08 ooad uml-10

Object-Oriented Analysis and Design Using UML
Objectives

In this session, you will learn to:
Identify the concepts of dynamic modeling
Create interaction diagrams

Ver. 1.0 Slide 1 of 21

Introducing Dynamic Modeling Concepts

Dynamic modeling depicts the behavior of the static
constituents of a software system, such as interaction,
workflow, and different states.
You depict the dynamic model of software system using:
• Interaction diagrams: Model the interaction between the
constituents of a software system, such as objects, interfaces,
and abstract classes.
• Activity diagrams: Represent the workflow between the static
constituents.
• State diagrams: Depict the changes that occur in the state of
objects because of the interaction among the various
constituents of a software system.


Difference between Static and Dynamic Modeling

Static modeling is required to represent the physical
structure of a software system.
Dynamic modeling depicts the behavior of the structural
constituents.

Static Modeling Dynamic Modeling

It represents the static or structural It represents the behavior of static constituents
constituents of a software system. of a software system.

It includes class and object diagram. It includes interaction, activity, and state
diagrams.

It helps in depicting the relationships and It helps in expressing and modeling the
dependencies between the constituents of behavior of a system over a period of time.
a system.


Creating Interaction Diagrams

Interaction diagrams:
Depicts how the constituents of a software system interact to
realize use cases of the system.
Can be used to generate executable code through forward and
reverse engineering.
Components of an interaction diagram are:
• Collaboration: Depicts the static aspect of an iteration
diagram.
• Interaction: Depicts the dynamic aspect of an iteration
diagram.


Creating Interaction Diagrams (Contd.)

Collaboration:
Is a collection of instances of classes, relationship among the
instances of classes, and actors.
Groups all those constituents that are required to realize a use
case.
Types of roles in a collaboration are:
• Classifier roles: Describes objects that can form a part of the
collaboration.
• Association roles: Describes links that can form a part of the
collaboration.
Interaction depicts the flow of control in an operation or
among use cases.
In an interaction, an object sends a message to request
another object to perform an operation.



The following table lists the various types of messages that
can be sent from one object to another and their graphical
representation in an interaction diagram.

Message Description Graphical Representation

Call Specifies the invocation of a
method of an object.

Return Specifies the invocation of a
method of an object.
Send Sends an asynchronous
signal to an object.

Create Creates an object.

Destroy Destroys an object.



The commonly used interaction diagrams are:
Sequence diagrams
Communication diagrams


Creating Sequence Diagrams

Sequence diagram:
Represents an interaction among objects in the form of
messages ordered in a sequence by time.
The following figure depicts the arrangement of objects and
messages in a sequence diagrams.


Creating Sequence Diagrams (Contd.)

Guidelines for modeling sequence diagrams are:
Identify the collaboration for interaction in system, subsystem,
and use cases.
Identify the objects that have higher responsibility in the
interaction. Place the objects with high responsibility on one
side and the low responsibility objects on the other.
Identify the lifeline of each object in view of control to depict the
creation and destruction of an object.
Identify the messages that flow between the lifeline of objects.
Identify pre-conditions and post-conditions for each message
to control the flow of objects.


Creating Communication Diagrams

Communication Diagram:
Represent the interaction among objects in the form of
messages.
The following figure shows a communication diagram.


Creating Communication Diagrams (Contd.)

Guidelines for modeling a communication diagrams are:
Identify the collaboration that involves interaction in the
system, subsystem, and use cases.
Identify the objects that have higher responsibility in the
interaction. Draw these objects on a graph so that the objects
with high responsibility are placed on one side and the objects
with lower responsibility are placed on the other.
Identify the links between objects. You need to place the
association links for depicting the relationship among objects.
Identify all the messages that flow across the links established
among objects.


Assigning Responsibilities to Classes

Assigning responsibilities to a class or a set of classes
ensures that the software system has the desired
functionality as per the requirement document.
Decisions about responsibilities of classes are taken during
the creation of interaction diagrams.
A responsibility is implemented using methods of classes,
which may implement the entire responsibility or collaborate
with other methods.


