I'm not sure if you are trying to make a performance  comparison or choose a technology for mediation utility  but either way the options in the list do not seem to be categoriezed correctly. I do not see OSSJ falling under the same category as RMI and Corba. OSSJ is a framework for OMC applications, unless you want to use the messaging introduced in its API suite which you needed to only mention the relevant messaging mechanism such as JMS, because OSSJ is completley J2EE driven

the same comment on SOAP, cause it is not a service invokation method, it is only a high level messaging protocol and is only suitable for certain interfaces

having said that I can only make a guess on what a "mediation utility" is by looking at the term you used, I can assume it probably needs to communication with different technologies, and that would lead to Corba, and if I made the right guess then you don't need to go towards making a comparison on performance KPIs any more