A Report on CORBA and its Significance

written by Francis Chan (fchan@eecs.berkeley.edu)


Objective

Common Object Request Broker Architecture (CORBA) is a system definition specification that allows applications to communicate with one another regardless of their location, platform and developer. We have conducted a research on its architecture, impact and significance on the development of distributed applications. This serves as an inspiration and background study on how we should design our own architecture and protocols of the distributed design system that we plan to build.

Detailed Description

CORBA 2.0, together with the Interface Definition Language (IDL) and Application Programming Interfaces (API) that were defined by the Object Management Group, enables client/server object interaction and interoperability by specifying how Object Request Brokers (ORB) from different developers can interoperate.

Structure of the Object Request Broker Interfaces

The ORB is the middleware that establishes the client-server relationships between objects. Using an ORB, a client can transparently invoke a method on a server object, which can be on the same machine or across a network. The ORB intercepts the call and is responsible for finding an object that can implement the request, pass it the parameters, invoke its method, and return the results. The client does not have to be aware of where the object is located, its programming language, its operating system, or any other system aspects that are not part of an object's interface. In so doing, the ORB provides interoperability between applications on different machines in heterogeneous distributed environments and seamlessly interconnects multiple object systems. With an ORB, the protocol is defined through the application interfaces via a single implementation language-dependent specification, the IDL. In an ORB-based solution, developers simply model the existing component using the same IDL they use for creating new objects, then write "wrapper" code that translates between the standardized bus and the existing interfaces.

Significance of CORBA

Since the release of CORBA 1.0 in 1991, the promise to provide out-of-the-box multi-vendor interoperability among ORB implementations has yet been realized. The CORBA 1.2 specifications had many vague areas to allow a wide range of implementations, but caused problems with interoperability. The problem was finally resolved by CORBA 2.0 with the definition of a single wire-format which specifies how detailed information representing a CORBA request is laid out on a network transport. The wire-format to be adopted was: CORBA also standardized:

However, until conformance becomes commonplace, porting between different platforms, applications from ORB to ORB will remain limited.

CORBA provides a distributed object-oriented approach to integrating new as well as legacy applications and enables the developers to write an object wrapper to encapsulate the system. With CORBA, the developer needs only to write a description of the service provided by the system using IDL, then write code which invokes the appropriate set of actions in the system when one of the object wrapper's method in invoked.

CORBA Limitations

While the interoperability issue has been tackled in CORBA 2.0, the security aspects have not been sufficiently addressed, and this falls on the shoulders of the OMG Object Security Service Specification. These have been the major obstacles to serious and mission-critical applications development, particularly those who still employ legacy systems.

As a technology, CORBA is maturing rapidly and its specifications has received broad industry support. However, OMG technology has had only slow acceptance as OMG/CORBA technology is an object-oriented technology for distributed computing, an area where many users are not technically ready to apply and deploy in real environments. With the recent popularity of the Internet, the future of CORBA lies greatly in its use in open distributed tools and and services. This depends on both the publicity efforts on the part of OMG in encouraging software and system vendors to use CORBA and on CORBA's technical merits in enabling true compatibility among different platforms and other Internet programming languages and applications.

Status

We do not yet intend to fully integrate CORBA into our system but are watching closely external research and industry efforts in developing and using CORBA technology, especially those that provide the compatibility between Java and CORBA.

These research include:


References:

[1] http://coho.stanford.edu/~hassan/Java/Jylu/

[2] http://herzberg.ca.sandia.gov/jidl/