Object Oriented Analysis and Design

SYSTEM ANALYSIS AND DESIGN

Object-Oriented Analysis
and
Design

1

Learning Objectives
 Key terms
 Association
 Class diagram
 Event
 Object
 Object class
 Operation
 Sequence diagram
 State
 State transition
 Unified Modeling Language (UML)
A.2  Use case 2

Learning Objectives (continued)

 Discuss the concepts and principles underlying
the object-oriented approach.
 Learn to develop requirements models using
use-case diagrams.
 Learn to use class diagrams to develop object
models of the problem domain.
 Learn to develop requirements models using
state and sequence diagrams.

A.3 3

The Object-Oriented Modeling Approach
● Benefits
1.The ability to tackle more challenging problem
domains
2.Improved communication among users,
analysts, designers, and programmers
3.Reusability of analysis, design, and
programming results
4.Increased consistency among the models
developed during object-oriented analysis,
design, and programming
A.4 4

The Object-Oriented Modeling Approach
(continued)
● Object-Oriented Systems Development Life
Cycle
– Process of progressively developing
representation of a system component (or
object) through the phases of analysis,
design, and implementation
– The model is abstract in the early stages
– As the model evolves, it becomes more and
more detailed

A.5 5

The Object-Oriented Systems
Development Life Cycle
● Analysis Phase
– Model of the real-world application is
developed showing its important properties
– Model specifies the functional behavior of the
system independent of implementation details
● Design Phase
– Analysis model is refined and adapted to the
environment
● Implementation Phase
– Design is implemented using a programming
language or database management system
A.6 6

The Object-Oriented Systems Development Life Cycle
(continued)
● Unified Modeling Language (UML)
– A notation that allows the modeler to
specify, visualize and construct the artifacts
of software systems, as well as business
models
– Techniques and notations
• Use cases
• Class diagrams
• State diagrams
• Sequence diagrams
A.7 7

Use-Case Modeling
● Applied to analyze functional requirements of
the system
● Performed during the analysis phase to help
developers understand functional
requirements of the system without regard for
implementation details
● Use Case
– A complete sequence of related actions
initiated by an actor
● Actor
– An external entity that interacts with the
system
A.8 8

Use-Case Modeling
● Use cases represent complete functionality of
the system
● Use cases may participate in relationships with
other use cases
● Use cases may also use other use cases

A.9 9

Object Modeling: Class Diagrams
● Object
– An entity that has a well-defined role in the
application domain, and has state, behavior,
and identity
● State
– A condition that encompasses an object’s
properties and the values those properties have
● Behavior
– A manner that represents how an object acts
and reacts
● Object Class
– A set of objects that share a common structure
A.11 and a common behavior 11

Object Modeling:
Class Diagrams (continued)
● Class Diagram
– Class is represented as a rectangle with three
compartments
– Objects can participate in relationships with
objects of the same class

A.12 12

Object Modeling:
Object Diagrams
● Object Diagram
– A graph of instances that are compatible with a
given class diagram; also called an instance
diagram
– Object is represented as a rectangle with two
compartments
● Operation
– A function or service that is provided by all the
instances of a class
● Encapsulation
– The technique of hiding the internal
implementation details of an object from its
external view
A.13 13

Representing Associations
● Association
– A relationship between object classes
– Degree may be unary, binary, ternary or higher
– Depicted as a solid line between participating
classes
● Association Role
– The end of an association where it connects to
a class
– Each role has multiplicity, which indicates how
many objects participate in a given association
relationship
A.15 15

Representing Generalization
● Generalization
– Abstraction of common features among
multiple classes, as well as their relationships,
into a more general class
● Subclass
– A class that has been generalized
● Superclass
– A class that is composed of several generalized
subclasses
A.17 17

Representing Generalization (continued)

● Discriminator
– Shows which property of an object class is
being abstracted by a generalization
relationship
● Inheritance
– A property that a subclass inherits the features
from its superclass
● Abstract Class
– A class that has no direct instances but whose
descendents may have direct instances
● Concrete Class
– A class that can have direct instances
A.18 18

Representing Aggregation
● Aggregation
– A part-of relationship between a component object and
an aggregate object
– Example: Personal computer
• Composed of CPU, Monitor, Keyboard, etc

A.20 20

Dynamic Modeling: State Diagrams
● State
– A condition during the life of an object during
which it satisfies some conditions, performs
some actions or waits for some events
– Shown as a rectangle with rounded corners
● State Transition
– The changes in the attributes of an object or in
the links an object has with other objects
– Shown as a solid arrow
– Diagrammed with a guard condition and action
A.21
● Event 21
– Something that takes place at a certain point in

Dynamic Modeling:
Sequence Diagrams
● Sequence Diagram
– A depiction of the interaction among objects
during certain periods of time
● Activation
– The time period during which an object
performs an operation
● Messages
– Means by which objects communicate with
each other
A.23 23

Dynamic Modeling:
Sequence Diagrams (continued)
● Synchronous Message
– A type of message in which the caller has to
wait for the receiving object to finish executing
the called operation before it can resume
execution itself
● Simple Message
– A message that transfers control from the
sender to the recipient without describing the
details of the communication

A.24 24

Moving to Design

● Start with existing set of analysis model
● Progressively add technical details
● Design model must be more detailed than analysis
model
● Component Diagram
– A diagram that shows the software components or
modules and their dependencies
● Deployment Diagram
– A diagram that shows how the software components,
processes and objects are deployed into the physical
architecture of the system

A.26 26

Summary

● Object-Oriented Modeling Approach
– Benefits
– Unified Modeling Language
• Use cases
• Class diagrams
• State diagrams
• Sequence diagrams
● Use Case Modeling

A.28 28

Summary (continued)

● Object Modeling: Class Diagrams
– Associations
– Generalizations
– Aggregation
● Dynamic Modeling: State Diagrams
● Dynamic Modeling: Sequence Diagrams
● Moving to Design

A.29 29

● THANKS FOR ALL

30

Object Oriented Analysis and Design

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