CORBA

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CORBA
Common Object Request Broker Architecture
taking objects a step further!
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• Rapid changes in HW and OS lead to advantages
  of client/server systems
• Result greater system complexity, user demand,
  management expectations
• Additional pressure from the necessity to
  maintain legacy systems

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Object Management Group, (OMG) formed in 1989
Focus on integration of systems and applications
across heterogeneous platforms
After soliciting input, CORBA standard was
defined and introduced in 1991
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CORBA
PROVIDES HIGH-LEVEL OBJECT ORIENTED INTERFACE!!!
The only REAL competitor is, of course
MICROSOFT DCOM
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CORBA
allows applications and their objects to
communicate with each other no matter where they
are and or who designed them!!
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• When introduced in 1991, CORBA defined the
  Interface Design Language, (IDL), and
  Application Programming Interface, (API)
• These allow client/server interaction within a
  specific implementation of an Object Request
  Broker, (ORB)

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IDL...
A technology independent syntax for describing
object encapsulation
ltspecificationgt ltdefinitiongt ltdefinitiongt
lttype_dclgt
ltconst_dclgt ltexcept_dclgt
ltinterfacegt
ltmodulegt
An example of the syntax
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CORBA...
it even has its own hello world!!
import HelloWorld. public class
HelloWorldImpl implements SimpleHelloWorldServan
t private final java.lang.String
myString "Hello World!" public
synchronized java.lang.String sayHello()
throws sunw.corba.SystemException
return myString
The first thing we must do is define the
interface to the serving object in OMG IDL
ifndef _HELLOWORLD_IDL define
_HELLOWORLD_IDL module HelloWorld
interface SimpleHelloWorld string
sayHello() endif
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ORB is middleware
Based on client/server model of distributed
computing, CORBA inserts a broker between
client and server
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Broker provides basic messaging and communication
between client and server, insulating
applications from the specifics of the system
configuration
Client transparently invokes methods on server,
either on same machine or across network
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The ORB

• intercepts calls

• finds object

• invokes method

• passes parameters

• returns results or error messages

REGARDLESS OF THE OBJECTS LOCATION, ITS
PROGRAMMING LANGUAGE OR EVEN THE OPERATING
SYSTEMS INVOLVED!!
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IDL generates stubs and skeleton programs for
each interface
Stub acts like a local function call, providing
interface to ORB
Skeleton is server side implementation of IDL
interface
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Skeletons and stubs
return the results and error messages
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The role of CORBA and the ORB are defined in the
Object Management Architecture
Included within the OMA are four object
categories
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The four categories of the OMA

• CORBAservices creation/movement of objects,
  queries/transactions, concurrency control,
  directory servi ces

• CORBAdomains are vertical market standards.
  For example financial, medical,
  telecommunications and manufacturing

• CORBAfacilities include compound document and
  system management. Both can be applied across
  multiple vertical domains for added
  functionality

• Applications user defined and proprietary
  interfaces

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The result?

• Programmer free to design system as they see
  fit, ORB defines application protocol via IDL

• Programmer free to choose language, environment
  and OS

• ORB allows integration of existing components
  into a network object architecture

• now possible to integrate existing systems with
  off-the- shelf products

CORBA...
represents the next step in software re-use