What Users Want
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
Use cases focus on usage of the system
 Services
 Behaviors
 Responses
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No internal structural details of the system
Can be considered as the “responsibilities” of the
system
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Identifies What Users Want
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Next
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Validate use case names
Write narrative
descriptions for each
use case
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Refining the name
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May “discover” more than
one use case
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E.g register member
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Purchase
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SYST39409 - Object Oriented Methodologies
Register new member
Renew existing
member
Retail
Trade
Dealer
staff
J.N.Kotuba
Use Case Identifies What Users Want
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Refining the name
 Does
it tell the whole story?
 Any exceptions?
 Special cases?
 Possible errors?
 Occasional variations?
 Does the name cover several related or similar
processes?
 Is there a more informative or enlightening name?
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Identifies What Users Want
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Write a narrative description
 Sequence
 Focus
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of events or steps user goes through.
on mainline
Straight-line sequence
Then consider exceptions, options errors
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Cases
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
Analysts define use cases at three levels
 Brief
 Intermediate
 Fully
developed
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Narrative:
Fill Prescription
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Step 1.Pharmacist inputs Patient ID
Step 2.System displays patient medical record
Step 3.Pharmacist verifies dosage, potential allergic reactions and/or interaction with
other medications.
Step 4.The Pharmacist fills the prescription and updates the patient’s medical record on
the system with details of the new prescription.
Step 5. The system prints a label which is sent to the nurses station and the Billing Dept.
is given Patient and Prescription details.
Alt Step 3. If the pharmacist determines a possible negative condition exists, then the
Doctor is contacted
Alt Step 4. The prescription is held for disposition and the process terminates with the
pharmacist proceeding to the next prescription in the queue.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Brief Description of Create New Order Use Case
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Intermediate Description of Telephone Order Scenario for Create New
Order Use Case
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Fully Developed Description of Telephone Order Scenario for Create New Order
Use Case
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Narratives- Preconditions & Post
Conditions
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Hospital Pharmacy Case Study
SYST39409-Object Oriented Methodologies
© Jerry Kotuba
Example
“Review
Prescription”
Use Case
Fully Developed
Package:
Pharmacy System
Use Case Name:
Review Prescription
Primary Actor:
Pharmacy Technician
Other Participating Actors:
Summary Description:
When prescriptions are received at the Mercy Hospital Pharmacy, they are directed to the
Pharmacy Technician. He reviews the prescription and then decides, based on the type of
medication, which of three stations to direct it to for filling.
Preconditions:
The prescription must be for a current patient of Mercy Hospital and issued by a licensed
Medical Doctor.
Trigger:
Prescription is received by the pharmacy.
Typical Course of events:
1.
2.
3.
4.
5.
Pharmacy Technician (PT) verifies that the patient is an admitted patient.
PT verifies that a licensed Medical Doctor issued the prescription.
PT logs the prescription into the system and it is assigned a serialized ID number by the
system.
PT checks the type of medication; if it must be formulated (made-on-site), sends it to the
lab station; if it is an off-the-shelf medication, sends it to the shelving station; narcotics
are sent to the secure station.
PT enters the shelving station ID to which it was sent into the system.
Alternative Paths:
If the patient is not currently admitted to the Hospital, the prescription is returned to the Doctor.
If the Doctor is not listed in the Pharmacy database, the prescription is referred to the
Pharmacist for disposition.
Post conditions:
The prescription is assigned to a filling station and logged into the system for tracking.
Assumptions:
Related Business Rules:
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Author:
Date:
Prescriptions can only be accepted from licensed Physicians for patients admitted to Mercy
Hospital.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
May 2012
J.N.Kotuba
Use Case Narrative:
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Do’s
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Use complete sentences
How is the use case
initiated and how does
it end
What the initial and
final actions and state
of the system look like

Don’ts
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SYST39409 - Object Oriented Methodologies
Use abbreviations or
sentence fragments
J.N.Kotuba
50
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Components of the Use Case Diagram
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Use Case
Actor
System Boundary
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Draw the Use Case with SA
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SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Your Turn…
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
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See SLATE – I-C-E-01
Use Case For the Dental Office Appointment
System, develop;
 Context
Diagram
 Event table
 Use Case Diagram
 Create a narrative for each use case (Intermediate Level)
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Use Case Guidelines

Names

Noun + Verb
J.N.Kotuba
SYST39409 - Object Oriented
Methodologies
54
Use Case Guidelines

J.N.Kotuba
Nouns
SYST39409 - Object Oriented
Methodologies
55
Use Case Guidelines

Avoid using implementation system
specific language when writing use
case narratives
J.N.Kotuba
SYST39409 - Object Oriented
Methodologies
56
.Summary Developing the Requirements Model:
The Use Case Model
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Use Cases are an informal description of the system;

They do not give information about how the system does things

Or any other details internal to the system.
They just tell us
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what the system will do for the users.
Concentrating on what rather than how makes them more a tool for analysis
than design, but. . .
They do give us a good starting point for both
 Testing the system, and
 Prototyping the user interface.
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
Recap Lesson
58

Learning outcomes for today
 Develop
the requirements model
 Use cases
 Use case diagrams
 Use case narratives
SYST39409 - Object Oriented Methodologies
J.N.Kotuba
What Comes Next?
59
SYST39409 - Object Oriented Methodologies
J.N.Kotuba

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