Object Oriented Programming And GIS

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Object Oriented Programming And GIS

• Introduction To Computer Programming
• Object Oriented Programming (OOP)
• OLE Automation VBA
• ActiveX COM Technology
• Visual basic For Application(VBA)
• Application Of ESRI OOP Environments

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Object Oriented Programming In GIS

• Introduction Basic Concepts
• Computer
• Computer is a device that accepts information in
  the form of digital data and manipulates it for
  some result based on a sequence of instructions
  on how data is to be processed.
• Computer Programming
• Logic Development
• A question is said to be logical if it has the
  possibility of only two answers. The answer can
  either be Yes(1) or No(0), True(1) or False(0).
  Computer is composed of built in electrical
  circuits which either ALLOW(1) the flow of
  electric current or NOT(0). The circuit remains
  INACTIVE when NEITHER 0 NOR 1 condition is TRUE.
• 2 2 5 ???????
• In mathematics 22 is always 4 but through
  specific LOGIC Development we can obtain desired
  results from our computer program
• IF ab 4 THEN
• PRINT 5.

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Representing Program Algorithm

• Algorithm

The term algorithm (pronounced AL-go-rith-um) is
a procedure or formula for solving a problem. The
word derives from the name of the mathematician,
Mohammed ibn-Musa Al-Khowarizmi, who was part of
the royal court in Baghdad and who lived from
about 780 to 850. His work is the likely source
of Algebra.

• Pseudo Code
• Plain text language like English. Used for
  representation of Program Logic that can be
  transformed into any programming language. 
• Flow Chart
• Graphical representation of algorithm of the
  computer program.

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Example Of Pseudo Code

• PseudoCode Determine the class average for
  the first exam
•  Initialize variables
• -          total to zero
• -          counter to zero
•  
• Capture input, Sum up, and count the exam grades
• -          Input the first grade using sentinel
  value
• -          While the user has not as yet entered
  the sentinel
• o        Add entered grade into the total
• o        Add one to the grade counter
• o        Input the next grade
•  
• Calculate and print the average score
• -          If the counter is not equal to zero
• Set the average to the total divided by the
  counter
• Print average
• Else
• Print No grades were entered

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Example Of Flow Chart

• A program is required that will accept the cost
  of an order based upon a shipping option. And
  then a program will calculate a total cost. To
  do so, a customer must enter valid numbers.
  Also, a customer can select one of the shipping
  options, such as priority (14.95), express
  (11.95), and standard deliver (if the order is
  more than 75, then standard shipping is free
  otherwise it is 3.95).

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Application vs Programming Languages

• Application Software
•  Application software perform specific tasks
• Examples
• MS World, MS Excel, P Point
• ArcView, IDRISI ArcInfo
• Programming Languages
• Provides a solution developing environment
• Examples
• Java, VB, C, VC, MS Access, Oracle

• Two Paradigms Governs Program Construction

Process Oriented Model Object Oriented
Model Program is series of linear steps Splits
program into objects Code is applied on
data Data control access to Code Goto statement
control pointer Sets well defined interface to
Data
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• OOPS
• C, JAVA, VC, VB, Access, Oracle
• OOP Elements Code Data
• What is happening around ???
• Who is affected ???
• Code acts upon data

Object Oriented Programming
What Is Object ???
Object Inheritance
Object Properties
Object Instances
Object Methods
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Characteristics Of Object Oriented
Programming

• Abstraction
• Encapsulation
• Inheritance
• Polymorphism

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Abstraction

• Is Important Element OF OOP Concept
• Abstraction is Natural Concept.
• Human being manage complex problems through
  abstaraction.
• Example
• CAR is made of millions parts but we use it
  without considering its complex transmission
  systems.
• The concept of abstraction can be applied to
  computer programming. The data from a sequential
  or process oriented program can be transformed
  t he process of abstraction into its component
  objects.
• The sequence of each process step can become
  a collection of messages from these objects.
• ArcInfo Arcview fully implements the
  principle of abstraction while handling
• the spatial and non spatial data.
•  

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Encapsulation

• Encapsulation binds the Data and Code together in
  a wrapper
• Prevents it from external interference
• Eexcept a well defined interface
• Example
• The transmission and acceleration system of a car
• Can only be accessed through a well defined
  interface
• i.e the gear lever and the accelerator.

