Fragmented Objects for Distributed Abstractions

Fragmented Objects (FOs) extend the object concept to a distributed environment. The abstract view of a FO is a single, shared object, of which the distribution is hidden to clients. In the concrete view the FO designer controls (if wished) the distribution of data and function and of the communication between fragments. FO programming is supported by the FOG language, an extension of C++, and by a toolbox of predefined FOs. The FOG compiler ensures distributed type-safety of both the external and internal interfaces, verifies the encapsulation of FO instances, and automatically generates whatever coercions are necessary for marshalling/unmarshalling between layers. Currently, the toolbox contains mainly classes of primitive FOs such as RPC and multicast communication channels. We present the basic fragmented object concepts, the toolbox of predefined FOs, the FOG language and its compiler. We also present an example of a distributed application, the SOS Naming Service, structured as FOs. Finally, we point out the benefits of the FO approach