Object Oriented Analysis And Design

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Object Oriented Analysis And Design

• Overview

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What is an Object?

• A self-contained package, with specific variables
  (attributes) and methods (behaviors).
• An object stands alone.
• An objects implementation is purposely hidden
  from us.

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What is an Object?
Visual representation of a software object
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What is an Object?
A bicycle modeled as a software object
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What is a Class?

• A class is a blueprint or prototype that defines
  the variables and the methods common to all
  objects of a certain kind.

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What is a Class?

• Class is an implementation of an abstract data
  type and so encapsulates both data and
  operations.
• Object is run-time instance of class.
• Classes just sit there, objects do the real work.
• Memory is allocated for Objects not for Classes.

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What is a Message?

• The object to which the message is addressed
  (YourBicycle)
• The name of the method to perform (changeGears)
• Any parameters needed by the method (lowerGear)

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Example Object

• Description - provides time of day, and an
  audible indication of a user-defined time during
  the day
• Interface
• Inputs - time of day, alarm time
• Outputs - time of day, audible alarm
• Attributes
• hour hand, minute hand, second hand, bell
• Behaviors
• Increment hour, increment minute, increment
  second, sound bell

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Key Object-Oriented Characteristics

• Encapsulation (Information Hiding)
• Attributes and behavior are rolled into the
  object, and hidden from the rest of us. Only
  thing exposed is the public interface
• Inheritance
• Creating one object from another, already defined
  object, adding to its capabilities and public
  interface..
• Polymorphism
• Specific object behavior is determined within a
  run-time context. An object can morph itself
  based on the context in which it is currently
  used.
• Re-useable
• With very discrete and finite capabilities,
  objects can be used in other parts of the system,
  or within other systems.

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Clock Object

• How does our clock rate as an object?
• Encapsulation
• Provides hour, minutes and seconds, and an alarm.
• Do we know the mechanisms for incrementing hours,
  minutes and seconds? Sounding the alarm?
• Inheritance
• We can use our simple clock object to create
  additional, more complex objects requiring time.
  E.g., chronograph, washing machine timer
  controller, etc.
• Polymorphism
• Not applicable
• Re-usable
• Our clock can be used in thousands of
  applications as is. We can use it in any
  application that requires us to keep track of
  time, and alert us when a certain time has
  occurred.

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What is OOAD?

• Object Oriented Analysis Design is the art of
  developing systems based on a set of cooperating
  objects.
• This stuff is not an exact science. Anyone who
  tells you that is mistaken.
• Experience allows you to develop the craft, but
  it can never be mastered.
• Success depends upon systems analysis and
  software development teams understanding OOAD and
  available tools.
• Smooth and natural transition occurs between
  analysis and design teams due to nature of
  defined processes.

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What is OOAD?

• OOAD facilitates a variety of processes for
  analyzing and developing systems.
• A methodology.
• There is no right or wrong process to implement
  OOAD. Understanding the principles of OOAD, as
  well as the toolkits available, allows you to
  define or tailor your own process.
• The main advantage of OOAD is its integration of
  systems analysis and software development teams
  through process definition and modeling
  techniques available.

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Visual Modeling

• Modeling captures essential parts of the system.
  Visual modeling is modeling using standard
  graphical notations Dr. James Rumbaugh
• A picture is worth a thousand words. Ancient
  Proverb

Order
Business Process
Item
Ship via
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What is UML?

• UML stands for Unified Modeling Language
• The UML combines the best of the best from
• Data Modeling concepts (Entity Relationship
  Diagrams)
• Business Modeling (work flow)
• Object Modeling
• Component Modeling
• The UML is the standard language for visualizing,
  specifying, constructing, and documenting the
  artifacts of a software-intensive system.
• It can be used with all processes, throughout
  the development life cycle, and across different
  implementation technologies

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What is UML?

• The Unified Modeling Language is used to Specify,
  Visualize, Implement, Test and Document systems.
• UML captures the elements and artifacts of the
  development of object oriented systems and
  software.
• UML also facilitates the Specification and
  Visualization of ANY system (whether it appear as
  an object-oriented system or not).
• It is a visual modeling tool used to implement a
  process and methodology.

