�Modeling with UML

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 1

Overview: modeling with UML

• What is modeling?
• What is UML?
• Use case diagrams
• Class diagrams

​

Next lecture

• Sequence diagrams
• Activity diagrams

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 2

What is modeling?

• Modeling consists of building an abstraction of reality.
• Abstractions are simplifications because:
• They ignore irrelevant details and
• They only represent the relevant details.
• What is relevant or irrelevant depends on the purpose of the model.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 3

Example: street map

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 4

Why model CPS?

Why model CPS?

​

• CPSis getting increasingly more complex
• heterogeneous with huge cluster of devices
• A single programmer cannot manage this amount of code in its entirety.
• Code is not easily understandable by developers who did not write it
• We need simpler representations for complex systems
• Modeling is a mean for dealing with complexity

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 5

Systems, Models and Views

• A model is an abstraction describing a subset of a system
• A view depicts selected aspects of a model
• A notation is a set of graphical or textual rules for depicting views
• Views and models of a single system may overlap each other

​

Examples:

• System: Aircraft
• Models: Flight simulator, scale model
• Views: All blueprints, electrical wiring, fuel system

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 6

Systems, Models and Views

Aircraft

​

Flightsimulator

​

Scale Model

​

Blueprints

Electrical

Wiring

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 7

Models, Views and Systems (UML)

System

Model

View

*

*

Depicted by

Described by

Airplane: System

Blueprints: View

Fuel System: View

Electrical Wiring: View

Scale Model: Model

Flight Simulator: Model

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 8

Concepts and Phenomena

Phenomenon

• An object in the world of a domain as you perceive it
• Example: The lecture you are attending
• Example: My black watch

Concept

• Describes the properties of phenomena that are common.
• Example: Lectures on software engineering
• Example: Black watches

Concept is a 3-tuple:

• Name (To distinguish it from other concepts)
• Purpose (Properties that determine if a phenomenon is a member of a concept)
• Members (The set of phenomena which are part of the concept)

​

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 9

Concepts and phenomena

• Abstraction
• Classification of phenomena into concepts
• Modeling
• Development of abstractions to answer specific questions about a set of phenomena while ignoring irrelevant details.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 10

Concepts in software: Type and Instance

• Type:
• An abstraction in the context of programming languages
• Name: int, Purpose: integral number, Members: 0, -1, 1, 2, -2, . . .
• Instance:
• Member of a specific type
• The type of a variable represents all possible instances the variable can take

​

The following relationships are similar:

• “type” <–> “instance”
• “concept” <–> “phenomenon”

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 11

Abstract Data Types & Classes

• Abstract data type
• Special type whose implementation is hidden from the rest of the system.
• Class:
• An abstraction in the context of object-oriented languages
• Like an abstract data type, a class encapsulates both state (variables) and behavior (methods)
• Class Vector
• Unlike abstract data types, classes can be defined in terms of other classes using inheritance

​

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 12

Application and Solution Domain

• Application Domain (Requirements Analysis):
• The environment in which the system is operating

​

• Solution Domain (System Design, Object Design):
• The available technologies to build the system

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 13

Object-oriented modeling

Application Domain

Solution Domain

Application Domain Model

System Model

Aircraft

TrafficController

FlightPlan

Airport

MapDisplay

FlightPlanDatabase

SummaryDisplay

TrafficControl

TrafficControl

UML Package

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 14

What is UML?

• UML (Unified Modeling Language)
• An emerging standard for modeling object-oriented software.
• Resulted from the convergence of notations from three leading object-oriented methods:
• OMT (James Rumbaugh)
• OOSE (Ivar Jacobson)
• Booch (Grady Booch)
• Reference: “The Unified Modeling Language User Guide”, Addison Wesley, 1999.
• Supported by several CASE tools
• Rational ROSE
• TogetherJ

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 15

UML: First Pass

• You can model 80% of most problems by using about 20 % UML
• We teach you those 20%

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 16

UML First Pass

• Use case Diagrams
• Describe the functional behavior of the system as seen by the user.
• Class diagrams
• Describe the static structure of the system: Objects, Attributes, Associations
• Sequence diagrams
• Describe the dynamic behavior between actors and the system and between objects of the system
• Statechart diagrams
• Describe the dynamic behavior of an individual object (essentially a finite state automaton)
• Activity Diagrams
• Model the dynamic behavior of a system, in particular the workflow (essentially a flowchart)

