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In queueing theory, a discipline within the mathematical theory of probability, quasireversibility (sometimes QR) is a property of some queues. The concept was first identified by Richard R. Muntz and further developed by Frank Kelly. Quasireversibility differs from reversibility in that a stronger condition is imposed on arrival rates and a weaker condition is applied on probability fluxes. For example, an M/M/1 queue with state-dependent arrival rates and state-dependent service times is reversible, but not quasireversible. A network of queues, such that each individual queue when considered in isolation is quasireversible, always has a product form stationary distribution.〔Kelly, F.P. (1982). (Networks of quasireversible nodes ). In ''Applied Probability and Computer Science: The Interface'' (Ralph L. Disney and Teunis J. Ott, editors.) 1 3-29. Birkhäuser, Boston〕 Quasireversibility had been conjectured to be a necessary condition for a product form solution in a queueing network, but this was shown not to be the case. Chao et al. exhibited a product form network where quasireversibility was not satisfied. ==Definition== A queue with stationary distribution is quasireversible if its state at time ''t'', ''x(t)'' is independent of * the arrival times for each class of customer subsequent to time ''t'', * the departure times for each class of customer prior to time ''t'' for all classes of customer.〔Kelly, F.P., (Reversibility and Stochastic Networks ), 1978 pages 66-67〕 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「Quasireversibility」の詳細全文を読む スポンサード リンク
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