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Summary: Convergence Re nement
Murat Demirbas Anish Arora
Department of Computer and Information Science
The Ohio State University
Columbus, Ohio 43210 USA
Abstract
Re nement tools such as compilers do not necessarily
preserve fault-tolerance. That is, given a fault-tolerant
program in a high-level language as input, the output of
a compiler in a lower-level language will not necessarily
be fault-tolerant. In this paper, we identify a special class
of re nement, namely \convergence re nement", that pre-
serves the fault-tolerance property of stabilization. We
illustrate the use of convergence re nement by present-
ing the rst formal design of Dijkstra's little-understood
3-state stabilizing token-ring system. Our designs begin
with simple, high-atomicity token-ring systems that are
not stabilizing, and then add a high-atomicity \wrapper"
to the systems so as to achieve stabilization. Both the
system and the wrapper are then independently re ned
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