An event subscription contains a filter, which is a Boolean expression that evaluates to true for events it subscribes to and to false for all other events.

事件订阅包含筛选器，这是一个布尔表达式，对所订阅的事件求值为True，对其他所有事件求值为False。

youdao

The event selector string should be a valid XPath expression that is used by the CEI server to match events.

事件选择器字符串应当是有效的XPath表达，CEI服务器利用它来匹配事件。

youdao

“Water over the dam” is another expression about a past event.

Water over the dam（既成事实）是一个有关过去事件的表达。

youdao

Water over the dam is an expression about a past event.

VOA: special.2009.05.10

Clinton's comments at a joint press event with the Uruguayan leader were the highest-level expression of U.S.concern thus far about a Venezuelan arms buildup that gained momentum with an announcement this week that the South American state will buy Russian battle tanks and anti-aircraft missiles.

VOA: standard.2009.09.15

More than a social event, the carnival is an expression of belonging to a city, a social group and a nation.

UNESCO: Culture

For those of you who are unfamiliar with the term, it derives from an expression that was popular amongst medieval Londoners that referred to an event whose occurrence was believed to be impossible.

FORBES: Bevy of Black Swans Or Just A Flock of Seagulls?

Panelists at the event centered their main discussion points on the issues and challenges pertaining to freedom of expression and press freedom in Pakistan.

UNESCO: COMMUNICATION & INFORMATION