The last decades have seen the emergence of the sea of objects paradigm for structuring complex distributed systems on workstations and local area networks. In this approach, applications and system services are composed of and communicate among themselves through reliable and transparently accessible object interfaces, leading to the interaction of hundred or thousands of unstructured objects.

This approach has lead to major progress in software composability and reliability. Unfortunately, it is based on a number of assumptions that do not hold on wide area networks. There, access to resources is intrinsically unreliable (because of failure, congestion, voluntary disconnected operation, etc.) and not transparent (because of variations in latency and bandwidth, hardware and software mobility, and the presence of firewalls). These characteristics are so radically different from the current computational norm that they amount to a new model of computation.

We discuss the challenges of computation on wide area networks. Our approach reflects the intuition that, to function satisfactorily on a wide area network, the sea of objects must be partitioned and made hierarchical, internally mobile, and secure. This paper is an abridged version of [3].