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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Expected marginal seat revenue ： ウィキペディア英語版 Expected marginal seat revenue EMSR stands for Expected Marginal Seat Revenue and is a very popular heuristic in Revenue Management. There are two versions: EMSRa〔Belobaba, P. P., Air Travel Demand and Airline Seat Inventory Management. Flight Transportation Laboratory. Cambridge, MIT. PhD, 1987〕 and EMSRb,〔Belobaba, P. P., Optimal vs. heuristic methods for nested seat allocation. Presentation at ORSA/TIMS Joint National Meeting, 1992〕 both of which were introduced by Belobaba. Both methods are for ''n''-class, static, single-resource problems. Because the models are static some assumptions apply: classes are indexed in such a way that the fare for the highest class, $r\_$, is higher than the fare for the next highest class, $r\_$, so $r\_$ > $r\_$ > ... > $r\_$; demand arrives in a strict low to high order in stages that are indexed with ''j'' as well; demand for class ''j'' is distributed with cdf $F\_j(x)$. For simplicity it is also assumed that demand, capacity and the distributions are continuous, although it is not very difficult to drop this assumption. ==EMSRa== EMSRa is the first version that Belobaba came up with. The idea behind the heuristic is to add the protection limits that are calculated by applying Littlewood's rule to successive classes. Suppose that we are in stage ''j+1'' and we want to calculate how much capacity we need to protect for stages ''j, j-1,..., 1''. Then we are actually calculating protection limit $y$j. To do so we consider every class in ''j, j-1,..., 1'' and compare that class, indexed with ''k'', with ''j+1'' in isolation. For every combination of ''k'' and ''j+1'' we compute the protection level for that class with Littlewood's rule: :$P\; (\; D\_k\; >\; y\_k^)\; =\; \backslash frac$ The idea of EMSRa then is to add all these protection limits to get the protection limit for $y\_j$. :$y\_j\; =\; \backslash sum\_^j\; y\_k^$ However, there is a problem with this method because it does not take the statistical averaging effect into account. Suppose, for example, that classes ''1'' to ''j'' have the same fare ''r'', then EMSRa will calculate the protection limit for $y\_$ with :$P(\; D\_k\; >\; y\_k^)\; =\; \backslash frac$ However, because the fare for all these classes is the same they should be aggregated. EMSRa will calculate protection limits that are too conservative. In other words, it will reserve too many seats for the higher fares, thereby rejecting too many low fare bookings. Although having equal fares is not realistic this will also happen if the difference between fares is small. Therefore EMSRb was invented. 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「Expected marginal seat revenue」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.