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19th International Conference on Advanced Information Networking and Applications (AINA'05) Volume 1 (AINA papers) (2005)
Taipei, Taiwan
Mar. 25, 2005 to Mar. 30, 2005
ISSN: 1550-445X
ISBN: 0-7695-2249-1
pp: 961-966
Michel Raynal , IRISA / Université de Rennes
Matthieu Roy , LAAS-CNRS
Ciprian Tutu , Johns Hopkins University
A concurrent object is an object that can be concurrently accessed by several processes. Two well known consistency criteria for such objects are atomic consistency (also called linearizability) and sequential consistency. Both criteria require that all the operations on the concurrent objects can be totally ordered in such a way that each read operation obtains the last value written into the corresponding object. They differ in the meaning of the word "last" that refers to physical time for atomic consistency, and to logical time for sequential consistency. This paper investigates the merging of these consistency criteria in a multiprocess program. The proposed combination offers two read operations to the processes, namely, an atomic read operation and a sequentially consistent read operation. While the first provides a process with the last "physical" value of an object, the second provides it with a value that is approximate with respect to real-time but whose semantics is perfectly well defined. A protocol that implements the combination on top of an asynchronous distributed system is described. The protocol provides a better understanding of the similarities and differences between these consistency criteria. Moreover, the protocol is generic in the sense that it can be tailored to provide only one of these consistency criteria.
Asynchronous Distributed Systems, Atomic Consistency, Combination of consistency criteria, Linearizability, Message Passing, NP-Completeness, Shared Memory Abstraction, Sequential Consistency

C. Tutu, M. Raynal and M. Roy, "A Simple Protocol Offering Both Atomic Consistent Read Operations and Sequentially Consistent Read Operations," 19th International Conference on Advanced Information Networking and Applications (AINA'05) Volume 1 (AINA papers)(AINA), Taipei, Taiwan, 2005, pp. 961-966.
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