UML Class and Use Case Diagrams

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Unified Modeling Language
Rajthilak S

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Many Stakeholders , many views
 Architecture may be many things to many different stakeholders
 End user
 Project Manager
 System Engineer
 Developer
 Tester
 Maintainer
 Multidimensional Reality
 Many Stakeholders
multiple views , multiple blueprints

Models
 Modeling is the designing of software applications before coding.
 Models are the higher level of abstraction of the System.
 A model plays the analogous role in software development that blueprints and
other plans (site maps, elevations, physical models) play in the building of a
skyscraper.
 Modeling is the only way to visualize the design and check it against
requirements before one starts to code.
 Models are also the vehicle for communication with various stake holders.

What is UML?
 General-purpose modeling language
 Helps to specify, visualize, and document models of software systems
 High Level abstraction of the system
 Represents the system using Graphical Notations from various Perspectives
 used for business modeling and modeling of other non-software systems too
 UML 2.0

Evolution of UML
 Successor to the wave of Object Oriented Analysis and
Design(OOA&D).
 unifies the notations used by three amigos(Grady Booch, Ivar
Jacobson and James Rumbaugh) in their OO methods.
 OMG

Different Perspectives of System

Basic OO Terms
 A model is an abstraction of the underlying problem.
 The domain is the actual world from which the problem comes.
 Models consist of objects that interact by sending each other messages.
 Objects have things they know (attributes) and things they can do (behaviors
or operations).
 The values of an object's attributes determine its state.
 Classes are the "blueprints" for objects. A class wraps attributes (data) and
behaviors (methods or functions) into a single distinct entity. Objects are
instances of classes.

The Unified Modelling Language – 1.4
Structural Diagrams- class,object,component,deployment diagrams.
Behavioural Diagrams – Use Case , Activity and State Chart diagrams.
Interaction Diagrams – Sequence and Collaboration diagrams.
Use Case
Diagrams
Use Case
Diagrams
Use Case
Diagrams
Scenario
Diagrams
Scenario
Diagrams
Collaboration
Diagrams
State
Diagrams
State
Diagrams
Component
Diagrams
Component
Diagrams
Component
Diagrams
Deployment
Diagrams
State
Diagrams
State
Diagrams
Object
Diagrams
Scenario
Diagrams
Scenario
Diagrams
Statechart
Diagrams
Use Case
Diagrams
Use Case
Diagrams
Sequence
Diagrams
State
Diagrams
State
Diagrams
Class
Diagrams
Activity
Diagrams
Models

USE CASE DIAGRAM
 Outsider's view of a system.
 Emphasizes on what a system does rather than how.
 Use case diagrams are the collection of scenarios.
 A scenario is an example of what happens when someone(Actor)
interacts with the system.
 Scenarios together accomplishes a specific goal of the user.
 Every use case diagram has actors, use cases, and communications.

Use Case Modeling: Core Elements
Introduction to UML
10
Construct Description Syntax
use case A sequence of actions, including
variants, that a system (or other
entity) can perform, interacting with
actors of the system.
actor A coherent set of roles that users
of use cases play when interacting
with these use cases.
system
boundary
Represents the boundary between
the physical system and the actors
who interact with the physical
system.
UseCaseName
ActorName

Use Case Modeling: Core Relationships
Introduction to UML
11
association The participation of an actor in a use
case. i.e., instance of an actor and
instances of a use case communicate
with each other.
extend A relationship from an extension use
case to a base use case, specifying
how the behavior for the extension
use case can be inserted into the
behavior defined for the base use
case.
generalization A taxonomic relationship between a
more general use case and a more
specific use case.
<<extend>>

Use Case Modeling: Core Relationships (cont’d)
Introduction to UML
12
include An relationship from a base use case
to an inclusion use case, specifying
how the behavior for the inclusion use
case is inserted into the behavior
defined for the base use case.
<<include>>

Use Case Relationship

Extend and Include Relationship
we can add extend relationships to a model to show the following situations:
 A part of a use case that is optional system behavior
 A subflow is executed only under certain conditions
 A set of behavior segments that may be inserted in a base use case
Include Relationship
 The behavior of the inclusion use case is common to two or more use cases.
 The result of the behavior that the inclusion use case specifies, not the behavior itself,
is important to the base use case.

Example :Use Case Diagram
Introduction to UML
15

USE CASE DIAGRAM
Use case diagrams are helpful in three areas.
determining features (requirements).
New use cases often generate new requirements as the
system is analyzed and the design takes shape.
communicating with clients.
Their notational simplicity makes use case diagrams a good
way for developers to communicate with clients.
generating test cases.
The collection of scenarios for a use case may suggest a suite
of test cases for those scenarios.

CLASS DIAGRAM
 Structural overview of a system by showing its classes and the relationships
among them
 Static diagrams
Static relations:
 Associations
 Subtypes
Static structure:
 Attributes
 Operations
 Created along with use case diagrams
 Transition from what? to How?

