Unified Modeling Language (UML)

P.S.Suryateja

Asst. Professor

CSE Department

Vishnu Institute of Technology

The Three Amigos

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Outline

• Introduction to UML
• Importance of modeling
• Principles of modeling
• Object oriented modeling
• Overview of UML
• Conceptual model of the UML
• Architecture
• Software development life cycle (RUP)
• Structural Modeling
• Classes
• Relationships
• Common mechanisms
• Diagrams
• Class diagrams
• Advanced classes
• Advanced relationships
• Object diagrams

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Outline (cont…)

• Behavioral Modeling
• Interactions
• Interaction diagrams
• Use cases
• Use case diagrams
• Activity diagrams
• Events and signals
• State machines
• State chart diagrams
• Architectural Modeling
• Components
• Deployment
• Component diagrams
• Deployment diagrams
• Common modeling techniques

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Prerequisites

• Object orientation concepts

​

• Software engineering

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Objectives

• Learn what is UML.

​

• Learn why UML is relevant to developing software systems.

​

• Learn how to speak the language effectively.

​

• Learn how to apply UML.

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Outcomes

• Ability to read UML models.

​

• Ability to develop UML models.

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Software System - Definition

Software [Set of programs]

(Source Code)

Configuration files, system documentation, end-user documentation, test results, maintenance records etc…

​

+

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Software System - Examples

• Operating systems
• Computer reservation systems
• Air traffic control systems
• Military command and control systems
• Telecommunication networks
• Content management systems
• Database management systems
• Expert systems etc…

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Introduction to Modeling

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Modeling

What?

Where?

Why?

How?

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Model

• A model is a simplified representation of the real thing/system.

​

• A model captures the important aspects of the thing being modeled.

​

• A model is expressed in a medium that is convenient for working.

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Model (cont…)

Construction

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Model (cont…)

Software Design

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Modeling (cont…)

• What?
• The art and science of developing models.

​

• Why?
• To understand the system in a better/easier way.

​

• Where?
• Design phase (most of the time).

​

• How?
• That is what UML is for.

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Importance of Modeling

• We build models to:
• Communicate the structure and behavior of the system.
• Visualize and control the system's architecture.
• Understand the system we are building in a better manner.
• Manage risks.

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Principles of Modeling

1. The choice of what models to create has a profound influence on how a problem is attacked 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 non-trivial system is best approached through a small set of nearly independent models.

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Software Design

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Object Oriented Analysis and Design

• OOAD is a software engineering approach that models a system as a group of interacting objects.

​

• The notation for representing these models is UML.

​

​

• OOA focuses on what the system does. Models consists of use-case, class and interaction diagrams.

​

• OOD focuses on how the system does it. Detailed diagrams.

​

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Object Oriented Modeling

Two approaches for

developing models

Algorithmic

Perspective

Object-Oriented

Perspective

• Traditional approach
• Fundamental unit is function
• Functional decomposition
• Difficult to maintain

• Modern approach
• Fundamental unit is object or class
• Communication through messages
• Easy to maintain and enhance

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What are Models For?

• To capture and precisely state requirements and domain knowledge so that all stakeholders may agree and understand them.

​

• To think about the system design.

​

• To capture design decisions in a mutable form separate from the requirements.

​

• To generate usable work products.

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What are Models For? (cont…)

• To organize, find, filter, retrieve, examine, and edit information about large systems.

​

• To explore multiple solutions economically.

​

• To master complex systems.

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What is in a Model?

• Syntax

​

• Semantics

​

• Presentation

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Modeling work process

Ref: UML 2 Tool Kit by Eriksson, Penker, Lyons, Fado

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Introduction to UML

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UML - Introduction

What?

Where?

Why?

How?

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UML – Introduction (cont…)

• What?
• A modeling language for visualizing, specifying, constructing and documenting the artifacts of a software system.

​

• Why?
• UML is a industry standard modeling language.

​

• Where?
• Design phase (most of the time).

​

• How?
• That is what the subject is about.

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UML Applicable Domains

• Enterprise information systems
• Banking and Financial services
• Telecommunications
• Transportation
• Defense
• Retail
• Medical electronics
• Scientific
• Distributed web-based services

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Why Unified?

• UML is unified across several domains:
• Across historical methods and notations
• Across the development lifecycle
• Across application domains
• Across implementation languages and platforms
• Across development processes
• Across internal concepts

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History of UML

• A major upgrade to UML at the end of 2003:
• Greater consistency
• More precisely defined semantics
• New diagram types
• Backward compatible

Latest Version: 2.4.1

Published on Aug 2011

The Three Amigos

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Overview of UML

• UML
• Visualizing

​

• Specifying

​

• Constructing

​

• Documenting

​

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UML is a Language for Visualizing

• Problems with non-standard modeling (textual):
• Communicating conceptual models to others is error-prone unless everyone involved speaks the same language.

