例如，可以配置一个MessageFilter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.
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.
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.
为了配置Route节点来模拟floworder节点的行为，路由表达式求值必须始终为真。
In order to configure the Route node to mimic the behaviour of the FlowOrder node the routing expressions being evaluated must always resolve to true.
布尔表达式：一种值为真或假的表达式。
布尔表达式的设计意图就是表达运行时值为表达式时值意图真或假的属性，在某个时刻判断此属性的值就可以决定执时刻可以决定行是否继续。
Boolean expressions are intended precisely to express background contract express runtime true or false properties-properties that at any point in the execution may hold or not hold.
这些限定符使您能够指定，为使匹配为真，正则表达式的某个给定组件必须出现多少次。
These quantifiers let you specify how many times a given component of a regular expression must occur for a match to be true.
这些限定符使您能够指定，为使匹配为真，正则表达式的某个给定组件必须出现多少次。
These quantifiers let you specify how many times a given component of a regular expression must occur for a match to be true.
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