策略表达式窗口应当如图7 所示。
这些策略断言自身可以包含策略表达式。
These policy assertions can themselves contain policy expressions.
标准形式策略表达式是冗长的，特别是如果它包含嵌套替代项。
The normal-form expression of a policy can be lengthy, especially if it involves nested alternatives.
除了简化元素嵌入，紧凑表达式也提供一种引用和重用策略表达式的方法。
Besides simplifying element nesting, compact expression also provides a way to reference and reuse policy expressions.
策略表达式既允许使用简单的声明性断言，也允许使用更为复杂的条件断言。
Policy expressions allow for both simple declarative assertions as well as more sophisticated conditional assertions.
在一个标准形式策略表达式中，所有这些嵌套的策略断言必须是标准形式。
In a normal-form policy expression, all these nested policy assertions must themselves also be in normal form.
实际上，策略表达式只是使用一个尖括号格式的逻辑表达式，断言是子句。
Policy expressions really are just logic expressions using a pointy-bracket format, with assertions as clauses.
策略引用可用于本地策略表达式，如清单3所示，也可用于外部策略表达式。
Policy references can be used both for local policy expressions, as shown in Listing 3, and for external policy expressions.
实际上，策略表达式只是使用一个尖括号格式的逻辑表达式，断言是子句。
Policy expressions really are just logic expressions using a pointy - bracket format, with assertions as clauses.
对于外部策略表达式，引用的UR i属性通常提供外部策略的真实url。
For external policy expressions, the reference's URI attribute normally gives the actual URL of the external policy.
在本系列之前的文章中，您可能见过WS - SecurityPolicy断言包含嵌套的策略表达式。
You've seen this in past articles of this series, where many of the WS-SecurityPolicy assertions contain nested policy expressions.
WS - Policy定义了一些选项，您可以用来创建比标准形式更简明的策略表达式，使策略更易理解。
WS-Policy defines options you can use to create policy expressions that are more concise than the normal form permits, making the policies easier for humans to understand.
为了方便起见，WS - Policy定义了一个标准形式的策略表达式和一组可以创建更紧凑的策略表达式的规则。
For convenience, WS-Policy defines both a normal-form expression of a policy and a set of rules you can use to create more-compact policy expressions.
WS - Policy定义了一个变换集，您可以用来将使用紧凑选项的策略表达式转换成标准形式，因此没有理由直接使用标准形式。
WS-Policy defines a set of transformations you can apply to convert policy expressions using the compact options into normal form, so there's little reason to use normal form directly.
WS - Policy定义了一个变换集，您可以用来将使用紧凑选项的策略表达式转换成标准形式，因此没有理由直接使用标准形式。
WS-Policy defines a set of transformations you can apply to convert policy expressions using the compact options into normal form, so there's little reason to use normal form directly.
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