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In theoretical computer science, the CAP theorem, also known as Brewer's theorem, states that it is impossible for a distributed computer system to simultaneously provide all three of the following guarantees:〔Seth Gilbert and Nancy Lynch, (“Brewer's conjecture and the feasibility of consistent, available, partition-tolerant web services” ), ''ACM SIGACT News'', Volume 33 Issue 2 (2002), pg. 51-59.〕〔("Brewer's CAP Theorem" ), julianbrowne.com, Retrieved 02-Mar-2010〕〔("Brewers CAP theorem on distributed systems" ), royans.net〕 *''Consistency'' (all nodes see the same data at the same time) *''Availability'' (a guarantee that every request receives a response about whether it succeeded or failed) *''Partition tolerance'' (the system continues to operate despite arbitrary partitioning due to network failures) In 2012 Brewer clarified some of his positions, including why the oft-used "two out of three" concept can be misleading or misapplied, and the different definition of consistency used in CAP relative to the one used in ACID.〔Eric Brewer, (“CAP twelve years later: How the "rules" have changed” ), ''IEEE Explore'', Volume 45, Issue 2 (2012), pg. 23-29.〕 == History == According to University of California, Berkeley computer scientist Eric Brewer, the theorem first appeared in autumn 1998.〔 It was published as the CAP principle in 1999〔Armando Fox and Eric Brewer, “Harvest, Yield and Scalable Tolerant Systems”, ''Proc. 7th Workshop Hot Topics in Operating Systems (HotOS 99)'', IEEE CS, 1999, pg. 174-178.〕 and presented as a conjecture by Brewer at the 2000 Symposium on Principles of Distributed Computing (PODC).〔Eric Brewer, ("Towards Robust Distributed Systems" )〕 In 2002, Seth Gilbert and Nancy Lynch of MIT published a formal proof of Brewer's conjecture, rendering it a theorem.〔 This last claim has been criticized however.〔Mark Burgess, ("Deconstructing the `CAP theorem' for CM and DevOps" )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「CAP theorem」の詳細全文を読む スポンサード リンク
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