Hi Sachin
CORBA is an architecture.
It is basically a link to connect/communicate/interface application software running
on heterogenous platforms.
RMI also is an interface but it connects applications running on different servers but written totally in
Java.
EJB again is an architecture and applications written using EJBs work on any system that supports the EJB specs.
Middleware, is a layer of software between the network and the applications. This software provides services such as identification, authentication, authorization, directories, and security.
Please correct me if I am wrong. Appreciate it.
Suneel