1. Chapter 2: Modeling with UML - 2

2. A Medical Clinic Example
“A patient calls the clinic to make an appointment for a yearly checkup. The receptionist finds the nearest empty time slot in the appointment book and schedules the appointment for that time slot”
“A patient can request or discuss medication with a doctor”
“A patient can make payment through the system”
<includes>, <extends>, generalization
Online tutorial and Use case modeling tips

3. Use Case Diagrams: Summary
Use case diagrams represent external behavior
All use cases need to be described for the model to be useful.
An Actor is a role of an object or objects outside of a system that interacts directly with it as part of a coherent work unit (a use case)
<<includes>> and <<extends>> allow common fragments of use cases to be pulled out into a separate use cases
<<includes>> is like a “use case subroutine”
<extends>> is an alternative course of action

4. Class Diagrams
TarifSchedule
Trip
Enumeration getZones()
Price getPrice(Zone)
zone:Zone
Price: Price * *
Class diagrams represent the structure of the system.
Used
during requirements analysis to model problem domain concepts
during system design to model subsystems and interfaces
during object design to model classes.

5. Classes Name Signature Attributes Operations
Table zone2price
Enumeration getZones()
Price getPrice(Zone)
TarifSchedule
Name
zone2price
getZones()
getPrice()
TarifSchedule
Attributes
Signature
Operations
TarifSchedule
A class represent a concept
A class encapsulates state (attributes) and behavior (operations).
Each attribute has a type.
Each operation has a signature.
The class name is the only mandatory information.

6. tarif_1974:TarifSchedule
Instances
tarif_1974:TarifSchedule
zone2price = {
{‘1’, .20}, {‘2’, .40},
{‘3’, .60}}
An instance represents a phenomenon.
The name of an instance is underlined and can contain the class of the instance.
The attributes are represented with their values.

7. Actor vs Instances
What is the difference between an actor , a class and an instance?
Actor:
An entity outside the system to be modeled, interacting with the system (“Passenger”)
Class:
An abstraction modeling an entity in the problem domain, must be modeled inside the system (“User”)
Object:
A specific instance of a class (“Joe, the passenger who is purchasing a ticket from the ticket distributor”).

8. Associations * * Associations denote relationships between classes.
TarifSchedule
TripLeg
Enumeration getZones()
Price getPrice(Zone)
Price Zone * *
Associations denote relationships between classes.
The multiplicity of an association end denotes how many objects the source object can legitimately reference.

9. 1-to-1 and 1-to-many Associations
Country
capital
name:String
name:String
One-to-one association
Point *
Polygon
x: Integer
y: Integer
draw()
One-to-many association

10. Many-to-Many Associations
Lists * *
Company
StockExchange
tickerSymbol *
Lists 1
A stock exchange lists many companies each of them uniquely identifed by a ticker symbol used at that stock exchange.
A company can be listed on more than one stock exchange, using the same ticker symbol.
Mercedes Benz is an example for a company listed on more than one stock exchange: Frankfurt and NYSE.
Does it have two different Ticker symbols?
Something not clear here: What happens if the company cannot have the same ticker symbol on two different stock exchanges?
Company
StockExchange
tickerSymbol
SX_ID
qualifier

11. From Problem Statement To Object Model
oblem Statement: A stock exchange lists many companies. Each
company is uniquely identified by a ticker symbol
Class Diagram:
Company
StockExchange * *
Lists
tickerSymbol

12. From Problem Statement to Code: A
stock exchange lists many companies.
Each company is identified by a ticker Symbol
Class Diagram: * *
StockExchange
Company
Lists
tickerSymbol
Java Code
public class StockExchange {
private Vector m_Company = new Vector(); };
public class Company {
public int m_tickerSymbol;
private Vector m_StockExchange = new Vector(); };

13. Aggregation
An aggregation is a special case of association denoting a “consists of” hierarchy.
The aggregate is the parent class, the components are the children class.
A solid diamond denotes composition, a strong form of aggregation where components cannot exist without the aggregate.
Exhaust system
Muffler
diameter
Tailpipe 1
0..2
Exhaust system 1
0..2
Muffler
Tailpipe
diameter
diameter
TicketMachine 3
ZoneButton

14. Inheritance
Button
ZoneButton
CancelButton
The children classes inherit the attributes and operations of the parent class.
Inheritance simplifies the model by eliminating redundancy.

