The context diagram and the activity diagram are not necessary, but help you visualize the use case and its position in the project.

环境图和活动图不是必须的，但是可以帮助你可视化用例和它在项目中的位置。

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Login has a longer term effect and carries some type of context, like a stateful activity.

登录则具有较长时间的效果，并附带某种类型的上下文，像一个有状态的活动。

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Capacity management is a vital activity in the context of cloud computing.

容量管理是云计算上下文中的重要活动。

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"In this context much activity including further detailed pre-construction engineering work will continue ahead of the later construction phase, " it said in a statement.

BBC: EDF cuts spending on planned Hinkley nuclear power plant

Donna Lieberman, executive director of the New York Civil Liberties Union, said it's "great news" that the city is on track to record the lowest homicide rate in decades and it's "especially good news" that it's happening in the context of reduced NYPD stop-and-frisk activity.

WSJ: Homicides Down for 2012

For one, international activity raises issues that do not arise in a single-country context.

FORBES: International Business Strategy: A Journey Of Its Own