​

• There are some things about a software system you can't understand unless you build models.

​

• If the developer who created the code never wrote down the models that are in his or her head, that information would be lost forever.

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UML is a Language for Specifying

• Specifying means building models that are precise, unambiguous and complete.

​

• UML addresses the specification of all important decisions regarding:
• Analysis
• Design
• Implementation

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UML is a Language for Constructing

• UML models can be directly connected to various programming languages such as Java, C#, VB etc.

​

• Forward engineering

​

• Reverse engineering

​

• Round trip engineering

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Forward Engineering Example

class Customer

{

private int cid;

private String cname;

private String mobile;

private String email;

​

public void purchase( ) { … }

public void login( ) { … }

public void logout( ) { … }

public void search( ) { … }

}

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Reverse Engineering Example

class Customer

{

private int cid;

private String cname;

private String mobile;

private String email;

​

public void purchase( ) { … }

public void login( ) { … }

public void logout( ) { … }

public void search( ) { … }

}

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Roundtrip Engineering Example

class Customer

{

private int cid;

private String cname;

private String mobile;

private String email;

​

public void purchase( ) { … }

public void login( ) { … }

public void logout( ) { … }

public void search( ) { … }

}

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UML is a Language for Documenting

• UML addresses the documentation of a system's architecture and all of its details.

​

• UML provides a language for expressing requirements and for tests.

​

• UML provides a language for modeling the activities of project planning and release management.

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Conceptual Model of UML

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Conceptual Model of UML

• UML building blocks (syntax)
• Rules (semantics)
• Common mechanisms

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UML Building Blocks

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Structural Things

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Behavioral Things

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Grouping Things

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Annotational Things

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Relationships in UML

Dependency

Association

Generalization

Realization

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Diagrams

1. Class diagram
2. Object diagram
3. Use case diagram
4. Sequence diagram
5. Collaboration diagram
6. Statechart diagram
7. Activity diagram
8. Component diagram
9. Deployment diagram

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Rules

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Common Mechanisms

• Specifications
• Adornments
• Common divisions
• Extensibility mechanisms
• Stereotypes
• Tagged values
• Constraints

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Software Architecture

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Architecture

Logical View

Development View

Physical View

Developed by Philippe Kruchten

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Architecture Vs Design

Overall System (Architecture)

Specific Subsystem (Design)

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Unified Process

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Software Development Life Cycle

Rational Unified Process (RUP)

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Unified Process

• The Unified Software Development Process is an industry standard software engineering process
• It is commonly referred to as the "Unified Process" or UP
• It is the generic process for the UML
• It is free - described in "The Unified Software Development Process", ISBN:0201571692"
• UP is:
• Use case (requirements) driven
• Risk driven
• Architecture centric
• Iterative and incremental
• UP is a generic software engineering process. It has to be customised (instantiated) for your project
• In house standards, document templates, tools, databases, lifecycle modifications, …
• Rational Unified Process (RUP) is an instantiation of UP
• RUP is a product marketed and owned by Rational Corporation
• RUP also has to be instantiated for your project

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RUP - Inception

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RUP - Elaboration

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RUP - Construction

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RUP - Transition

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Hello World Example

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Example : Hello World

import java.awt.*;

import java.applet.*;

public class HelloWorld extends Applet

{

public void paint(Graphics g)

{

g.drawString(“Hello World”, 10, 10);

}

}

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Example : Hello World (cont…)

g.drawString(“Hello

World”, 10, 10)

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Example : Hello World (cont…)

Applet

Graphics

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Example : Hello World (cont…)

HelloWorld

Applet

Panel

Container

Component

Object

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Example : Hello World (cont…)

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Structural Modeling

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Structural Modeling

• Structural models represents the structural elements composing a system or function.

​

• These models reflect the static relationships of a structure.

​

• Class diagrams, object diagrams, component diagrams and deployment diagrams.

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Classes

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Classes

• A class is a collection of similar (attributes, operations, relationships) objects.

​

• Classes are used to capture the vocabulary of the system.

​

• Class is represented as a rectangle in UML.

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Classes - Example

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Classes - Name

• A class name is a textual string.

​

• Every class must have a name that distinguishes it from every other class.

​

• A class name may contain any number of letters, numbers and punctuation marks except : which is used to separate a class from its package.

​

• A class name always starts with a uppercase letter.

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Classes – Name (cont…)

Simple names

Path name

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Classes - Attributes

• An attribute is a named property.

​

• These attributes are similar for all the objects of the class.

​

• Graphically the attributes are listed in a compartment below the class name.

​

• The first letter in the attribute name will be in lowercase and the first letter of the rest of the words will be in uppercase.