CLASS DIAGRAM- Class
The illustration uses the following UML™
conventions.
• Static members are underlined. Instance
members are not.
• The operations follow this form:
<access specifier> <name> ( <parameter list>) :
<return type>
•The parameter list shows each parameter type
preceded by a colon.
• Access specifiers appear in front of each
member.

CLASS DIAGRAM
Class information: visibility and scope
 Attributes and operations can be labeled according to access and
scope
Symbol Access
+ public
- private
# protected

Class Operations
 An operation is the implementation of a service that can be requested from any
object of the class in order to affect behaviour.
 Used to manipulate the attributes or to perform other actions.
 Operations are normally called functions, but they are inside a class and can be
applied only to objects of that class.
 Signature - return-type, a name and zero or more parameters.
 The signature describes everything needed to use the operation.

Example : Class Diagram

Class-Association
 Associations are structural relationships where instances (objects) of one class
are connected to instances (objects) of another class.
 an employee works for a company
 a company has a number of offices
 An association is normally bidirectional, which means that if an object is
associated with another object, both objects are aware of each other (navigation
is bidirectional by default).
 Binary association connects exactly two classes.
 The most common association is just a connection between classes.

Association adornments: name, role
 The association has a name - the descriptive term, often a verb, for the
association.
 Each association has two association ends; each end is attached to one of the
classes in the association. An end can be explicitly named with a label. This
label is called a role name (association ends are often called roles).

Reflexive Associations
 A class has an association to itself.
 Example: A directory may contain other directories.
Directory File
0..1
parent
subdirectory
0..*
1 0..*

Class Navigability
 A navigability arrow on an association shows which direction the association
can be traversed or queried.

Class Associations: multiplicity
 Multiplicity defines the number of
objects associated with an instance of
the association.
 Default of 1 (1: 1)
 0 or 1: 0..1
 Zero or more (0..infinite): *
 1 or more (1..infinite): 1..*
 n..m; range from n to m inclusive
Car Person
transports
passenger
Car Person
transports
passenger
5
Car Person
transports
passenger
*
Car Person
transports
passenger
1..*
Car Person
transports
passenger
2..5

Class - Generalization
 A specialization / generalization relationship, in which objects of the
specialized element (child) are substitutable for objects of the
generalized element (parent).
 Superclass – the generalization of another class, the child.
 Subclass – the specialization of another class, the parent.
V
ehicle
WindPowered
V
ehicle
MotorPowered
V
ehicle
Land
Vehicle
Water
V
ehicle
venue
venue
power
power
Sailboat
Truck
{overlapping} {overlapping}

Generalization - characteristics
 Identify common features concerning behaviour and
knowledge. Define these common features on a higher level in
the inheritance hierarchy.
 The aim is at behaviour more than knowledge when combining
classes.
 Generalization is a bottom-up process.
 A superclass includes all common properties of its subclasses.

Specialization - characteristics
 Define a new class which is a special appearance of an
existing class.
 Specialization is a top-down process.
 A subclass can have attributes and operations that are
specific for that sub-class.
 A subclass may redefine operations of its super-class

Class Diagram - Constraints
 The basic constructs of association, attribute, and
generalization do much to specify important constraints.
 They cannot indicate every constraint. These constraints
still need to be captured; the class diagram is a good place
to do that.
 The UML allows you to use anything to describe
constraints. The only rule is that we put them inside braces
{ }.

CONSTRAINTS

Aggregation and Composition
 Associations in which an object is part of a whole are aggregations.
 Composition is a strong association in which the part can belong to
only one whole -- the part cannot exist without the whole.
Composition is denoted by a filled diamond at the whole end.
Computer system
Monitor
Building
Floor
1
1
1
1..*

Aggregation and Composition

Alternative Notation for Composition

Advanced Class Concepts : Abstract
 An operation is abstract if it has no implementation.
 A abstract class cannot have any direct instances.
 Abstract classes only occur in the context of an inheritance
hierarchy.
 Abstract operations and classes are specified by writing its
name in italics.

Advanced Class Concepts : Abstract cont.

Class Diagram with Interfaces

Package Diagram
 To simplify complex class diagrams, we can group classes into
packages. Packages.
 Packages appear as rectangles with small tabs at the top.
 The package name is on the tab or inside the rectangle.
 The dotted arrows are dependencies.

PACKAGE DIAGRAM

Interaction : Sequence Diagram
 Sequence diagrams and Collaboration diagrams
 Class and object diagrams are static model views. Interaction
diagrams are dynamic. They describe how objects collaborate.
 A sequence diagram is an interaction diagram that details how
operations are carried out -- what messages are sent and when.
 Sequence diagrams are organized according to time. The time progresses
as we go down the page.
 The Sequence diagram lists objects horizontally, and time vertically, and
models these messages over time.

Sequence Diagram : Drawing Elements
 Diagram Header Elements
 Actor Represents an external person or entity that interacts with the system
 Object Represents an object in the system or one of its components
 Unit Represents a subsystem, component, unit, or other logical entity in the
system (may or may not be implemented by objects)
 Separator Represents an interface or boundary between subsystems,
components or units (e.g., air interface, Internet, network)
 Group Groups related header elements into subsystems or components being modeled and
are laid out horizontally at the top of the diagram.

