Given a set of users and items, CF applications provide recommendations to the current user of the system. Four ways of generating recommendations are typical.

CF应用程序根据用户和项目历史向系统的当前用户提供推荐。

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The post shows the four key habits for maintaining a comprehensive system for all your information and tasks, as well as my current setup.

为你所有的信息和任务建立综合系统，需要4个关键习惯，我现在也是这么做的。

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The current addressing system—called IPv4—has about four billion possible addresses.

现在的寻址系统称为IPv4，它拥有40亿个有效地址。

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Another recommendation calls for all politicians to serve four-year terms, to replace the current system under which senators serve for six years or three years and deputies and constables serve for three years.

BBC: Jersey Electoral Commission recommends smaller States

The teams ranked one to four in the current world rankings were kept apart by the seeding system, with the next four teams - those ranked fifth to eighth - the second names into each pool.

BBC: England meet Scots in World Cup

By and large, businesses welcomed this tidying up, even though they will pay more tax during a four-year transition to a new system of payment, under which big firms will pay tax quarterly on a current-year basis, rather than in arrears as now.

ECONOMIST: Gordon Brown’s progress | The