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Classes – Attributes (cont…)

• Attributes may be represented only with names or along with the type and an initial value.

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Classes - Operations

• An operation is an implementation of service that can be requested from any object of the class to affect its behavior.

​

• These operations are similar for all the objects of the class.

​

• Operations are listed in a compartment below the attributes compartment.

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Classes – Operations (cont…)

• An operation may be represented only with its name or along with the parameters or with the return type.

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Classes - Responsibilities

• A responsibility is the contract of a class that specifies that the objects of that class will have the same attributes and operations.

​

• The attributes and operations are the features by which the class’s responsibilities are carried out.

​

• Graphically responsibilities can be modeled in a separate compartment at the bottom of the class icon.

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Classes – Responsibilities (cont…)

• Responsibilities are represented just as plain text.

​

• A well-structured class will have one or more responsibilities.

​

• Responsibilities can be gathered by using techniques like CRC cards and use case analysis.

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Classes – Responsibilities (cont…)

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Common Modeling Techniques - Modeling the Vocabulary of a System

• To model the vocabulary of a system:

​

• Identify those things that users or implementers use to describe the problem or solution. Use CRC cards and use case-based analysis to help find these abstractions.

​

• For each abstraction, identify a set of responsibilities. Make sure that each class is crisply defined and that there is a good balance of responsibilities among all your classes.

​

• Provide the attributes and operations that are needed to carry out these responsibilities for each class.

​

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Common Modeling Techniques - Modeling the Vocabulary of a System

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Common Modeling Techniques - Modeling the Distribution of Responsibilities in a System

• To model the distribution of responsibilities in a system:�
• Identify a set of classes that work together closely to carry out some behavior.

​

• Identify a set of responsibilities for each of these classes.

​

• Look at this set of classes as a whole, split classes that have too many responsibilities into smaller abstractions, collapse tiny classes that have trivial responsibilities into larger ones, and reallocate responsibilities so that each abstraction reasonably stands on its own.

​

• Consider the ways in which those classes collaborate with one another, and redistribute their responsibilities accordingly so that no class within a collaboration does too much or too little.

​

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Common Modeling Techniques - Modeling the Distribution of Responsibilities in a System

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Common Modeling Techniques - Modeling Non-software Things

• To model non-software things:

​

• Model the thing you are abstracting as a class.

​

•  If you want to distinguish these things from the UML's defined building blocks, create a new building block by using stereotypes to specify these new semantics and to give a distinctive visual cue.

​

• If the thing you are modeling is some kind of hardware that itself contains software, consider modeling it as a kind of node, as well, so that you can further expand on its structure.

​

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Common Modeling Techniques - Modeling Non-software Things

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Common Modeling Techniques - Modeling Primitive Types

• To model primitive types:

​

• Model the thing you are abstracting as a type or an enumeration, which is rendered using class notation with the appropriate stereotype.

​

•  If you need to specify the range of values associated with this type, use constraints.

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Common Modeling Techniques - Modeling Primitive Types

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Relationships

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Relationships

• The classes in the models generally collaborate with each other in a number of ways.

​

• Most of the classes will have connections with other classes known as relationships.

​

• Three main relationships:
• Dependency
• Generalization
• Association

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Relationships - Example

Generalization

Dependency

Association

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Dependency

• A dependency is a using relationship.

​

• Dependency is represented graphically as a dashed directed line.

​

• The dependency is directed towards the thing being used.

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Dependency – Example

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Generalization

• Generalization is often called as “is-a” relationship.

​

• Generalization is a relationship between a general thing and a specific thing.

​

• Generalization specifies that the object of a child can be used at any place where the object of the parent is used.

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Generalization (cont…)

• Generalization is represented as a solid directed line with a large open arrow head pointing towards the general thing.

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Association

• An association is a structural relationship. It specifies that objects of one thing are connected to objects of another thing.

​

• An association can be specified on the same class or between two classes or between more classes.

​

• An association is represented graphically as a solid line connecting two things.

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Association - Name

• An association can have a name. It specifies the type of relationship between the things it is connecting.

​

• We can give a direction to the name by providing a direction triangle that point in the direction you intend to read the name

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Association - Role

• A class plays a specific role in an association relationship.

​

• The role is represented under the association and close to the class icon.

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Association - Multiplicity

• While modeling, it is important to specify how many objects may be connected across an association.

​

• That “how many” is known as the multiplicity of the association.

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Association - Aggregation

• While modeling, sometimes we might want to represent “Whole/Part” relationship. In this relationship, one thing acts as whole, while the other thing is a part of this whole thing.

​

• Such relationship is known as aggregation or also called as “has-a” relationship.

​

• An aggregation is represented graphically by adorning an association with a open diamond at the whole end.