Assigning Responsibilities to Classes (Contd.)

Guidelines for assigning responsibilities to objects are:
Assign responsibilities to classes such that they perform all
tasks that are performed by the real world entity it represents.
Assign responsibilities to a class if the class has the attributes
that will enable it to fulfill the responsibilities.
Assign responsibilities to multiple classes if all classes have
data to fulfill the responsibility.
Distribute responsibilities evenly to the various classes of your
software system.
Check that all classes of the software system have some
responsibility assigned to them. If no responsibility is assigned
to a class, you need to check if the class is required.


Assigning Responsibilities to Classes (Contd.)

Check if too many or unrelated responsibilities have been
assigned to a class. If such a class exists, split the class into
smaller classes.


Just a minute

Which of the following diagrams represents the interaction
among objects in the form of messages?
1. Composite structure diagrams
2. Communication diagrams
3. Timing diagrams
4. Interaction Overview diagrams

Answer:
Communication diagrams


Demo: Modeling the Dynamic View of the Bank ATM System

Problem Statement:
Janes Technology has been assigned the task of creating a
dynamic model of the prototype for the InfoSuper bank ATM
system. Janes Technology needs to implement only the cash
withdrawal system in the prototype for the InfoSuper bank. The
following table describes classes, attributes, and operations for
the cash withdrawal feature of the InfoSuper bank, which the
design team of Janes Technology has identified.

Class Operations Desciption
ATM Show() Displays the location and branch name of the ATM.

ATMCard GetPin() Accepts the PIN entered by the customer and
verifies it.
GetAccount() Fetches the account information based on the
card_ID and PIN.

SetPin(int)
Updates the PIN.


Demo: Modeling the Dynamic View of the Bank ATM System (Contd.)

BankCustomer InsertCard() Prompts the customer to insert ATM
card.

SelectTransaction() Select a transaction from a list of
transactions.
EnterPin()
Prompts the customer to enter PIN.

ChangePin() Invokes the PIN change request. Enters
the new PIN.
Invokes the cash withdrawal operation.
WithdrawCash()

RequestTransactionSummary() Requests for a transaction summary.
Account CalculateInterest() Calculates the interest for the account.
This is an abstract operation.

UpdateAccount() Updates the account information.

VerifiyWithdrawalAmount() Verifies if the amount to be withdrawn is
less than the account balance amount.



CurrentAccount CalculateInterest() Calculates the interest for the current
account.
SavingsAccount CalculateInterest() Calculates the interest for the savings
account
Transaction getAccountBalance() Gets the balance of the account.

StartTransaction() Initiates the transaction.

CancelTransaction Cancels the transaction.
CardScanner AcceptCard() Accept/rejects the ATM card.

ReadCard() Reads the Card_Id associated with the
ATM card.

EjectCard() Ejects the ATM card.



DisplayScreen Prompt() Prompts the respective screen as per request.

AcceptInput() Accepts the required input on the displayed
screen.

CashDispenser SupplyCash() Supplies the verified amount as cash.

GenerateRecipt() Generates a receipt for the cash dispensed.

The design team also created the following class diagram after
identifying the classes and operations for InfoSuper bank.

Class Diagram



Solution:
To model the dynamic view of the cash withdrawal feature of
the ATM system, you need to perform the following tasks:
Identify the collaboration and interactions.
Create a sequence diagram.
Create a communication diagram.


Summary

In this session, you learned that:
Dynamic modeling is used to understand the interaction among
objects and the states of objects of software systems.
Interaction diagrams show an interaction between the objects
of a collaboration. Few interaction diagrams are: sequence and
communication.
Sequence diagram is a type of interaction diagrams that is
used to model the flow of control by time ordering.
Communication diagrams represent the interaction among
objects in the form of messages.


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