RMI-IIOP (read as "RMI over IIOP") denotes the Java Remote Method Invocation (RMI) interface over the Internet Inter-Orb Protocol (IIOP), which delivers Common Object Request Broker Architecture (CORBA) distributed computing capabilities to the Java platform.
In other words, it supports multiple platforms and can make remote procedure calls to execute, subroutines on another computer as defined by RMI.
The Java RMI-IIOP specification was created to simplify the development of CORBA applications, while preserving all major benefits.
RMI-IIOP uses generated code for remote objects and does not require supplementary classes for non-trivial data, unlike CORBA.
RMI-IIOP is largely based on the Object by Value concept that serves as a container or direct replacement for CORBA structures, unions, sequences, arrays and strings.