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Association – Aggregation (cont…)

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Common Modeling Techniques - Modeling Simple Dependencies

• To model this using relationship:

​

• Create a dependency pointing from the class with the operation to the class used as a parameter in the operation.

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Common Modeling Techniques - Modeling Single Inheritance

• To model inheritance relationships:

​

• Given a set of classes, look for responsibilities, attributes, and operations that are common to two or more classes.

​

• Elevate these common responsibilities, attributes, and operations to a more general class. If necessary, create a new class to which you can assign these elements (but be careful about introducing too many levels).

​

• Specify that the more-specific classes inherit from the more-general class by placing a generalization relationship that is drawn from each specialized class to its more-general parent.

​

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Common Modeling Techniques - Modeling Single Inheritance

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Common Modeling Techniques - Modeling Structural Relationships

• To model structural relationships:

​

• For each pair of classes, if you need to navigate from objects of one to objects of another, specify an association between the two. This is a data-driven view of associations.

​

• For each pair of classes, if objects of one class need to interact with objects of the other class other than as parameters to an operation, specify an association between the two. This is more of a behavior-driven view of associations.

​

• For each of these associations, specify a multiplicity (especially when the multiplicity is not *, which is the default), as well as role names (especially if it helps to explain the model).

​

• If one of the classes in an association is structurally or organizationally a whole compared with the classes at the other end that look like parts, mark this as an aggregation by adorning the association at the end near the whole.

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Common Modeling Techniques - Modeling Structural Relationships

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Common Mechanisms

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Common Mechanisms

• The extensibility features provided by UML to represent additional information over the basic UML notations are the common mechanisms.

​

• The common mechanisms in UML are:
• Notes
• Adornments
• Stereotypes
• Tagged Values
• Constraints

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Note

• Note is an annotational thing in UML.

​

• Note is used to specify: requirements, observations, reviews, explanations, constraints and other comments.

​

• Note is graphically represented as a rectangle with a dog ear at the top right corner.

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Note - Example

Server

Node

Note

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Adornments

• Adornments are textual or graphical elements that are added to the basic UML notations to specify extra information.

​

Example:

Client

bill.exe

report.exe

contacts.exe

Anonymous

compartment

(Adornment)

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Extensibility Mechanisms

• To represent additional information over the basic notations like class, use case, association etc, UML provides extensibility mechanisms.

​

• Extensibility mechanisms in UML are:
• Stereotypes (extends the building blocks)
• Tagged Values (extends the properties)
• Constraints (extends the semantics)

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Stereotypes

• As we know UML provides basic elements or building blocks. For example, consider a class. A class’s basic notation is a rectangle with three compartments.

​

• Sometimes while creating software blueprints, we might want to represent some elements visually which are not available in UML. For example, in a deployment diagram, I want to represent a router. UML does not provide a notation for a router.

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Stereotypes (cont…)

• So, I must create a new visual representation (icon) for a router. How?

​

• UML already provides a concept known as stereotype using which we can create new building blocks.

​

• Using stereotypes we create new or extend the existing building blocks.

​

• Stereotypes are represented using guillemets (<< >>)

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Stereotypes - Examples

<<interface>>

Movable

<<exception>>

Underflow

<<Router>>

Digicom AX00

Named

stereotype

Named

stereotype with icon

Stereotyped element as icon

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Tagged Values

• Every UML element has its own properties. For example, a class has its own attributes and operations which apply to all its instances.

​

• To represent i.e., extend the properties of an element UML provides tagged values.

​

• Tagged values are represented as text enclosed in braces { }, and placed under the element name.

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Tagged Values - Example

Tagged value

<<library>>

trans.dll

{serverOnly}

Value of tag

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Constraints

• Constraint is mechanism provided by UML to add a new rule or modify the existing rule (semantics) on an element.

​

• Constraints are represented as text enclose in braces { } and placed beside the associated element.

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Constraints - Example

Bank Account

Person

Corporation

owner

owner

{xor}

constraint

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Constraints - Example

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Diagrams

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Diagrams

• Modeling (creating blueprints) is about creating a simplification or abstraction of the end software system.

​

• Modeling involves creating different diagrams.

​

• A diagram is a collection of vertices and edges according to graph theory (mathematics). In UML, these vertices are things and edges are replaced with relationships.

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Diagrams (cont…)

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Diagrams - Overview

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Advanced Classes

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Classifiers

• An modeling element that can have an instance is a classifier.

​

• Examples: classes, usecases, nodes, components etc..

​

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Classifiers (cont…)

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Classifiers - Examples

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Classifiers – Examples (cont…)

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Advanced Classes

• We know that the basic notation of a class in UML is a rectangle with three compartments.

