Object-Oriented Modeling Using Modified Modeling Language (UML)

Object-Oriented Modeling Using

Modified Modeling Language

(UML)

CS 3300 Object-Oriented Concepts Object-Oriented Modeling Using UML 2

Outline

• Unified Modeling Language• Principles and Concepts• Modeling Relations and Structures• Modeling Dynamic Behavior• Modeling Requirements with Use

Cases


What is a Model?

A model is a simplification of reality.A model may provide

– blueprints of a system– Organization of the system– Dynamic of the system


Why We Model

“A successful software organization is one that consistently deploys quality software that meets the needs of its users. An organization that can develop such software in a timely and predictable fashion, with an efficient and effective use of resources, both human and material, is one that has sustainable business.”


Why We Model

• Model is built to– Communicate the desired structure and

behavior of the system– Visualize and control the system’s

architecture– Better understand the system that being

built– Manage risk– Expose opportunities for simplification and

reuse


Why We Model

• We build models so that we can see and better understand the system we are developing.


Importance of Modeling

• Models help us– to visualize a system as it is or as we

want it to be.– to specify the structure or behavior of

a system.– in providing a template that guides us

in constructing a system.– in providing documenting the

decisions we have made.


Principles of Modeling

• The choice of what models to create has a major influence on how a problem is approached and how a solution is shaped.

• Every model may be expressed at different levels of precision.

• The best models are connected to reality.• No single model is sufficient. Every

nontrivial system is best approached through a small set of nearly independent models.


Objected-Oriented Modeling

• Two most common ways in modeling software systems are– Algorithmic

• Procedures or functions

– Object oriented• Objects or classes


What is UML?

• UML is a language for– Visualizing– Specifying– Constructing– Documenting


Building Blocks of UML

• Things -- abstraction • Relations -- tie things together• Diagrams -- group interesting

collections of things


Principles and Concepts

• Objects and Classes• Principles


Objects and Classes

Interpretation in the Real World

Interpretation in the Model

Object

An object is a thing that can be distinctly identified.

An object has an identity, a state, and a behavior.

Class

A class represents a set of objects with similar characteristics and behavior. This objects are called the instances of the class.

A class characterizes the structure of states and behaviors that are shared by all instances.


Objects

• Each of object has a unique identity.• The state of an object is composed of a set of

fields (data fields), or attributes.• Each field has a name, a type, and a value.• Behaviors are defined by methods.• Each method has a name, a type, and a value.• Each method may or may not return a value.• Features are a combination of the state and

the behavior of the object.


Properties of Objects

• Two objects are equal if their states are equal.

• Two objects are identical if they are the same objects.

• The values of the fields are mutable.• Methods that do not modify the state of

the object are called accessors.• Methods that modify the state of the

object are called mutators.• Objects can be mutable or immutable.


Classes

• A class defines a template for creating or instantiating its instances or objects.

• A class is a description of a set of objects that share the same attributes, operations, relationships, and semantics.


Classes• A class defines --

– the names and types of all fields– the names, types, implementations of all methods

• The values of the fields are not defined or fixed in the class definition.

• The values of the fields are mutable.• Each instance of the class has its own state.• Different instances of the class may have different

states.• The implementations of methods are defined in the

class definition and fixed for a given object.• Values of methods are immutable


Example

Class name: Point class Point {Fields: x, y int x, y;Method: move public void move (int dx, int dy){

// implementation

}


UML Notation for Classes

ClassNameThe top compartment shows the class name.

field1

…fieldn

The middle compartment contains the declarations of the fields of the class.

method1

…methodm

The bottom compartment contains the declarations of the methods


Field Declaration

• The name of the field is required in the field declaration.

• Field declaration may include:[Visibility][Type]Name[[Multiplicity]][=InitialValue] [Visibility]Name[[Multiplicity]][:Type][=InitialValue]

• Visibility or accessibility defines the scope:– Public -- the feature is accessible to any class– Protected -- the feature is accessible to the class

itself, all the classes in the same package, and all its subclasses.

– Package -- the feature is accessible to the class itself and all classes in the same package.

– Private -- the feature is only accessible within the class itself.


Visibility syntax in Java and UML

Visibilty Java Syntax UML Syntax

public public +

protected protected #

package ~

private private -


Examples

Java Syntax UML Syntax

Date birthday Birthday:Date

Public int duration = 100 +duration:int = 100

Private Student students[0..MAX_Size]

-students[0..MAX_Size]:Student


Method Declaration

• The name of the method is required in the method declaration.

• Method declaration may include:[Visibility][Type]Name([Parameter, ...])

