Guardians and actions

This paper presents an overview of an integrated programming language and system designed to support the construction and maintenance of distributed programs: programs in which modules reside and execute at communicating, but geographically distinct, nodes. The language is intended to support a class of applications in which the manipulation and preservation of long-lived, on-line, distributed data is important. The language addresses the writing of robust programs that survive hardware failures without loss of distributed information and that provide highly concurrent access to that information while preserving its consistency. Several new linguistic constructs are provided; among them are atomic actions, and modules called guardians that survive node failures.