Bakery Algorithms
نویسنده
چکیده
An approach to proving higher level properties of distributed protocols is suggested here in which a proof consists of two stages: In the higher-level stage, abstract properties of system executions are assumed and their desired consequences are proved. At the lower-level stage these abstract properties are shown to hold in every execution of the protocol. The paper studies the Bakery Algorithm of Lamport and some variants (these are all mutual exclusion protocols), and its main contribution is a protocol which is similar to the Bakery Algorithm but only uses bounded values. Another variant uses local clocks to coordinate the protocol's execution, and conditions on the clocks are determined that suuce for the protocol's correctness. In what sense is our bounded algorithm similar to the unbounded Bakery Algorithm? In that both satisfy the \Bakery Deenability prop-erty" (which is a strong form of the First Come First Serve property). An advantage of this two stage approach is demonstrated by the correctness proofs given to these variants of the Bakery Algorithm: Since they are shown to share with the Bakery Algorithm the same higher-level properties, their correctness proofs are reduced to only one stage (the lower level).
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