Modeling - UML

7/23/2019 Modeling - UML

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UML Modeling

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Introduction• UML diagram is designed to let developers and customers view a software

system from a different perspective and in varying degrees of abstraction.

• UML has become a standard modeling language because it is programminglanguage independent.

• Since UML is not a methodology, it does not require any formal work product

Types of UML Diagrams

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Types of UML Diagrams

• Use Case Diagram

Describes the functional behavior of the system as seen by the user.

• Class Diagram

Describes the static structure of the system.

• Sequence Diagram

Describe the dynamic behavior between objects of the system.

Example: Login System

• User browsers the login page and enters theusername & password.

• If the login is successful, the user is redirected to the

main page.

• Otherwise, user has to re-enter the username and

password.

Hint: Consider only about the registered users.

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Use Case Diagram• Consists of:

o Actors

o Use Cases

o The boundary

o The relationships between and among the actors and the use cases.

•An Actor is a model for an external entity whichinteracts with the system.

• User

• External System

• Physical environment (e.g. Weather)

•A Use Case represents a class of functionalityprovided by the system.

•It is a graphical representation of the interactionamong the elements and the system.



Use Case Diagram…

• The main purpose of the use case diagram is to

capture the dynamic aspect of a system.

• The scope of the system can be defined through

use case diagram.

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ActorUse Case

Description of the Use Case

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Class Diagram

• Consists of:o Classes

o and their Relationships

• A class represents a concept.

• A class diagram is a static diagram.

• It describes the static structure of a system.

Class NameAttributes

Operations

Relationship

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Sequence Diagram

• Often built from a use case and a class diagram.

• Sequence diagrams model the dynamic aspects o

a software system.

• Consists of:o Instances of classes/ Objects

o Actors

o Messages



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Extend• Extended use case is meaningful on its own, it is independent of the

extending use case.

• Extending use case typically defines optional behavior that is not

necessarily meaningful by itself.

Example

• Extend relationship is shown as a dashed line with an open

arrowhead directed from the extending use case to the extended

(base) use case. The arrow is labeled with the keyword «extend».

• Registration use case is complete and meaningful on its own.

It could be extended with optional Get Help On Registration use

case.

GetHelpOnRegistrationRegistration

<<extend>>

Include• Use case include is a directed relationship between two use cases which is

used to show that behavior of the included use case (the addition) is insertedinto the behavior of the including (the base) use case.

• The include relationship could be used:

o to simplify large use case by splitting it i nto several use cases,

o to extract common parts of the behaviors of two or more use cases.

• Included use case required, not optional.

• Base use case is incomplete. See below Example

• Checkout use case includes several use cases - Scan Item,Calculate Total and Tax, and Payment

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Calculate Total and Tax

Payment

Checkout

ScanItem<<include>>

<<include>>

<<include>>

Exercise• User browsers the login page and enters the username &

password.

• If the login is successful, the user is redirected to the maipage.

• Otherwise if the user is registered, user has to re-enter thusername and password. If the user is unregistered, userhas to register.

Draw the;

1. Use Case Diagram of the system.

2. Class Diagram of the system.

3. Sequence Diagram for each use case.

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Modeling - UML