​

• UML also allows to specify more information over this basic notation such as:
• Visibility
• Scope
• Abstract, root, leaf and polymorphic elements
• Multiplicity
• Advanced attributes
• Advanced operations

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Visibility

• The visibility feature of a classifier allows us to specify the accessibility of a certain classifier feature.

​

• Four access specifiers in UML:

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Visibility - Example

- sid

- sname

- rollno

# email

# mobno

+ register( )

+ login( )

+ logout( )

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Scope

• A feature that can be applied to a classifier’s attributes and operations that specifies their existence in all of its instances or existence of only one copy.

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Scope - Example

- sid

- sname

- rollno

# email

# mobno

+ branch : String = CSE

+ register( )

+ login( )

+ logout( )

Classifier scope

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Abstract, Root, Leaf and Polymorphic elements

• An abstract class can be represented in UML with the class name represented in italics.

​

• A class without any parents is a root class. A root class can be represented as a class tagged with {root} property.

​

• A class without child class(s) is a leaf class. A leaf class can be represented as a class tagged with {leaf} property.

​

• Abstract methods or polymorphic methods are also represented in italics similar to abstract classes.

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Abstract, Root, Leaf and Polymorphic elements - Example

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Multiplicity

• The multiplicity feature of a class allows us to specify the number of instances a class can have.

​

• The multiplicity can be applied to the class itself and to attributes also.

​

• The multiplicity of a class is specified at the top right corner of the class symbol.

​

• The multiplicity of an attribute is specified after the attribute name within square brackets.

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Multiplicity - Example

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Attributes

• The syntax of an attribute is as follows:

[visibility] name [multiplicity] [: type] [=initial value] [{property string}]

Some examples:

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Attributes (cont…)

• The three predefined properties that can be used with attributes in UML are:

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Attributes - Example

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Operations

• The syntax of an operation in UML is as follows:

[visibility] name [(parameters-list)] [: return-type] [{property-string}]

Some examples:

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Operations (cont…)

• The syntax of a parameter in the parameters list as follows:

[direction] name :type [=initial value]

Direction may be any one of the following:

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Operations (cont…)

• There are four predefined properties that can be applied to the operations in UML:

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Advanced Relationships

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Advanced Relationships

• We can represent additional information over the basic representation of the relationships:
• Dependency
• Generalization
• Association

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Dependency

• Dependency relationship is also known as the using relationship.

​

• When one thing uses another thing, such relationship is represented using a dependency.

​

• Basic representation of a dependency is as shown below:

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Dependency (cont…)

• Eight stereotypes that can be applied to dependency between classes are:

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Dependency (cont…)

Examples:

​

<<bind>>

<<derive>>

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Dependency (cont…)

<<friend>>

<<instanceOf>>

<<instantiate>>

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Dependency (cont…)

<<powertype>>

<<refine>>

<<use>>

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Dependency (cont…)

• Two stereotypes that can be applied to dependency between packages:

Examples:

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Dependency (cont…)

• Two stereotypes that apply to dependency between use cases:

Examples:

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Dependency (cont…)

• Three stereotypes that apply to dependency among objects:

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Dependency (cont…)

Examples:

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Dependency (cont…)

• One stereotype that applies to dependency in the context of state machines:

• One stereotype that applies to dependency in the context of subsystem:

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Generalization

• Used to represent parent-child or generalization- specialization relationships.

​

• Also known as is-a relationship.

​

• Basic representation of a generalization relationship is a solid line with hollow arrow head.

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Generalization (cont…)

• One stereotype can be applied on generalization:

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Generalization (cont…)

• Four constraints can be applied on generalization relationship:

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Association

• A semantic relationship which specifies a connection between two things is the association.

​

• Basic representation of an association is a solid line.

​

• Over the basic notation, we can represent much more information like:
• Navigation
• Visibility
• Qualification
• Composition
• Association Class

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Association - Navigation

• A directed association specifies the ability to navigate from one thing to another.

​

• Navigability is represented as a stick arrow head.

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Association - Navigation

• Example

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Association - Visibility

• We can specify the visibility of the things that participate in the association relationship.

​

• With the access specifiers on roles we can limit the visibility of a thing from other things outside the association relationship.

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Association - Visibility

• Example

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Association - Qualification

• This feature of an association allows one thing in the association to identify a set of the instances of another thing. Such mechanism is known as qualification.

​

• The attributes set which is used to identify a set of instances is known as a qualifier.

​

• A qualifier is represented as text inside a rectangle which is attached to the corresponding instance.

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Association - Qualification

• Example

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Association – Association Class

• In association relationship, sometimes, the association might have attributes or operations like a class. In such cases, we can model such behavior as an association class.

​

• An association class is represented as a class symbol attached to the association with a dashed line.

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Association – Association Class

• Example

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Association - Composition

• In association relationship, if one thing is a part of another thing, such relationships are known as aggregations.

