Smart devices, such as personal assistants, mobile phone or smart cards, continuously spread and thus challenge every aspect of our lives. However, such environments exhibit spe-ci c constraints, such as mobility, high-level of dynamism and most often restricted resources. Traditional middle-wares were not designed for such constraints and, because of their monolithic, static and rigid architectures, are not likely to become a t. In response, we propose a exible micro-ORB, called Flex-ORB, that supports on demand export of services as well as their dynamic deployment and reconguration. Flex-ORB supports mobile code through an intermediate code representation. It is built on top of Nevermind, a exi-ble minimal execution environment, which uses a re exive dynamic compiler as a central common language substrate upon which to achieve interoperability. Preliminary performance measurements show that, while being relatively small (120 KB) and dynamically adapt-able, FlexORB outperforms traditional middlewares such as RPC, CORBA and Java RMI. 1.

While Java has become a de facto standard for mobile code and distributed programming, it is still a rigid and closed execution environment. Not only does this lack of flexibility severely limit the deployment of innovations, but it imposes artificial constraints to application developers. Therefore, many extensions to the JVM have been proposed, each of them dealing with specific limitations, such as emerging devices (mobile phones, smart cards), or constraints (real-time, fault tolerance). It leads to a proliferation of ad hoc solutions requiring the design of new virtual machines. Furthermore, those solutions are still rigid, closed and poorly interoperable.

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virtual machines: the JnJVM