Server networks communicating via inter-user shared variables

Abstract

Server networks are generalized networks of asynchronous software processes interconnected by prescribed communication links according to prescribed protocols. As large-system-integration tools, they facilitate a divide-and-conquer approach, separating large software system development problems into a set of smaller problems programmed-in-the-small via standard software techniques within the confines of each server's virtual machine. In addition, server networks, programmed-in-the-large, knit together the solutions to these smaller problems. This paper presents the concepts of a server-network methodology that includes inter-server communication, the provision of and subscription to utility services, and the data-driven control-flow (DDCF) of server networks, which makes the remote dynamic reconfiguration of server networks possible through graphical programming. A server-network generator (SNG), which is an expert system that facilitates the graphical configuration, modification, and archival of server networks, is presented. Our APL2 implementation of server networks, including the implementation of utility services as generic building blocks, is described. Enhancements to the APL2 system services, which would benefit the future of server-network research and its application to production system management through horizontal integration of the factory floor and cooperative processing among networks of mainframes and engineering workstations running the VM/370 operating system, are presented.