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Inheritance

• Inheritence is the process by which one object
  acquires the properties of the other
  keeping the hierarchical classification intact.
• Examples
• Toyota Corola car is an object of Toyota Cars.
  Toyota Cars belong to Car type of objects and
  cars belong to an automobile class. Thus each
  Corolla car implements the properties and methods
  of Car hierarchy and all cars implements the
  properties of automobiles CLASS.
• Arc View and ArcInfo implements graphics
  capabilities as properties and methods of CAD
  Software while its Database handling properties
  are inherited from DBMS.
• Inheritence makes programming easy.
• All Objects derives their common properties
  from their parent CLASS.

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Polymorphism

• Polymarphism facilitaes the use of one interface
  for a general class of objects.
• Examples
• In ArcView when you need to connect to the data
  base, you click a button and create an instance
  of an interface. Within the same interface you
  can connect to SQL, MS Access or execute ESRI
  standard data query. Thus you do not require
  separate instance for each or a separate
  interface for same type of operation.
• Example of Dogs
• They smell. The smell is an interface. But if
  the smell or interface is a cat , it will run
  after it immediately. However, if the smell or
  interface is of food it will move towards the
  bowl.
• Thus each interface is for a specific task to
  perform.
• In OOP an instance of an interface occurs for
  each type of task to perform.

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Object Linking Embedment(OLE)

• Visual Basic
• Visual Basic is highly successful object based
  programming Language.
• Its Integrated Development Environment is unique
  in facilitating programming operations.
• OLE in Visual Basic
• OLE lets Visual Basic(container) use the
  functionality of other applications (server).
• Other Applications include, MS Word, MS Excel, MS
  Outlook Express, MS Access, MS PPoint, Autodesk
  Autocad, AutoCad Map 2000 etc.
• Applications extends their functionality as set
  of CLASSES OBJECTS
• VB Programmers only make reference to CLASSES and
  OBJECTS.
• Examples
• Excel Worksheet object performs complex
  calculations within an application.
• Office Management application use Outlook object
  for communication.
• Autocad Drawing Design functionalities can be
  used within application.
• Advantages
• Complex Programming tasks are simplified by OLE.
• Multiple functionalities can be integrated into
  one application.
• OLE applications become part of the Operating
  System.
• One Window Operation.
• Linking Vs Embedment

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OLE Automation

• Visual Basic For Application(VBA)
• Microsoft Common Language and Programming
  environment for applications.
• VBA customizes applications, add capabilities to
  suit specific user environment.
• VBA does not develop applications
• But provides only the basic control structure,
  mathematical operators, string functions and
  variable manipulation power of Visual Basic to
  partner applications.
• Adds customization power to applications.
• VBA only facilitates customization and almost no
  analytical capabilities.
• The main power of development comes from the
  applications which uses VBA as programming
  environment
• Examples
• MS Word, MS Excell, ArcInfo, IDRISI, AutoCad etc.

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ActiveX Controls

• An OLE Object that Support customizable or
  programming interface
• Expose Properties, Methods and Events that are
  heart of OOP
• User cannot access or modify the code but can
  extend and combine
• Can manipulate data, customize application and
  enhance programs
• Usually developed in MS Visual C, MS Visual
  Basic and Java
• Platform Independent only need COM compliance
• Best suitable for distributed multi user
  environment
• Equally useful for stand alone desktop
  environment
• Can be a Textbox, Command Button, Audio Player,
  Video Player, Graphics Tool
• Advantages
• Reusability Of Software
• Platform Independence (To a larger extent
  requires COM compliance)
• Plug In functionality
• Data Security
• Data Integrity by transaction monitoring through
• Client Server Environment
• Basic ActiveX Control

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COMPONENT OBJECT MODEL or COM ?

• COM refers to both standard specifications and
  implementations. COM is a binary compatibility
  specification. Since runtime code is in binary
  format, therefore, COM component is compatible
  with binary system.
• COM defines binary specifications that are not
  reliant on any programming language.
• COM standards developed by Microsoft Corporation
  for adding interoperability and reusability of
  distributed Objects.
• Enables developers to build SYSTEMS by assembling
  reusable components from different vendors which
  communicate via COM Interfaces.
• COM is same to Developer as Protocol is to System
  Engineer.
• COM defines common APIs for diverse components to
  interact.
• DCOM and COM are COM extensions. DCOM allows
  networked based object interaction. COM
  integrates MTS and message queuing into COM.
• COM and DCOM represent "low-level" technology
  that allows components to interact, OLE, ActiveX
  and MTS represent higher-level application
  services that are built on top of COM and DCOM.
• Out Of Process Servers In Process Servers.