​

• In a whole-part relationship like aggregation if the life cycle of the part tightly depends on the life cycle of the whole, such relationships are known as compositions.

​

• Compositions are represented as solid lines with solid diamond head.

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Association - Composition

• Example

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Association (cont…)

• Along with the features mentioned before there are six constraints which can be applied on the association:

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Realization

• A semantic relationship in which one thing provides the specification and the other thing provides the implementation for that specification is the realization.

​

• A realization is graphically represented as a dashed line with hollow arrow head which points the thing providing the specification.

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Realization – Examples

HTMLParser

Parser

<<interface>>

scan()

parse()

Htmlparser.dll

Parser

Validate

User

Validation

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CRC (Class-Responsibility-Collaborator) Cards

Introduced by Beck & Cunningham (1989)

Online Shopping System

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Class Diagram

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Class diagram

• Class diagram is used to model the static design view of the system.

​

• A class diagram contains:
• Classes
• Interfaces
• Collaborations
• Generalization, dependencies and associations

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Class diagram – Common Uses

• Class diagrams are commonly used for:
• Modeling the vocabulary of the system
• Modeling the collaborations
• Modeling the logical database schema

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Class diagram - Example

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Object Diagram

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Object diagram

• An object diagram allows us to model the instances of classes in a class diagram.

​

• Object diagrams are used to model the static design view of the system.

​

• An object diagram contains:
• Objects
• Links

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Object diagram – Example

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Class and Object Diagrams

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Behavioral Modeling

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Behavioral Modeling

• Behavioral modeling involves modeling the dynamic aspects of the software system.

​

• The dynamic aspects comprises of the behavior represented as:
• Messages
• States
• Activities and more…

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Use Case Diagram

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Use Cases

• Use cases specify what the system does for its users.

​

• A use case specifies part of the functionality provided by the system.

​

• Use case concept was introduced by Ivar Jacobson

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Use Cases (cont…)

• An use case is defined as “a set of actions performed by the system, which produces an observable result that is, typically, of some value to one or more actors or other stakeholders of the system”.

​

• Use cases are connected to actors through associations.

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Use Cases (cont…)

• Use case is one of the classifiers in UML.

​

• An instance of use case is known as a scenario.

​

• Use case is graphically represented as a hollow ellipse.

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Use Cases – Example

Order product

Validate user

Library :: Make Reservation

Simple Names

Path Name

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Describing Use Cases

• Use case description includes:
• Objective of the use case
• How the use case is initiated
• Flow of messages between actors and the use case
• Alternate flow in the use case
• How the use case finishes and its value to the actor

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Actors

• An actor is one which uses or interacts with the software system (subject).

​

• Actor can be a person or another system (logical or physical).

​

• Use case is always initiated by an actor by sending a message. This message is know as the stimulus.

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Actors (cont…)

• Actors are of two types:
• Active actors
• Passive actors

​

• Actor is graphically represented as a stickman or as a class symbol stereotyped as actor.

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Organizing Use Cases

• We can use packages to group related use cases.

​

• We can use generalization relationship between general and specific use cases.

​

• We can separate common behavior using include dependencies and separate optional behavior using extend dependencies.

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Organizing Use Cases - Packages

College Information System

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Organizing Use Cases - Packages

Use cases in the library package

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Organizing Use Cases - Generalization

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Organizing Use Cases (cont…)

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Use Case Diagrams

• Use case diagrams model the static use case view of a software system.

​

• Specifies what the system does.

​

• Use case diagram contains:
• Use cases
• Actors
• Associations, dependencies and generalizations

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Use Case Diagram – Example

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Use Case Diagram – Example

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Interaction Diagrams

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Interactions

• Interaction is a collection of messages that are exchanged between objects.

​

• A message can be an invocation or operation or a signal.

​

• Using interaction diagrams we can model the flow of control in two ways:
• By focusing on the time ordering of messages.
• By focusing on the structural organization of the objects.

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Interactions - Example

u : User

v : Validator

sendDetails(u,p)

object

object

Link

message

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Interactions (cont…)

• A link is a semantic connection between the objects.

​

• A link is an instance of an association.

​

• Following stereotypes can be applied on links:

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Interactions - Example

Person

+setSalary(s : String)

+assign(d : Department)

Company

employee

employer

1..*

1

p : Person

: Company

assign(development)

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Interactions (cont…)

• A message is the specification of communication among objects that conveys information with the expectation that activity will succeed.

​

• An action takes place when a message is sent.

​

• UML allows us to model following actions:

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Interactions - Example

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Interactions – Sequencing

• In case of nested messages or to explicitly specify the order of the messages we can use sequence numbers.

​

• Prefix the message name with a sequence number followed by a colon ( : ).

