1. CORBA: An Overview
Mojtaba Hosseini

2. Outline Motivation Introduction to CORBA Evolution of CORBA CORBA Core
Interoperability and internetworking
Conclusion

3. Motivation Applications working under different environments
Operating System
Programming Language
Distributed applications such as IP telephony must communicate
Over different network protocols
How can these applications work together?

4. Interoperability Problem
Mac OS
Windows OS
Smalltalk IP
Telephony
Application
Java IP Telephony Application ? ?
Network architectures and standards (SIP, ISDN, IP, ATM, etc)
Linux OS
C++ IP Telephony Application

5. Introduction to CORBA Common Object Request Broker Architecture
Interface Definition Language (IDL), Object model and Object Request Broker (ORB) as key elements
Main idea: provide standardized interfaces for transparent requesting/providing of services

6. into skeleton for object
Main Idea Behind CORBA
Object: entity
providing service
Client: entity
requesting service
Interface compiled
into skeleton for object
Interface compiled
into stub for client
ORB takes request
from client
ORB informs object
of service
Client requests service without knowing where provider is and in what environment (programming language, operating system)
Object provides service without knowing about the client’s environment or location

7. Evolution of CORBA Real-time Fault Tolerance Horizontal, Vertical
Facilities
Interoperability
CORBA Core
1991
1996
1998
1999
Real-time
Fault Tolerance
Horizontal,
Vertical
Facilities
Interoperability
Networking
IDL, Object
Model, ORB

8. CORBA Object Model

9. Schedule CORBA IDL Dynamic Invocation ORB Interface Object Adaptor
Interoperability
New features

10. IDL IDL used to define service interface
IDL is defined just like any programming language:
defines keywords (e.g. “void”)
literals (e.g. character literal ‘x’)
Identifiers (e.g. int numb)
restrictions on these (e.g. identifier can’t start with a number)

11. IDL Grammar IDL also defines a grammar
IDL can then be mapped into executable programming languages such as Java/C++

12. Schedule CORBA IDL Dynamic Invocation ORB Interface Object Adaptor
Interoperability
New features

13. Dynamic Invocation and Skeleton
IDL stub/skeleton not the only way to request/provide services
What if we don’t know about the interface at compile time? But we know what service we want to request?
Need Dynamic Invocation

14. Dynamic Invocation
Client defines “signature” of service: name, parameters, return value, context
ORB gives this to the object and object determines which method to invoke
Useful for providing different interfaces for the same service

15. Dynamic Invocation Example
Three telephone call charging policies:
Depending on originating/terminating location
Depending on terminating location only
Constant billing
Client
Dynamic
Invocation
Interface
Skeleton
charge(x,y)
Charge(y)
Charge()
charge(y)

16. Schedule CORBA IDL Dynamic Invocation ORB Interface Object Adaptor
Interoperability
New features

17. ORB Interface Provides common interfaces such as:
ORB operations: shutdown, initialize
Object operation: are two objects equivalent?
Policy operation: deny/allow services
Policy Management: overriding policies
ORB exceptions: no implementation available

18. Schedule CORBA IDL Dynamic Invocation ORB Interface Object Adaptor
Interoperability
New features

19. Portable Object Adaptor
Allow for multiple object implementations to exist on server side (e.g. multiple billing services for several companies)
VendorA
Billing Service
VendorB
Billing Service
Choose billing Service based on policy

20. Schedule CORBA IDL Dynamic Invocation ORB Interface Object Adaptor
Interoperability
New features

21. GIOP/IIOP Multiple vendors implementing ORBs
A need for ORBs to interface with one another in a standard way: General Inter-ORB Protocol
GIOP: generic protocol, no implementation
IIOP (Internet Inter-ORB Protocol) is the TCP/IP implementation of GIOP

22. CORBA and Interoperability
Mac OS
Windows OS
Smalltalk IP
Telephony
Application
Java IP Telephony Application
ORB
ORB
GIOP
GIOP
Network architectures and standards (SIP, ISDN, IP, ATM, etc)
Linux OS
ORB
C++ IP Telephony Application

23. Schedule CORBA IDL Dynamic Invocation ORB Interface Object Adaptor
Interoperability
New features

24. More Recent CORBA features
Domains such as Transportation, Health Care, Finance, etc. developed IDL interface common in their domain
CORBA standardized these for the domains
More recent CORBA versions include
Real-time capabilities
Fault-tolerance

25. Conclusion
There exist different environments in which telephony applications operate
There is a need for these applications to be interoperable
CORBA provides the standard way of doing so