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Object Oriented Programming Using ESRI GIS

• GIS Application Development Using ArcInfo
• ArcInfo Uses 03 Levels Of Customization
• Level 1 Programming
• The simplest Level of ArcInfo Cutomization
• Involves no programming. Users can change the
  look and feel of ArcInfo applications
• For example Toolbars can be turned ON OFF using
  Customize Dialog.
• Map Printing Saving Facility can be turned ON
  and OFF.
• Level 2 Programming
• Uses built in Visual Basic For Application (OLE
  Automation)
• Developer can add new Menus and Tools and Work
  Flows to ArcInfo
• ArcMap and ArcCatalog includes built in VBA with
  Full fledge IDE debugging
• VBA Allows Addition of VB like Modules, Class
  Module user Forms to ArcInfo project files.
• Using VBA it is possible to create custom
  sophisticated application based on ArcObject
  frameworks.
• VBA is useful for small to medium sized
  applications.
• Applications cannot be deployed for use outside
  outside parent software
• Level 3 Programming
• Favorite development platform for experienced
  OOProgrammers
• Create reusable software building blocks Or new
  Applications
• Use Geo-spatial database Object Model

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What Is ArcObject Structure

• ArcMap ArcCatalog
• COM Based Technology
• ArcObjects can be customized with VB C
• Arc Object Offers about 1200 objects
• Basic Arc Object Structure

• MXDocument Represent a single Document i.e.
  IAcativeView
• SDI(ArcMap)
• MDI(Arc View)
• In Geographic View
• Active View Object is MAP
• In Layout View
• Active View Object is Page layout

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What ArObject Can Do?

• Extending ArcMap Arc Catalog
• Extending the Data model
• Embedding Within An Application
• Creating New Applications

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Extending ArcMap ArcCatalog

• ArcMap Arc Catalogue provides application
  framework which can be easily extended using
  ArcObject.
• Extemsions range from simple commands and tools
  to industry focused soloutions i.e.
• Customized Tools and
• User Interfaces

• Extending the Data model

• Specific behavior of object class to data model
  e.g
• Polygon behave differently with attribute data
  i.e.
• If constructed on mud or marsh or water body
• Polygon will be hatch according to an
  appropriate symbol
• And appropriate shape
• How this modular extension is Possible?????
• implementing drawing method
• checking the feature attributes
• running a logical loop
• arriving at a decision
• automatically re-drawing the polygon

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Creating New Applications

• Embedding Within An Application

• ArcObject being a COM compliant
• Any COM compliant application can embed
  ArcObjects
• Use of ArcObjects is Unlimited in the context of
  OLE technology
• Thus its uses are more than customizing ArcMap
  ArcCatalog
• Example
• Like ArcMap, MS Word comes with VBA (Native
  development environment)
• ArcViewer can be Linked and Embedded in MS World

• ArcObject being a COM compliant
• Beyond customization is creating new independent
  GIS applications
• Use ArcObjects in Visual Basic
• Can build dedicated GIS applications
• After deployment application lies over O.S
• Who can do it ???
• Visual Basic Developer or simply GIS specialist
• Developer decides aspects of
• Application Frame Work, Graphic User
  Interface(GUI) Program Control
• Dsitributed or Desktop Application ??
• Specific Cliental Focus and so
  on--------------------------------------?gtgtgtgtgt

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Where Next ???

• The goal of this presentation is to address
• The openness of OOP and ArcObjects
• Recommendations
• Start Learning Visual Basic for development
• Start Oracle for DBMS
• Java for Web based programming
• Conclusions
• The wealth of GIS functionality lies in OOP
• One do not need to study computer science for
  Programming
• Explore logic of existing programs
• Build your own simple Programs and debug
• You are surely a programmer of the future
• But Computer Programming !!!!
• has its own Psychology
• Some one said it is by default

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Questions