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Interactions – Sequencing (cont…)

• There are two types of control flows:
• Procedural flow of control
• Flat flow of control

​

• Procedural flow of control is represented as a solid line with solid arrow head.

​

• Flat flow of control is represented as a solid line with stick arrow head.

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Interactions – Sequencing (cont…)

: View

c : Controller

: Cache

2 : clickAt(p)

2.1 : I = findAt(p)

2.2 : putRecentPick(I)

c : Caller

: Telephone

: Exchange

1 : liftHandset()

2 : assertCall()

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Interaction diagrams

• Interaction diagrams are used to model the interactions among objects.

​

• There are two types of interaction diagrams:
• Sequence diagrams
• Collaboration diagrams

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Sequence Diagrams

• A sequence diagram focuses on the time ordering of messages.

​

• Objects are arranged at the top along the x-axis.

​

• Messages are arranged from top to bottom along the y-axis.

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Sequence Diagrams (cont…)

• Two distinctive features of a sequence diagram:
• Object life line
• Focus of control

​

​

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Sequence Diagrams (cont…)

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Collaboration Diagrams

• A collaboration diagram focuses on the structural organization of the objects in an interaction.

​

• First the objects are plotted and then the objects are connected through links.

​

• Then, the messages are represented.

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Collaboration Diagrams (cont…)

• To denote the order of messages we can use sequence numbers.

​

• Two distinctive features of a collaboration diagram:
• Paths
• Sequence number

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Collaboration Diagrams (cont…)

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Activity Diagrams

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Activity Diagrams

• Activity diagram is used to model the behavior of a system in terms of flow of control between activities.

​

• Activity diagram contains:
• Action and activity states
• Transitions
• Objects

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Activity Diagrams (cont…)

• Action is an atomic computation.

​

• Activity is a non-atomic computation.

​

• Both action and activity states are represented as a rounded rectangle or the lozenge symbol.

Enter User Details

result := getAvg() + 20;

Simple action

expression

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Activity Diagrams (cont…)

• An activity state can have additional details like entry and exit actions.

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Activity Diagrams - Transitions

• A transition is a path from one action or activity state to another which represents the flow of control.

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Activity Diagrams - Branching

• We can represent alternate flows of control using the decision symbol which is graphically represented as a diamond.

​

• A decision symbol can have one incoming transition and two or more outgoing transition.

​

• The flow of control branches based on a boolean expression which is known as a guard condition.

​

• A guard condition is represented in square brackets.

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Activity Diagrams - Branching

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Activity Diagrams – Fork and Join

• Sometimes, we might want to represent parallel or concurrent flow of control.

​

• To represent the transformation of sequential flow of control into concurrent flow, we use a fork.

​

• To represent the transformation of concurrent flow of control into sequential flow, we use a join.

​

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Activity Diagrams – Fork and Join

• To represent a fork and join we use horizontal or vertical synchronization bars.

​

• At a fork, the flow of control above the synchronization bar is sequential and below the bar, the flow is concurrent.

​

• At a join, the flow of control above the synchronization bar is concurrent and below the bar, the flow is sequential.

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Activity Diagrams – Fork and Join

Fork

Join

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Activity Diagrams – Swimlanes

• When a activity diagrams become more and more complex and you want to visually distinguish the activities that belong to a certain object, you can use a swimlane.

​

• A swimlane is a semantic group or collection of all the activities that belong to a particular object.

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Activity Diagrams – Swimlanes

• A swimlane is visually represented as a vertical box.

​

• Transition can move across from one swimlane to another but never does a activity or action state crosses from one swimlane to another.

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Activity Diagrams – Swimlanes

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Events and Signals

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Events and Signals

• In UML, we can model the behavior either through interactions or as a sequence of state changes in a object.

​

• An event is a stimulus which causes an object to move from one state to another.

​

• An event can be any one of the following:
• Signal
• Call
• Passage of time
• Change in state

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Events and Signals (cont…)

• An event can be visually represented as text or using a stereotyped class symbol.

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Events and Signals (cont…)

• There are two types of events:
• Internal events
• External events

​

• External events are the events passed between the system and a user.

​

• Internal events are the events passed within the system.

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Events and Signals (cont…)

• A signal is a named object that is sent asynchronously by one object and then received by another.

​

• Exceptions are the famous examples for signals.

​

• In UML, we can model the signals that an operation can send as a dependency stereotyped with signal.

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Events and Signals (cont…)

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Events and Signals (cont…)

• A call event represents the dispatch of an operation from one object to another.

​

• A call event, in general, is synchronous.

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Events and Signals (cont…)

• A time event represents the passage of time.

​

• In UML, we model the time event using the after keyword followed by an expression that evaluates a period of time.

​

• A change event represents an event that represents a change in state or the satisfaction of some condition.

​

• In UML, change event is modeled using the keyword when followed by some Boolean expression.

