Software reuse and interoperability have long been the Holy Grail of the simulation community. The current state-of-the-art interoperability standard in simulation is the High Level Architecture (HLA). HLA is a US DoD mandate and an IEEE standard. It has generated much interest among simulation researchers and practitioners, but whether it will gain widespread acceptance by the mainstream simulation community depends on its ability to support the mainstream approaches and techniques. Jini and XML are two emerging technologies that will potentially have tremendous impact on the solutions to the reuse and interoperability problems in the simulation domain. This paper proposes the use of Jini and XML in building an open and flexible framework for a federated simulation system. It also presents the design and development of a prototype XMLbased messaging system that is oriented towards our proposed system. A finding of our research is that Jini and XML may well complement each other in achieving interoperability between distributed components. Together, they constitute a promising infrastructure technology for future distributed systems.