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Experience with Shared Object Support in the GUIDE System

P. Y. Chevalier, A. Freyssinet, D. Hagimont,
S. Krakowiak, S. Lacourte and X. Rousset de Pina
Bull-IMAG/Systmes, 2 av. de Vignate, 38610 Gires, France

Abstract

Support for co-operative distributed applications is an important direction of computer systems research involving developments in operating systems as well as in programming languages and databases. One emerging model for the support of co- operative distributed applications is that of a distributed shared universe organized as a set of objects shared by concurrent activities.

This paper describes our experience in the design, implementation, and use of a distributed system intended to support the above model. The system provides a generic interface designed to support any object oriented language that satisfies a minimal set of assumptions. Shared objects are grouped in clusters; a cluster is implemented as a persistent segment, which may be dynamically mapped in a context (virtual address space) associated with a task. Context dependent information (e.g. protection rights) associated with an object is lazily computed and stored in the context as a separate memory segment.

A prototype version of the system has been implemented on the Mach 3.0 microkernel as a base, and used for simple co-operative applications. Our implementation also demons trates how an object oriented platform can be supported alongside Unix on a modern microkernel.

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