Requirement: This value is required to be unique among document flows for Web Service protocol.

要求：在Web服务协议的文档流中该值必须是唯一的。

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Additionally, a usage of the requirement can also be set as required, optional, or prohibited through the use attribute (the default value is required).

此外，需求的使用还可以通过use属性设置为required, optional或prohibited(默认值为required)。

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As at date measures are a specialised variant of a normal measure which are calculated for a given date and can be used whenever a measure value is required for a particular date in the calendar only.

As at Date度量是常规度量的一种特殊变体，针对给定日期加以计算，且每当日历中的一个特定日期需要一个度量值时，都会用到它。

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That's what is pushing up the value of its landing slots, so airlines are required to maximise profit from each slot, and that is best done by long-haul routes.

BBC: BA: long-haul and the short of it

Barbero says technology is only part of the answer: troops have to be trained to get the full value of counter-IED technology, and detailed intelligence is required to attack enemy networks and finances.

FORBES: Move up http://i.forbesimg.com t Move down

If the marginal value that a customer receives for increased reliability is less than the marginal cost required to increase reliability for that customer, then a systemwide relocation of lines would likely lead to wasted resources.

WSJ: Should Utilities Be Required to Bury Power Lines to Protect Them?