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Events and Signals (cont…)

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State Machine

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State Machines

• A state machine is a behavior that represents the sequences of states that an object undergoes during its lifetime in response to events, together with its responses to those events.

​

• The state of an object is a condition or situation during the life of an object during which it satisfies some condition, performs some activity or waits for some event.

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State Machines (cont…)

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State Machines (cont…)

• A state is graphically represented as a rectangle with rounded corners.

​

• A state can be divided into five parts:

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State Machines (cont…)

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State Machines (cont…)

• A transition is a relationship between two states indicating that an object in one state will perform certain actions and enter another state when a specified event occurs and specified conditions are satisfied.

​

• A transition has five parts:

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State Machines (cont…)

• A transition is visually represented as a solid directed line from source state to target state.

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State Machines (cont…)

• UML allows us to represent more advanced information in a state like:
• Entry and exit actions
• Internal transitions
• Activities
• Deferred events

_{Advanced States}

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State Machines – Substates

• A substate is a state included in another state.

​

• In UML, we render a composite state just like a normal state, but with an optional graphic compartment that shows a nested state machine.

​

• Substates may be nested to any level.

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State Machines – Substates (cont…)

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State Machines – Substates (cont…)

• There are situations in which we might want the state machine to remember the last substate that was active prior to leaving the composite state.

​

• A history state allows a composite state that contains sequential substates to remember the last substate that was active in it prior to the transition from the composite state.

​

• In UML, a history is represented as a hollow circle with the symbol ‘H’

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State Machines – Substates (cont…)

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State Machines – Substates (cont…)

• Concurrent substates allow us to specify two or more state machines that execute in parallel in the context of the enclosing object.

​

• Each concurrent substate is divided from each other with a dashed line.

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State Machines – Substates (cont…)

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State Chart Diagrams

• A state chart diagram models the flow of control from one state to another state of an object.

​

• A state chart diagram contains:
• States
• Transitions

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State Chart Diagrams (cont…)

State machine for an ATM

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Architectural Modeling

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Components

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Components

• A component is a physical replaceable part of a system.

​

• Examples of components include:
• Source code files
• Executables
• Libraries
• Tables
• Files
• Documents

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Components (cont…)

• Some more examples:
• ActiveX Control
• Java Bean
• Web Page
• Web Server
• Firewall
• Style Sheet
• Database etc…

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Components (cont…)

• Components are the physical elements that contain the logical elements like classes, interfaces etc…

​

• A component is graphically represented as tabbed rectangle.

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Components (cont…)

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Components (cont…)

• Components Vs Classes:
1. Components are physical things, whereas, classes are logical abstractions.

​

• Components are at a higher level of abstraction than a class.

​

• Components only contain operations, whereas, a class can have both attributes and operations.

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Components (cont…)

• The relationship between a component and its classes can be represented using dependencies.

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Components (cont…)

• An interface contains a set of operations which specify a service to a class or a component.

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• The relationship between a component and an interface can be shown in two ways:
1. Canonical form
2. Iconic form

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Components (cont…)

• There are three kinds of components:
1. Deployment components (Dlls, Exes)
2. Work product components (Source code files)
3. Execution components (COM+ objects)

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Components (cont…)

• UML defines five stereotypes that can be applied to components:

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Components (cont…)

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Component Diagram

• Component diagram is used to model the static implementation view of a system.

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• A component diagram contains:
• Components
• Interfaces
• Dependency, generalization, association and realization relationships

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Component Diagram - Example

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Deployment

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Deployment

• A node is a physical component that exists at runtime.

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• A node generally comprises of some kind of memory and often processing capabilities.

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• Examples of nodes can be:
• PC
• Laptop
• Router
• Other embedded systems

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Deployment (cont…)

• Using nodes we can model the architecture of our software system.

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• A node in UML is graphically represented as a cube.

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Deployment (cont…)

• Nodes and Components:
1. Both have names
2. Both may participate in dependency, generalization and association relationships.
3. Both may be nested
4. Both may have instances
5. Both may participate in interactions

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Deployment (cont…)

• Nodes Vs Components:
1. Components participate in the execution of a software system, whereas, nodes execute components.

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• Component is a physical package of logical elements like classes, whereas, node physically deploys components.

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Deployment (cont…)

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Deployment (cont…)

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Deployment Diagrams

• A deployment diagram is used to model the static deployment view of software system.

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• A deployment diagram contains:
• Nodes
• Dependency and association relationships

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Deployment Diagrams (cont…)

• Common uses:
• To model embedded systems
• To model client/server systems
• To model fully distributed systems

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Deployment Diagrams (cont…)

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Deployment Diagrams (cont…)

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Forward Engineering

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CASE STUDY�Vending Machine

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Vending Machine

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