Toward Responsive Distributed Systems

Abstract

Computing environments in the next decade will be widely distributed, ever-changing, and ubiquitous. People will move with computers and will use them while moving. People will demand better user interfaces, so that they will be able to communicate with computers as if they are communicating with other people. For such purpose, we propose a hand-held computer called an Intimate Computer. It is a personified computer virtualizing the sincere spouse, reliable secretary, and/or dependable buddy of each individual. People will carry it, talk to it, and it will reply with a smile. It works an access terminal to a widely distributed computational resources. For such mobile computers to be materialized, we propose the Computational Field Model, which is a higher level abstraction of distributed computing systems. It is based on the notion of concurrent objects and provides an asynchronous and real-time computing environment.

In such a widely distributed computational environment, the notion of Responsive Systems shows different views from that of centralized systems. It is an open system which are shared by many people. Therefore, anything can happen in such an environment. We cannot premise any ”predictability in the system. We have try our best not to say that ”it is out of the specification, crash”. The real time feature is necessary because the system is connected with our everyday life. So as the feature of fault tolerance.

We propose an object-oriented framework for Distributed Responsive Systems. It is based on the notion of ”Best Effort and Least Suffering”. An object which receives a request does its best effort to satisfy the sender. On the other hand, an object which sends a request does its best to survive, or, in the other words, not to hang up. This is summarized as that an object as a server does its best effort while an object as a client does its least suffering. Since an object in a distributed system acts as a server and a client at the same time, each object has to provide the property of Best Effort and Least Suffering.

We have developed a real-time network protocol called RtP and real-time programming language to describe distributed systems called DROL based on the above mentioned notion. These attempts are our initial step toward true Distributed Responsive Systems, so that we can have responsive intimate computers in the responsive computational field.