15. Class Relationships
Our class diagram has the following kinds of relationships.
association -- a relationship between instances of the two classes. There is an association between two classes if an instance of one class must know about the other in order to perform its work. In a diagram, an association is a link connecting two classes.
aggregation -- an association in which one class belongs to a collection. An aggregation has a diamond end pointing to the part containing the whole. In our diagram, Order has a collection of OrderDetails.
generalization -- an inheritance link indicating one class is a superclass of the other. A generalization has a triangle pointing to the superclass. Payment is a superclass of Cash, Check, and Credit.

16. Composition and aggregation
Associations in which an object is part of a whole are aggregations. Composition is a strong association in which the part can belong to only one whole -- the part cannot exist without the whole. Composition is denoted by a filled diamond at the whole end.
This diagram shows that a BoxOffice belongs to exactly one MovieTheater. Destroy the MovieTheater and the BoxOffice goes away! The collection of Movies is not so closely bound to the MovieTheater.

17. Without qualification
Qualifiers
Directory
File
filename
Without qualification 1 *
With qualification
Directory
File
0…1 1
filename
Qualifiers can be used to reduce the multiplicity of an association.

18. Object Modeling in Practice: Class Identification
Foo
Foo, by providing his customerId, can deposit, withdraw, and get balance from his account.
CustomerId
Deposit()
Withdraw()
GetBalance()
Class Identification: Name of Class, Attributes and Methods

19. Object Modeling in Practice: Encourage Brainstorming
“Dada”
CustomerId
Deposit()
Withdraw()
GetBalance()
Foo
CustomerId
Deposit()
Withdraw()
GetBalance()
Account
CustomerId
Deposit()
Withdraw()
GetBalance()
Naming is important!
Is Foo the right name?

20. Object Modeling in Practice ctd
Account
Deposit()
Withdraw()
GetBalance()
Customer
Name
Bank
Name
CustomerId
AccountId
CustomerId
1) Find New Objects
2) Iterate on Names, Attributes and Methods

21. Object Modeling in Practice: A Banking System
Account
Deposit()
Withdraw()
GetBalance()
Customer
Name
CustomerId
AccountId
Bank *
Has
1) Find New Objects
2) Iterate on Names, Attributes and Methods
3) Find Associations between Objects
4) Label the assocations
5) Determine the multiplicity of the assocations

22. Practice Object Modeling: Iterate, Categorize!
Account
Amount
Deposit()
Withdraw()
GetBalance()
CustomerId
AccountId
Bank
Name
Customer
Name * *
Has
CustomerId
Savings
Account
Withdraw()
Checking
Account
Withdraw()
Mortgage
Account
Withdraw()

23. Packages
A package is a UML mechanism for organizing elements into groups (usually not an application domain concept)
Packages are the basic grouping construct with which you may organize UML models to increase their readability.
A complex system can be decomposed into subsystems, where each subsystem is modeled as a package
DispatcherInterface
Notification
IncidentManagement

24. A Class Diagram Example
A customer order from a retail catalog.
Identify the major classes
Customer, Order
How to pay? – Payment
One order can have multiple types of merchandises.
For a merchandise, depending on its quantity, the unit price (or tax) for that order may be different…..
See Practical UML™: A Hands-On Introduction
More complex – Shipping? Stock? Account? Bank?

