0000000000599523
AUTHOR
Edel Sherratt
Distributed ASM - Pitfalls and solutions
Published version of a chapter in the book: Abstract State Machines, Alloy, B, TLA, VDM, and Z. Also available from the publisher at: http://dx.doi.org/10.1007/978-3-662-43652-3_18 While sequential Abstract State Machines (ASM) capture the essence of sequential computation, it is not clear that this is true of distributed ASM. This paper looks at two kinds of distributed process, one based on a global state and one based on variable access. Their commonalities are extracted and conclusions for the general understanding of distributed computation are drawn, providing integration between global state and variable access.
Eventual Consistency Formalized
Distribution of computation is well-known, and there are several frameworks, including some formal frameworks, that capture distributed computation. As yet, however, models of distributed computation are based on the idea that data is conceptually centralized. That is, they assume that data, even if it is distributed, is consistent. This assumption is not valid for many of the database systems in use today, where consistency is compromised to ensure availability and partition tolerance. Starting with an informal definition of eventual consistency, this paper explores several measures of inconsistency that quantify how far from consistency a system is. These measures capture key aspects of e…