[Visibility]Name([Parameter, ...])[:Type]

• Each parameter of a method can be specified by -- Type Name


Examples

Java Syntax UML Syntax

void move(int dx, int dy) ~move(int dx, int dy)

public int getSize() +int getSize()


Example

Point

private int x

private int y

public void move(int dx,int dy)

Point

-x:int

-y:int

+move(dx:int,dy:int)

Point

x

y

move()


UML Notation for Object

ObjectName : ClassName

The top compartment shows the object name and its class.

field1 = value1

…fieldn = valuen

The bottom compartment contains a list of the fields and their values.

objectName -- objectName whose class is of no interest

:ClassName -- anonymous object of ClassName which can be

identify only through its relationship with other object.


Examples

P1:Point Point p1 = new Point();

x = 0

y = 0

p1.x = 0;

P1.y = 0;

P1:Point Point p1 = new Point();

x = 24

y = 40

p1.x = 24;

P1.y = 40;


Message Passing orMethod Invocation

• Objects communicate with one another through message passing.

• A message represent a command sent to an object -- recipient

• A message consists of the receiving object, the method to be invoked and the arguments to method.


Example

p1.move(10,20)

Recipient p1

Method move()

Arguments (10,20)


Packages

• Package name are in lower case --Java.awt.event

javax.swing.*

• Packages that will be widely used should be named as the reverse of the internet domain as the prefix of the package name --EDU.emporia.mathbeans.MathTable

EDU.emporia.mathtools.*


UML notation of packages


Principles

• Modularity: – alleviate complexity of large-scale systems

• Abstraction:– separating the essential from the non-essential

characteristics of an entity

• Encapsulation:– Information hiding

• Polymorphism:– Portability

• Levels of Abstraction:– Organization of classes and interfaces


Principle of Modularity

• A complex software system should be decomposed into a set of highly cohesive but loosely coupled modules.

• The basic for decomposition are cohesion and coupling.– Cohesion -- functional relatedness of the entities within

modules.– Coupling – inter-dependency among different modules.

• Each module is relatively small and simple• Interactions among modules are relatively simple• hierarchical


Principle of Abstraction

• The behaviors or functionalities should be precisely characterized as contractual interface which captures the essence of the behavior.

• The complexity of the module is hidden from the clients.


Principle of Encapsulation

• The implementation of a module should be separated from its contractual interface and hidden from the clients of the module.

• Information hiding


Principle of Polymorphism

• Ability to interchange modules dynamically without affecting the system.

• refers to a contractual interface with multiple interchangeable implementation


Modeling Relationships and Structures

• A class diagram consists of– A set of nodes that represent classes and

interfaces– A set of links represent relationships among

classes

• Class diagrams can be used to model:– Inheritance -- extension and implementation– Association -- aggregation and compostion– Dependency


Inheritance• Define a relationship among

classes and interfaces• Inheritance model -- the is-a(n)

relationship


Example


Principle of Levels of Abstraction

• Abstractions can be organized into different levels.

• Higher level is more general


Association

• Association represents binary relationship between classes

Student Course

Faculty

advisee

adviser

* enroll

teach

* *

1 1

*


Aggregation and Compositon

• Aggregation is a special form of association– Has-a or part-whole relationship

• Composition is a stronger form of aggregation


Example

University Department

Faculty

Chairman-of Member-of

* *College Student*11 1

11

1 1..*


Dependency• Dependency is a relationship

between entities such that the proper operation of one entity depends on the presence of the other entity, and changes in one entity would affect the other entity.


Example

Registrar

void addCourse(CourseSchedule a, Course c)

void removeCourse(CourseSchedule Course findCourse(String title)

void enroll(Course c, Student s)void drop(Course c, Student s

CourseSchedule

Course

Student


Modeling Dynamic Behavior

• Sequence diagram– Depict object interaction by

highlighting the time ordering of method invocation


Example



• State diagram– Depict the flow of control using the

concepts of state and transitions– Labels of transitions are in the form:

[Event-List][[Guard]][/Action]- Entry action and exit action

entry/Action1

exit/Action2


Graphical notations



• Nested state diagram– Composite of state diagrams


Example

talk


Modeling Requirements with Use Cases

• Use cases describes the externally observable behavior of system functions in the form of interactions between the system to be developed and the external entities -- Actors.

• Actors may represent roles played by users of the system or other systems.

• Consist of a name and scenarios• One of scenarios is the main scenario


Use Case Diagram• Consist of:

– Use cases– Actors– Relationships among actors and use

cases


Extension relationships among actors


Dependency relationships among use cases


Case Study: An E-Bookstore

• Problem requirements• Program specifications• Object models

– Identifying classes– Identifying the features of classes --

states and behaviors– Identifying relationships among

classes – inheritance and interfaces.


Requirements

• Allow customers to browse and order books, music CDs, and computer software


Specifications

• Provide information on the books, CDs, and software

• Provide a functionality for customers registration as well as updating customer’s information

• Provide a functionality for ordering and shipping

• Provide a functionality for updating inventory


Register

Shop

ManageAcount

Process order

Manage catalog

Logon

Customer

System administrator

Inventory manager

Manager

Catalog Manager

Object-Oriented Modeling Using Modified Modeling Language (UML)

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