basic behavioral modeling chapter 3 of omd

Basic Behavioral Modeling

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A use case diagram help system analyst to discover the requirements of the target system from the users perspective.

Provides functional description of a system & its major processes.

Provides graphic description of the users of a system & what kinds of interactions to exact within that system.

Displays the details of the processes that occur within the application area.

Used to design the test cases for testing the functionality of the system.

Use Case Diagram

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Two types of elementsBusiness rolesBusiness processesActorsUse CaseSystem BoundaryAssociationRelationships in use cases

Elements of a Use Case Diagram

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ActorsAn actor portrays any entity (or entities) that performs

certain roles in a given system. Actor can be users, organization and external system.Actors are responsible for giving input to the system. It is shown as a stick figure in a use case diagram

depicted “outside” the system boundary.Place an actor that initiates a use case on the left of the

use case & an actor receives the results of a use case appears on the right of the use case.


Actor Name

<<actor>>

Iconic Notation for actor member

<<actor>>member

Iconic Notation for actor

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Types of actorsPrimary actors

The main users or entities for which the system is designed, deriving benefits from it directly.

They are completely outside the system & drive the system requirements.

Use the system to achieve an observable user goal.Secondary actors

Users or entities that supervise, operate or manage the system.

They play a supporting role to facilitate the primary actors to achieve their goals.

Often appears to be more inside the system than outside.They are usually allocated many system requirements that

are not drive directly from the statements of requirements.


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Types of actorsPrimary actors

The main users or entities for which the system is designed, deriving benefits from it directly.

They are completely outside the system & drive the system requirements.

Use the system to achieve an observable user goal.Secondary actors

Users or entities that supervise, operate or manage the system.

They play a supporting role to facilitate the primary actors to achieve their goals.

Often appears to be more inside the system than outside.They are usually allocated many system requirements that

are not drive directly from the statements of requirements.


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Use CaseUse case in a use case diagram is a visual

representation of a distinct business functionality in a system.

It is a sequence of transactions performed by the system that produces a major suit for the actor.

A use case is shown as an ellipse in a use case diagram.

It must have unique and textual (simple/qualified) name.


Use Case Request Book

LMS:Request Book

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System BoundaryIt defines the scope of what a system will be.A system cannot have infinite functionality.Defines the limits of the system.It is shown as a rectangle spanning all the use

cases in the system.


Use case

Use case

Use case

Actor

Request book

Issue book

Return book

student

System boundary LM

S

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Communication Lines / RelationshipsUse case diagram has communication lines or

links to show communication between its various components.

AssociationDependency

IncludeExtend

Use case generalization


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AssociationIt is used to describe the relationships between

actors & the use cases they participate in.Association can be unidirectional &

bidirectional.It indicates either that the actor initiates the

use case, or receives the results of executing a use case.

The association is drawn as a solid line.


Use caseUse caseUse case

Actor

Association Request book

Issue book

Return book

student

LMS

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DependencyA relationship between two use cases is

basically a dependency between two use cases.Include

Include is used when two or more use cases share some common portion in the flow of events.

It shows interaction between base use case & inclusion use case .Inclusion use case is consist of feature of base use case.

The stereotype <<include>> identifies the relationship include.


Issue Journal

Issue Book

Verify Library Card

<<include>>

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DependencyExtend

In an extend relationship , the child use case adds to the existing functionality & characteristics of the parent use case

The stereotype <<Extend>> identifies the relationship Extend.


Excess money

Withdraw money

<<Extend>>

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MultiplicityHow many instances of an actor interact with

how many instances of use case.By default we assume one instance of an actor

interacts with one instance of a use case.Multiplicity is indicated by number or with the

range separated by two periods(..) or special character .


Withdraw money

1 0..1

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Use Case GeneralizationA parent-child relationship between use cases.Child use case is the enhancement of the parent

use caseGeneralization is same as extend relationshipIn generalization parent use case can be replaced

by child but it s not possible with extend


Pay bill by post

Pay bill by

internet

Pay Bill

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Use case diagram for online shopping of books

Buy Books

Pay Bill

Prepare Bill

Validate Customer

Search Books

Register Customer

Update Books

<<include>>

<<include>>

<<include>>

<<include>>

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Sequence diagrams describe interaction among classes in terms of an exchange of messages over time.