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 17

UML first pass: Use case diagrams

Actor

Use case

Package

Use case diagrams represent the functionality of the system

from user’s point of view

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 18

UML first pass: Class diagrams

1

2

push()�release()

Watch

Class

Association

Multiplicity

Attribute

Operations

Class diagrams represent the structure of the system

state

PushButton

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 19

UML first pass: Sequence diagram

Object

Message

Activation

Sequence diagrams represent the behavior as interactions

Actor

Lifeline

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 20

UML first pass: Statechart diagrams for objects with interesting dynamic behavior

State

Initial state

Final state

Transition

Event

Represent behavior as states and transitions

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 21

Other UML Notations

UML provide other notations that we will be introduced in subsequent lectures, as needed.

​

• Implementation diagrams
• Component diagrams
• Deployment diagrams
• Introduced in lecture on System Design
• Object constraint language
• Introduced in lecture on Object Design

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 22

UML Core Conventions

• Rectangles are classes or instances
• Ovals are functions or use cases
• Instances are denoted with an underlined names
• myWatch:SimpleWatch
• Joe:Firefighter
• Types are denoted with non underlined names
• SimpleWatch
• Firefighter
• Diagrams are graphs
• Nodes are entities
• Arcs are relationships between entities

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 23

Use Case Diagrams

• Used during requirements elicitation to represent external behavior

​

• Actors represent roles, that is, a type of user of the system
• Use cases represent a sequence of interaction for a type of functionality
• The use case model is the set of all use cases. It is a complete description of the functionality of the system and its environment

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 24

Actors

• An actor models an external entity which communicates with the system:
• User
• External system
• Physical environment
• An actor has a unique name and an optional description.
• Examples:
• Passenger: A person in the train
• GPS satellite: Provides the system with GPS coordinates

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 25

Use Case

A use case represents a class of functionality provided by the system as an event flow.

​

A use case consists of:

• Unique name
• Participating actors
• Entry conditions
• Flow of events
• Exit conditions
• Special requirements

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 26

Use Case Diagram: Example

Name: Purchase ticket

​

Participating actor: Passenger

​

Entry condition:

• Passenger standing in front of ticket distributor.
• Passenger has sufficient money to purchase ticket.

​

Exit condition:

• Passenger has ticket.

Event flow:

1. Passenger selects the number of zones to be traveled.

2. Distributor displays the amount due.

3. Passenger inserts money, of at least the amount due.

4. Distributor returns change.

5. Distributor issues ticket.

​

​

Anything missing?

Exceptional cases!

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 27

The <<extends>> Relationship

• <<extends>> relationships represent exceptional or seldom invoked cases.
• The exceptional event flows are factored out of the main event flow for clarity.
• Use cases representing exceptional flows can extend more than one use case.
• The direction of a <<extends>> relationship is to the extended use case

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 28

The <<includes>> Relationship

• <<includes>> relationship represents behavior that is factored out of the use case.
• <<includes>> behavior is factored out for reuse, not because it is an exception.
• The direction of a <<includes>> relationship is to the using use case (unlike <<extends>> relationships).

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 29

Use Case Diagrams: Summary

• Use case diagrams represent external behavior
• Use case diagrams are useful as an index into the use cases
• Use case descriptions provide meat of model, not the use case diagrams.
• All use cases need to be described for the model to be useful.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 30

Class Diagrams

• 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.

​

​

Enumeration getZones()

Price getPrice(Zone)

*

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 31

Classes

• 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.

Name

Attributes

Operations

Signature

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 32

Instances

• 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.

​

zone2price = {

{‘1’, .20},�{‘2’, .40},

{‘3’, .60}}

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 33

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”).

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 34

Associations

• Associations denote relationships between classes.
• The multiplicity of an association end denotes how many objects the source object can legitimately reference.