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What UML is NOT

• A process. Processes include
• Waterfall
• Spiral Development
• Incremental
• Agile
• etc.
• Proprietary
• UML is free to use and distribute. Third party
  vendors can build a tool based upon it without
  prior permission.
• Companies can use it in their design
  documentation without prior permission.

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Static Modeling

• This defines the non-changing characteristics of
  the system. For example
• What are the uses of the system?
• What are the relationships between uses in the
  system?
• What are the inputs and outputs, or interface to
  the system?
• What are the objects in the system and their
  relationships?
• How is the system deployed?

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Dynamic Modeling

• This defines the changing characteristics of the
  system. For example
• What are the various timing aspects of the uses
  of the system?
• What are the states, and circumstances of those
  states, that the objects in the system can be in
  at any particular time?
• How does the system behave over time as a result
  of the environment in which it is in?

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UML Static Diagrams

• Use Case
• Depicts functional capabilities, or uses, of the
  system.
• Class
• Depicts relationships and dependencies of classes
  in the system.
• Object
• Depicts relationships and dependencies of
  instantiated classes (I.e. objects) in the system.

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UML Static Diagrams

• Structure Diagrams
• Depicts the main components of the system
  (hardware, software, human) and the interfaces
  between.
• Package
• Depicts relationships and dependencies of
  high-level components in the system.
• Component
• Depicts relationships and dependencies of system
  components.
• Deployment
• Depicts how system components are implemented in
  hardware in the system.

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Use Case Diagram
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Class Diagram
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Object Diagram
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Structure Diagram
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Component Diagram
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Package Diagram
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Deployment Diagram
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UML Dynamic Diagrams

• Interaction Diagrams
• Depict timing of events and messages within Use
  Cases and classes in the system. They are
  interchangeable.
• Sequence
• Depicts timing of events in a sequential top to
  bottom, left to right fashion.
• Collaboration
• Depicts timing of events using a sequential
  numbering.

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UML Dynamic Diagrams

• State
• Depicts all the possible states that objects of
  the class can have, and which events cause the
  state to change.
• Activity
• Depicts the activities performed in an operation
  , though it can also be used to describe other
  activity flows, such as a use case or an
  interaction.

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Sequence Diagram
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Collaboration Diagram
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State Diagram
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Activity Diagrams
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Visual Modeling With Class Diagrams
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Class Diagram
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Activity Diagram
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Sequence Diagram
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Thoughts on OOAD/UML

• The OOAD methodology, and any process that uses
  it, will only work if the entire project team
  embraces it.
• Everyone from the Program Manager on down must be
  convinced of its utility.
• You cannot implement a system successfully unless
  the entire system is analyzed and developed in a
  consistent manner.
• As a minimum, the system must go through the
  Requirements and Analysis phases using Use Cases.
• More on this later.
• Most importantly, the systems and software teams
  must be an integrated team to gain the most
  benefits.

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Model Driven Architecture (MDA)

• An approach to system development using models as
  a basis for understanding, design, construction,
  deployment, operation, maintenance and
  modification
• Three essential elements
• specifying a system independently of the platform
  that supports it,
• specifying platforms,
• transforming the system specification into one
  for a particular choice of platform.
• Goals portability, interoperability and
  reusability
• Prescribes the kinds of model to be used in
  specifying a system, how those models are
  prepared and the relationships between them

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What MDA Does

• Identifies different viewpoints on a system
• different abstractions - reflecting different
  concerns
• providing a way of dealing with system complexity
• Specifies 3 kinds of viewpoint model for a
  system
• a computation independent model (CIM) a view of
  a system that specifies its function without
  specifying details of its structure
• a platform independent model (PIM) a view of a
  system that specifies its computational structure
  independent of any specific platform - usable
  with different platforms of similar type.
• a platform specific model (PSM) a view of a
  system that combines the specifications in the
  PIM with a specification of the use of a
  particular type of platform.
• Specifies transformations between models

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MDA Ultimate Goal?

• Complete, executable model.
• 100 automatic code generation from the model.
• Complete requirements, design and test
  information contained in models.

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UML Resources

• http//www.rational.com
• Rational site with a plethora of information
  about UML and the Rational process.
• http//www.omg.org/technology/documents/formal/uml
  .htm
• UML 2.0 specification