Sequence Diagram Body Elements
 Message
 Synchronous Message
 Asynchronous Message
 Create Message
 Destroy Message
 Action

Sequence Diagram Body Elements
 Block(Loop or Conditional)
 Page Break
 Return Message
 Free Note
 Flow Note
 Diagram links

Interaction : Sequence Diagram

Sequence Diagram-Example

SEQUENCE DIAGRAM

Usage of Sequence Diagram
 Complex interactions between components
 components are being developed in parallel by different teams
 Supporting Robust interface covering multiple scenarios
 Use case elaboration
 can be used to flesh out the details of one or more use cases

COLLABORATION DIAGRAM
 Type of an interaction diagram.
 Collaborates the static and dynamic relationship
 Focus on Object Roles rather than timing.
 Each message in a collaboration diagram has a sequence number.
 The Collaboration diagram may be used to:
 Describe a specific scenario by depicting the movement of messages between the objects
 Show a spatial organization of objects and their interactions, rather than the sequence of
the interactions

COLLABORATION DIAGRAM

Sequence Diagram
Reserving a copy of book in Library

Collaboration Diagram
Reserving a copy of book in Library

STATE CHART DIAGRAM
 Objects have behaviors and state.
 The state of an object depends on its current activity or condition.
 A statechart diagram shows the possible states of the object and the
transitions that cause a change in state.
 Our example diagram models the login part of an online banking system.
Logging in consists of entering a valid social security number and personal id
number, then submitting the information for validation.
 Logging in can be factored into four non-overlapping states: Getting SSN,
Getting PIN, Validating, and Rejecting. From each state comes a complete
set of transitions that determine the subsequent state.

State Chart Diagram – Dial Tone

STATE CHART DIAGRAM - Login

STATE CHART DIAGRAM
 States are rounded rectangles.
 Transitions are arrows from one state to another.
 Events or conditions that trigger transitions are written
beside the arrows.
 Uses
 The life history of a given class, usecase, operation
 The events that cause a transition from one state to another
 The actions that result from a state change

ACTIVITY DIAGRAM
 An activity diagram is essentially a fancy flowchart.
 Activity diagrams and statechart diagrams are related.
 Statechart diagram focuses attention on an object
undergoing a process (or on a process as an object).
 An activity diagram focuses on the flow of activities
involved in a single process. The activity diagram shows the
how those activities depend on one another.

Element and its description Symbol
Initial Activity: This shows the starting point or first activity of
the flow.
Activity: Represented by a rectangle with rounded (almost oval)
edges.
Decisions: Similar to flowcharts.
Signal: When an activity sends or receives a message, that activity
is called a signal. Signals are of two types: Input signal (Message
receiving activity) shown by a concave polygon and Output signal
(Message sending activity) shown by a convex polygon.
Concurrent Activities: Some activities occur simultaneously or
in parallel. Such activities are called concurrent activities. For
example, listening to the lecturer and looking at the blackboard is a
parallel activity. This is represented by a horizontal split (thick dark
line) and the two concurrent activities next to each other, and the
horizontal line again to show the end of the parallel activity.
Final Activity: The end of the Activity diagram is shown by a
bull's eye symbol, also called as a final activity.

ACTIVITY DIAGRAM

Activity Diagram - Example

Implementation diagrams
 Show aspects of model implementation, including source
code structure and run-time implementation structure
 Kinds
 component diagram
 deployment diagram

Component Diagram
Introduction to UML
62
 Shows the organizations and dependencies among software
components
 Components include
 source code components
 binary code components
 executable components

Elements of component diagram
Element and its description Symbol
Component: The objects interacting with
each other in the system. Depicted by a
rectangle with the name of the object in it,
preceded by a colon and underlined.
Class/Interface/Object: Similar to the
notations used in class and object diagrams
Realization/Association: Similar to the
relation/association used in class diagrams

Component Diagram

Deployment Diagram
Introduction to UML
65
 Shows the configuration of run-time processing
elements and the software components, processes
and objects that live on them
 Deployment diagrams may be used to show which
components may run on which nodes

Deployment Diagram

The Current Official UML Specification:
The current official version of UML and its associated specifications can be
downloaded from OMG Specifications Catalog page for Modeling and Metadata
Specifications at
http://www.omg.org/technology/documents/modeling_spec_catalo
g.htm#UML

UML Certification
OCUP
OMG Certified UML Professional
Three Certification Levels:
 OCUP Fundamental
 OCUP Intermediate
 OCUP Advanced
Link : http://www.omg.org/uml-certification/

References
 Web References :
 http://www.uml.org/
 http://dn.codegear.com/article/31863
 http://www-128.ibm.com/developerworks/rational/library/3101.html
 http://www.andrew.cmu.edu/course/90-754/umlucdfaq.html
 Book References :
 UML Distilled by Martin Fowler with kendall Scott, Pearson Education.
 User Guide for UML by Grady Booch, Ivar Jacobson and James Rumbaugh

UML Class and Use Case Diagrams

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