例如，可以配置一个Message Filter中介原语，以根据某个特定XPath表达式的值(是否为真)来按多种路径之一传递消息。

For example, you can configure a message Filter mediation primitive to route messages down one of multiple paths, depending on whether a particular XPath expression holds true.

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和大多数语言一样，Scala的if测试一个条件表达式，然后根据结果为真或假来跳转到响应语句块中。

As in most every language, Scala's if evaluates a conditional expression, then proceeds to a block if the result is true or branches to an alternate block if the result is false. A simple example.

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断言表示为一些布尔表达式，程序员相信在程序中的某个特定点该表达式的值为真。

Assertions represent Boolean expressions that the programmer believes to be true at specific points in the program.

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