2 Model Overview

This section provides an overview of the distribution model used in the BETA distribution library.

The distribution library provides the shellEnv application framework for developing distributed BETA programs. Methods in remote objects can be called the same way as methods in local objects. The programmer need not worry about low level communication aspects since shellEnv handles these automatically.

As a special case, the BETA distribution library makes it easy to implement client/server applications. Clients and servers are simply BETA objects residing in different processes, possibly on different network hosts. However, the client/server model is asymmetric in the sense that servers are not allowed to call methods in their clients. In contrast, with the BETA distribution library object relationships are not constrained to be asymmetric. This means that the server may call methods in the client as well as the client may call methods in the server.

The following sections provide a non-technical overview of the basic building blocks in the BETA distribution library. Later sections contain a detailed description of the library, and how to use it.

Figure 1: Ensembles, Shells and Remoteables