Legion The next logical step toward the world-wide virtual computer

1 The Opportunity The dramatic increase in ubiquitously available network bandwidth will qualitatively change how the world computes, communicates, and collaborates. The rapid expansion of the worldwide web, and the changes that it has wrought are just the beginning. As high bandwidth connections become available they " shrink " distance " and change our modes of computation, storage and interaction. Inevitably, users will operate in a wide-area environment that transparently consists of workstations, personal computers, graphics rendering engines, supercomputers, and non-traditional computing and rendering devices: TVs, toasters , etc. The relative physical location of the users and their resources will become increasingly irrelevant. The realization of such an environment, sometimes called a " metasystem " , is not without problems. Today's experimental high speed networks such the vBNS and the I-way preview both the promise and pitfalls. There are many difficulties: few approaches scale to millions of machines, the tools for writing applications are primitive, faults abound and mechanisms to handle them are not available, issues of security are treated in a patchwork manner, and site autonomy — controlling ones own resources while still playing in the global infrastructure —þis not addressed. As usual, the fundamental difficulty is software — specifically, we believe the problem is an inadequate conceptual model. In the face of the onrush of hardware, the community has tried to stretch an existing paradigm, interacting autonomous hosts, into a regime for which it was not designed. The result is a collection of partial solutions — some quite good in isolation, but lacking coherence and scalability — that make the development of even a single wide-area application demanding at best. Thus, the challenge to the computer science community is to provide a solid, integrated, conceptual foundation on which to build applications that unleash the potential of so many diverse resources. The foundation must at least hide the underlying physical infrastructure from users and from the vast majority of programmers, support access, location, and fault transparency, enable inter-operability of components, support construction of larger integrated components using existing components, provide a secure environment for both resource owners and users, and it must scale to millions of autonomous hosts. The technology to meet this challenge largely exists: (1) parallel compilers that support execution on distributed memory machines, (2) advances in distributed systems software that manage complex distributed environments, (3) the widespread acceptance of the object-oriented paradigm because of its encapsu-lation …