Real-time distribution middleware from the Ada perspective

Standards for distribution middleware sometimes impose restrictions and often allow the implementations to decide on aspects that are fundamental to the correct and efficient behaviour of the applications using them, especially when these applications have real-time requirements. This work presents a study of two standard approaches for distribution middleware that can be used from Ada applications: RT-CORBA, and the Distributed Systems Annex (DSA) of Ada. The study focuses on the problems associated with the real-time behaviour of some implementations of these approaches, and on possible solutions that can be derived from our experience with Ada implementations. Moreover, the paper considers the problem of integration of the distribution middleware with a new generation of scheduling mechanisms based on contracts.