25. Class Diagram Summary
Class diagrams represent the structure of the system
Name, attribute, operation
Class vs. instance
Association, aggregation, composition, generalization
Multiplicity

26. UML sequence diagrams Used during requirements analysis
selectZone()
pickupChange()
pickUpTicket()
insertCoins()
Passenger
TicketMachine
Used during requirements analysis
To refine use case descriptions
to find additional objects (“participating objects”)
Used during system design
to refine subsystem interfaces
Classes are represented by columns
Messages are represented by arrows
Activations are represented by narrow rectangles
Lifelines are represented by dashed lines

27. Nested messages Dataflow
Passenger
TarifSchedule
Display
ZoneButton
selectZone()
lookupPrice(selection)
price
Dataflow
displayPrice(price)
…to be continued...
The source of an arrow indicates the activation which sent the message
An activation is as long as all nested activations
Horizontal dashed arrows indicate data flow
Vertical dashed lines indicate lifelines

28. …continued from previous slide...
Iteration & condition
Passenger
…continued from previous slide...
CoinIdentifier
Display
CoinDrop
ChangeProcessor *
insertChange(coin)
lookupCoin(coin)
price
Iteration
displayPrice(owedAmount)
Condition
[owedAmount<0] returnChange(-owedAmount)
…to be continued...
Iteration is denoted by a * preceding the message name
Condition is denoted by boolean expression in [ ] before the message name

29. Creation and destruction
Passenger
…continued from previous slide...
ChangeProcessor
Creation
Ticket
createTicket(selection)
print()
Destruction
free()
Creation is denoted by a message arrow pointing to the object.
Destruction is denoted by an X mark at the end of the destruction activation.
In garbage collection environments, destruction can be used to denote the end of the useful life of an object.

30. Sequence Diagram: A Example
Making an online hotel reservation

31. Sequence Diagram Summary
UML sequence diagram represent behavior in terms of interactions.
Useful to find missing objects.
Time consuming to build but worth the investment.
Complement the class diagrams (which represent structure).

32. Represent behavior as states and transitions
State Chart Diagrams
State
Initial state
Event
Transition
Final state
Represent behavior as states and transitions

33. State Chart Diagrams -- Example
A screen savor program

34. Activity Diagrams
An activity diagram shows flow control within a system
An activity diagram is a special case of a state chart diagram in which states are activities (“functions”)
Two types of states:
Action state:
Cannot be decomposed any further
Happens “instantaneously” with respect to the level of abstraction used in the model
Activity state:
Can be decomposed further
The activity is modeled by another activity diagram

35. Statechart Diagram vs. Activity Diagram
Statechart Diagram for Incident (similar to Mealy Automaton)
(State: Attribute or Collection of Attributes of object of type Incident)
Event causes
State transition
Active
Inactive
Closed
Archived
Incident-
Documented
Incident-
Handled
Incident-
Archived
Activity Diagram for Incident (similar to Moore
(State: Operation or Collection of Operations)
Triggerless
Transition
Completion of activity
causes state transition

36. Activity Diagram: Modeling Decisions

37. Activity Diagrams: Modeling Concurrency
Synchronization of multiple activities
Splitting the flow of control into multiple threads
Splitting
Synchronization

38. Activity Diagrams: Swimlanes
Actions may be grouped into swimlanes to denote the object or subsystem that implements the actions.
Dispatcher
Allocate
Resources
Open
Coordinate
Archive
Incident
Resources
Incident
FieldOfficer
Document
Incident

39. What should be done first? Coding or Modeling?
It all depends….
Forward Engineering:
Creation of code from a model
Greenfield projects
Reverse Engineering:
Creation of a model from code
Interface or reengineering projects
Roundtrip Engineering:
Move constantly between forward and reverse engineering
Useful when requirements, technology and schedule are changing frequently

40. UML Summary
UML provides a wide variety of notations for representing many aspects of software development
Powerful, but complex language
Can be misused to generate unreadable models
Can be misunderstood when using too many exotic features
For now we concentrate on a few notations:
Functional model: Use case diagram
Object model: class diagram
Dynamic model: sequence diagrams, statechart and activity diagrams

41. Problems with UML Semi-formal
Go directly to the class/objects – a low level.
Not good at express temporal information – StateChart
Term paper topic for graduate students