Depicts the sequence of actions that occurs in a system.

The order of invocation of methods in each object is captured by sequence diagram.

Shows the dynamic behavior of a system.It is two-dimensional in nature.(horizontal axis

shows the life of the object & vertical axis shows the sequence of the creation or invocation of these objects.

Used to model usage scenarios, the logic of methods and the logic of services.

Sequence Diagram

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Class RolesActorLifelinesMessagesActivationCreating objectsDeleting objectsSimple & Block IterationBranching

Elements of Sequence diagram

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Class RolesClass roles describe the way an object will

behave in context. Use the UML object symbol to illustrate class

roles, but don’t list object attributes.

ActorAn external entity that interacts with the system.


Object Name : Class Name :Class Name

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LifelinesVertical dashed lines that indicate the objects

presence over time.


Object : Class

Object : Class

Actor

C : Cashier B : Bill

Customer

Prepare bill <<create>>

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MessagesMessages that arrows that represent communication between

objects.Each message sent to a class invokes a static method/operation on

that class.Each message sent to an object invokes an operation on that object.


Object : Class

Object : Class

Actor


Customer


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Arrow Message Type Description

Synchronous The sender sends message to receiver & wait for the procedure completion receiver.

Simple Messages with single thread of control. One object sends the message to the passive object.

Asynchronous The sender sends the message and immediately continues with the next step.

Return Return message from called procedure of the receiver to the sender.

Delayed message

The message will take significant time to arrive at the receiving object.

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Messages

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ActivationActivation boxes represent the time an object needs to complete a

task.The receiver object is active when it receivers the message from

sender.Each message sent to an object invokes an operation on that object.


Object : Class

Object : Class

Actor


Customer


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Creating objectsObjects can be created during interaction.An object dynamically create a new object by using

<<create>> message.New objects lifeline starts with the receipt of create message.



Customer


<<create>>

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Deleting objectsObjects can be deleted on receiving a <<destroy>> message

from another object.A large Cross (X) is placed at the end of the objects lifeline to

indicate that the objects life has been terminated at that time.


:order

01:OrderLineAdditem(i)

new(i)

:Shopping cart

<<destroy>>

remove(i)

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Structured controlA sequence of messages is fine for showing a single,

linear sequence, but often need to show conditionals & loops.

Shows concurrent execution of multiple sequences.A control operator is shown as a rectangular region

within the sequence diagram.Control operator has a tag a text label inside a small

pentagon in the upper left corner to tell what kind of a control operator it is.

Types of control in sequence diagramOptional ExecutionConditional ExecutionParallel ExecutionLoop(Iterative) Execution


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Simple & block iterationSometimes a task is to be performed repeatedly, then in

sequence diagram such task is represented by a name preceded by an asterisk “ * “.

A repetition or loop within a sequence diagram is depicted as a rectangle.



Customer


B : Bill

Buy product

[all product added]

Get product details

Add product

Update quantity

Calculate total amount

Display total

loop

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Structure controlConditional execution


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break

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Loop/parallel

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optional

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Structure control

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Difference between sequence & collaboration

Sequence Diagram Collaboration Diagram

A sequence diagram is an interaction diagram which emphasizes on the time ordering of messages.

A collaboration Diagram is an interaction diagram which emphasizes the structural organization of the objects that send and receive messages.

Sequence diagrams are alternate representations of an interaction(Collaboration)

Collaboration diagrams are alternate representation of an interaction(sequence)

Sequence diagram describe the interaction among classes in terms of an exchange of message over time.

Collaboration diagram describe the interaction with numbered arrows which shows the movement of messages during the course of a scenario.

Sequence diagram shows the sequence of actions that occurs in system

Collaboration diagram shows the objects and their association with the other objects the system.

The elements of sequence diagram are class roles, activation, Message, lifeline, creating objects, destroying objects and loops.

The elements of Collaboration diagram are objects, Relation / Association, Message.

We can show simple branching in sequence diagram We can show more complex branching in collaboration diagram.

This type of diagram is best used during early analysis phases in design because they are simple and easy to comprehend

This type of diagram is best used for specific scenario.

Sequence diagrams are normally associated with use cases

Collaboration diagram are normally with sequence diagram

Any diagrammatic example explanation of sequence Any diagrammatic example of collaboration diagram

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basic behavioral modeling chapter 3 of omd

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