Price�Zone

​

​

Enumeration getZones()

Price getPrice(Zone)

*

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 35

1-to-1 and 1-to-many Associations

Country

name:String

City

name:String

Has-capital

Polygon

draw()

Point

x: Integer

y: Integer

One-to-one association

One-to-many association

*

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 36

Many-to-Many Associations

StockExchange

Company

tickerSymbol

Lists

*

*

StockExchange

Company

Lists

1

*

tickerSymbol

SX_ID

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 37

From Problem Statement To Object Model

Pr

oblem Statement: A stock exchange lists many companies. Each

company is uniquely identified by a ticker symbol

Class Diagram:

StockExchange

Company

tickerSymbol

Lists

*

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 38

From Problem Statement to Code

public class StockExchange

{

private Vector m_Company = new Vector();

};

public class Company

{

public int m_tickerSymbol;

private Vector m_StockExchange = new Vector();

};

Pr

oblem Statement

:

A

stock exchange lists many companies.

Each company is identified by a ticker Symbol

Class Diagram:

Java Code

StockExchange

Company

tickerSymbol

Lists

*

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 39

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. (Bill of Material)

​

3

Exhaust system

Muffler

diameter

Tailpipe

diameter

1

0..2

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 40

Qualifiers

• Qualifiers can be used to reduce the multiplicity of an association.

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 41

Inheritance

• The children classes inherit the attributes and operations of the parent class.
• Inheritance simplifies the model by eliminating redundancy.

​

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 42

Object Modeling in Practice: Class Identification

Foo

Betrag

CustomerId

Deposit()

Withdraw()

GetBalance()

Class Identification: Name of Class, Attributes and Methods

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 43

Object Modeling in Practice: �Encourage Brainstorming

Naming is important!

Is Foo the right name?

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 44

Object Modeling in Practice ctd

CustomerId

1) Find New Objects

CustomerId

​

2) Iterate on Names, Attributes and Methods

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 45

Object Modeling in Practice: A Banking System

1) Find New Objects

2) Iterate on Names, Attributes and Methods

3) Find Associations between Objects

Has

4) Label the assocations

5) Determine the multiplicity of the assocations

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 46

Practice Object Modeling: Iterate, Categorize!

CustomerId()

Has

*

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 47

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

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 48

UML sequence diagrams

• 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

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 49

Nested messages

• 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

ZoneButton

Dataflow

…to be continued...

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 50

Iteration & condition

• Iteration is denoted by a * preceding the message name
• Condition is denoted by boolean expression in [ ] before the message name

ChangeProcessor

Iteration

Condition

​

…to be continued...

…continued from previous slide...

*

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 51

Creation and destruction

• 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.

ChangeProcessor

…continued from previous slide...

Creation

Destruction

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 52

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).

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 53

State Chart Diagrams

State

Initial state

Final state

Transition

Event

Represent behavior as states and transitions

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 54

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

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 55

Statechart Diagram vs. Activity Diagram

Active

Inactive

Closed

Archived

Incident-

Handled

Incident-

Documented

Incident-

Archived

Statechart Diagram for Incident (similar to Mealy Automaton)

(State: Attribute or Collection of Attributes of object of type Incident)

Activity Diagram for Incident (similar to Moore

(State: Operation or Collection of Operations)

Triggerless

Transition

Completion of activity

causes state transition

Event causes

State transition

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 56

Activity Diagram: Modeling Decisions

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 57

Activity Diagrams: Modeling Concurrency

• Synchronization of multiple activities
• Splitting the flow of control into multiple threads

Synchronization

Splitting

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 58

Activity Diagrams: Swimlanes

• Actions may be grouped into swimlanes to denote the object or subsystem that implements the actions.

​

Open

Incident

Allocate

Resources

Coordinate

Resources

Document

Incident

Archive

Incident

Dispatcher

FieldOfficer

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 59

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

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 60

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

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 61

Additional Slides

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 62

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.

Plato

• 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..

Aristotle

Using UML, we can illustrate Platon’s and Aristotle’s viewpoints very easily

and see their differences as well

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 63

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.

Plato

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 64

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..

Aristotle

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 65

Comparison of Plato’s and Aristotle’s Views

Plato

Aristotle

Bernd Bruegge & Allen H. Dutoit Object-Oriented Software Engineering: Using UML, Patterns, and Java 66