42. Additional Slides

43. Models for Plato’s and Aristotle’s Views of Reality
Material reality is a second-class subordinate type of reality.
The first-class type is a “form” Forms lie behind every thing or in the world. Forms can be abstract nouns like “beauty” or “mammal” or concrete nouns like “tree” or “horse”.
There is an important difference between the world of forms and particulars. Forms are nonmaterial, particulars are material. Forms are permanent and changeless. Particulars are changing.
Forms can be acquired intellectually through a “dialectic” process that moves toward the highest understanding of reality through the interaction of questions and answers.
Aristotle accepted the reality of Forms as nonmaterial entities.
However, he could not accept Plato’s idea, that these Forms were not real.
Instead of two separate worlds, one for Forms and one for Particulars, Aristotle had only one world, a world of particular things.
Particular things according to Aristotle have a certain permance about them, even while they are subject to change: A tree changes colors without ceasing to be a tree. A horse grows in size without ceasing to be a horse.
What is the root of this permancence? It is the thing’s internal form, which minds detect, when they penetrate beyond the thing’s changing attributes. So for Aristotle, reality is thus made up of particular things that are each composed of form antdn matter..
lato’s model of reality (UML class diagram).
Reality consists of many particular things and many forms. Note, that forms are not abstract classes that need to be instantiated. Forms such as beauty really exist independent from a particular, that is they can be instantiated by themself.
Aristotle’s model of reality:
Reality consists of many particular things called substances.
Each substance is composed of form and matter.
Beauty is real but it does not exist on its own, it is always part of a really existing thing called the substance.
Using UML, we can illustrate Platon’s and Aristotle’s viewpoints very easily
and see their differences as well

44. Model for Plato’s View of Reality
Material reality is a second-class subordinate type of reality.
The first-class type is a “form” Forms lie behind every thing or in the world. Forms can be abstract nouns like “beauty” or “mammal” or concrete nouns like “tree” or “horse”.
There is an important difference between the world of forms and particulars. Forms are nonmaterial, particulars are material. Forms are permanent and changeless. Particulars are changing.
Forms can be acquired intellectually through a “dialectic” process that moves toward the highest understanding of reality through the interaction of questions and answers.
lato’s model of reality (UML class diagram).
Reality consists of many particular things and many forms. Note, that forms are not abstract classes that need to be instantiated. Forms such as beauty really exist independent from a particular, that is they can be instantiated by themself.
Aristotle’s model of reality:
Reality consists of many particular things called substances.
Each substance is composed of form and matter.
Beauty is real but it does not exist on its own, it is always part of a really existing thing called the substance.

45. Model Aristotle’s Views of Reality
Aristotle accepted the reality of Forms as nonmaterial entities.
However, he could not accept Plato’s idea, that these Forms were not real.
Instead of two separate worlds, one for Forms and one for Particulars, Aristotle had only one world, a world of particular things.
Particular things according to Aristotle have a certain permance about them, even while they are subject to change: A tree changes colors without ceasing to be a tree. A horse grows in size without ceasing to be a horse.
What is the root of this permancence? It is the thing’s internal form, which minds detect, when they penetrate beyond the thing’s changing attributes. So for Aristotle, reality is thus made up of particular things that are each composed of form antdn matter..
lato’s model of reality (UML class diagram).
Reality consists of many particular things and many forms. Note, that forms are not abstract classes that need to be instantiated. Forms such as beauty really exist independent from a particular, that is they can be instantiated by themself.
Aristotle’s model of reality:
Reality consists of many particular things called substances.
Each substance is composed of form and matter.
Beauty is real but it does not exist on its own, it is always part of a really existing thing called the substance.

46. Comparison of Plato’s and Aristotle’s Views
lato’s model of reality (UML class diagram).
Reality consists of many particular things and many forms. Note, that forms are not abstract classes that need to be instantiated. Forms such as beauty really exist independent from a particular, that is they can be instantiated by themself.
Aristotle’s model of reality:
Reality consists of many particular things called substances.
Each substance is composed of form and matter.
Beauty is real but it does not exist on its own, it is always part of a really existing thing called the substance.