This paper describes PARDIS, a system containing explicit support for interoperability of PARallel DIStributed applications. PARDIS is based on the Common Object Request Broker Architecture (CORBA) [15]. Like CORBA, it provides interoperability between heterogeneous components by specifying their interfaces in a meta-language, the CORBA IDL, which can be translated into the language of interacting components. However, PARDIS extends the CORBA object model by introducing SPMD objects representing data-parallel computations. SPMD objects allow the request broker to interact directly with the distributed resources of a parallel application. This capability ensures request delivery to all the computing threads of a parallel application and allows the request broker to transfer distributed arguments directly between the computing threads of the client and the server. To support this kind of argument transfer, PARDIS defines a distributed argument type — distributed sequence — a genera...