Object-oriented modelingModeling the functions and
dynamics of the systemUse case diagram
Karolina Muszyńska
Based on: http://www.csun.edu/~dn58412/IS431/IS431_SP13.html G. Schneider , J.P. Winters „Stosowanie przypadków użycia” S. Wrycza, B. Marcinkowski, K. Wyrzykowski „Język UML 2.0 w modelowaniu
SI”
Why Object Modeling? Genesis of UML UML diagrams Use Case Diagrams From business tasks to Use Cases
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Object Modeling
Object modeling is a technique for identifying objects within the systems environment and the relationships between those objects.
Object-oriented analysis (OOA) techniques are used to (1) study existing objects to see if they can be reused or adapted for new uses, and (2) define new or modified objects that will be combined with existing objects into a useful business computing application.
The Unified Modeling Language (UML) is a set of modeling conventions (notations) to specify or describe a software system in terms of objects.
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Object Modeling
Benefits:◦ Break a complex system into manageable
components◦ Create reusable components can be plugged
into other systems or use them as starting points for other projects
◦ “Object-think” is more realistic !!!
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Object Modeling
Methodological storm in object-oriented solutions (1989-94)◦ over 50 various object-oriented methods/solutions
Unified Modeling Language (UML)◦ Third generation OO method◦ An attempt to combine advantages of previous
methods Basis for the UML standard
◦ Object Modeling Technique (J. Rumbaugh) – UML diagrams notation, analysis and design
◦ Object Oriented Analysis and Design (G. Booch) – analysis and design
◦ Object Oriented Software Engineering (I. Jacobson) – business modeling, use cases
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Genesis of UML
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UML Diagrams
Structure diagrams. A type of diagram that depicts the elements of a specification that are irrespective of time. This includes class, object, package, composite structure diagrams and implementation diagrams: component and deployment diagrams.
Behavior diagrams. A type of diagram that depicts behavioral features of a system or business process. This includes activity, state machine, and use case diagrams as well as the four interaction diagrams.
Interaction diagrams. A subset of behavior diagrams which emphasize object interactions. This includes sequence, communication, interaction overview, and timing diagrams.
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UML Diagrams
Modeling the functions of the system (with a use case diagram).
Modeling the objects within the scope of the system and their relationships (with class and object diagrams for each use case, and then for the integrated system).
Modeling the interactions between objects to complete a function/use case (with a sequence diagram and activity diagram for each use case).
Modeling the behavior / logic of the objects (with a statechart diagram for each complex class).
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Most common UML Diagrams
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UML Diagrams
STATECHART DIAGRAM FOR OBJECT “Order”
Enter New Customer
Create New Order
:customer :order
Create Order
SHIP ORDERCREATE ORDER
ORDER
CUSTOMER
SHIPMENT
USE CASE DIAGRAM CLASS DIAGRAM FOR USE CASE
“Create New Order”
SEQUENCE DIAGRAM
FOR USE CASE “Create
New Order”
Order Clerk
Order Clerk
:shipment
Create Shipment
Use case modeling is the process of modeling a system’s functions in terms of business events, who initiated the events, and how the system responds to the events.
A use case is a complete sequence of related actions (a scenario), both automated and manual, for the purpose of completing a business function: What the system must do.
An actor represents an external entity that needs to interact with the system to exchange information. An actor is a user, a role, which could be an external system as well as a person.
A temporal event is a system event that is triggered by time. (The actor of a temporal event use case is time.)
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Use Case Modeling
Use Case Diagram is a functional description (use cases, actors) of the entire system: functions being supported by the system
Use Case Diagram does NOT indicate data flows or flows of information in and out the system (they are identified later in interaction diagrams)
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USE CASE DIAGRAM
An extension use case extends the functionality of an original use case to add new behaviors or actions to the basic course. An extension use case can only be invoked by the use case it is extending.
An abstract use case contains typical course steps that were common to two or more original use cases. An abstract use case reduces redundancy and promotes reuse.
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Extension and Abstract Use Cases
“Class registration” is the basic course of actions.
On special occasions, “Registration for special classes” and/or “Insufficient prerequisites” will be invoked.
Special cases add new data/behaviors to the normal case.
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Extension Use Cases(“extend” relationship)
<<extend>> <<extend>>
Class registration
Registration for special classes
Insufficient prerequisites
“Track sales & inventory” includes “Reorder Supplies” and “Generate reports”
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Abstract Use Cases (“include” relationship)
<<include>>
<<include>>
Track sales & inventory
Reorder supplies
Generate reports
“Place order by telephone” or “Place order via webpage” are possible types of “Place order”
“Sales Representative” plays all roles of “Client”
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Inheritance among Actors or Use Cases
Place order
Place order by telephone
Place order via webpage
Client
Prepare sales reportSales
Representative
CRUD (Create, Read, Update, Delete) type use cases are used when application is meant to store data and one actor interacts with it (e.g. database maintenance, order management, etc.).
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CRUD Use Cases vs. Individual Use Cases
Place order
Check order status
Cancel order
Client
Administer warehouse state DataBase
Administrator
Salesman
Each use case should include documentation in the form of scenarios
Scenario is a sequence of actions documenting a behavior
Each use case should have at least the main scenario but it is preferable to include the alternative scenarios as well
Both main and alternative scenarios precisely describe the full functionality represented by a use case
Additional important elements of the use case documentation include: pre-conditions and post-conditions
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Use Case Documentation
Identify actors (look at the sources and destinations of major inputs and outputs)
Identify use cases (major system functions)
Identify the system boundary
Identify associations between actors and use cases
Identify additional associations between use cases (“extend”, “include”)
Identify inheritance relationships among use cases and actors
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Building a Use Case Diagram
From business tasks to Use Cases
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Business task description
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Use case diagram
1. Service personnel selects 'Make repair reservation‘2. System displays 'repair reservation' form3. Service personnel selects client search 4. System displays list of clients5. Service personnel chooses a client6. System inserts the client's data into the 'repair
reservation' form7. Service personnel selects repairs search 8. Include: Display repair types9. Service personnel selects the repair type10. System inserts the repair's data together with the cost
to the 'repair reservation' form 11. Service personnel selects 'make repair reservation‘12. System displays confirmation
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„Make repair reservation” use case specification
before point 5. extend: Add client
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„Make repair reservation” use case extension point
„Add client” use case specification
1. System displays 'add client' form2. Service personnel inserts client's data (name, address,
phone number, e-mail address)3. Service personnel selects 'add client‘4. System displays confirmation
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Rent-a-Car case study Possible business tasks:
Rent a car
Take back the rented car
Prepare cars for rental
Make a reservation for a car
Buy a car
Sell a car
…
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„Rent a car” business task
Business steps:
Identifying the type of car and rental time frame the client is interested in
Identifying the client
Preparing the rental contract
Signing the contract and informing garage about new rental