如前面所述，表达式节点还支持简单的算术和逻辑表达式。
As mentioned, expression nodes also support simple arithmetic and logical expressions.
公式节点中的运算符和语法同样适用与表达式节点。
The same operators and syntax of the Formula Node apply to the Expression Node.
表达式节点支持包含算术和布尔(真或假逻辑)运算符的简单表达式。
Expression nodes support simple expressions involving arithmetic and Boolean (true or false logic) operators.
使用表达式节点，你能够在单变量计算中输入单行的公式（表达式）。 表达式节点使用与公式节点相同的语法约定。
With the Expression Node, you can enter a single formula (expression) having one variable. The Expression Node uses the same syntax as the Formula Node.
标记将收集与查询表达式匹配的所有节点。
The tag will collect all nodes that match the query expression.
更聪明的方法是编写更具体的表达式，显式指定查找节点的位置。
It is wise to write more specific expressions that explicitly specify where to look for nodes.
在路径表达式的每个轴步骤中，节点测试出现在轴和谓词(用于进行任意筛选)之间。
In each axis step of a path expression, the node test comes between the axis and any predicates that might be present for arbitrary filtering.
可以很容易地将模板的动态内容部分替换为使用查询表达式指定正确模型节点的相应 、或标记。
The dynamic content sections of the template are easily replaced by the appropriate , or tags that use query expressions to target the correct model nodes.
这个表达式现在返回两个文本节点：12和 4.95。
有时候，比如计算的表达式返回一个节点集或者一个节点，这可能造成很大的混乱。
Sometimes -- such as when you're evaluating an expression that returns a set of nodes, or even a single node -- this can create a big mess.
我们说查询表达式产生一组节点，在这里导航结束。
We say that the query expression results in the set of nodes at which the navigation ends.
然后，计算表达式，得到的值将替换目标节点中的现有值。
The expression is then computed and the resulting value replaces the existing value in the target node.
然后计算表达式，得到的值将替换目标节点中的现有值。
The expression is then computed, and the resulting value replaces the existing value in the target node.
点号(.)在这里称为上下文项表达式，可以是节点或者原子值，视处理的序列中的当前项而定。
The dot (.) is now known as the context item expression, and might be a node or an atomic value, depending on the current item in the sequence being processed.
表达式中的问号(？)将由目标节点的现有文本值替换。
The question marks (?) in the expression are replaced with the existing text value of the target node.
最常见的操作之一是处理表达式返回的节点集。
One of the more common operations is to work with a set of nodes returned from an expression.
谓词是用于已有节点集的部分表达式。
A predicate is a partial expression that can be applied to an existing node set.
这（在表达式表示节点集的情况下）允许递增检索节点，而不是立即检索所有节点。
This (in the case of expressions representing node sets) allows the nodes to be retrieved incrementally, rather than all at once.
清单10使用一个SELECT查询来解析一个外部XML文档，并对结果应用一个XPath表达式来选取节点的特定子集。
Listing 10 USES a select query to parse an external XML document and apply an XPath expression to the result to select a specific subset of nodes.
查询表达式通过构建节点集合序列来处理
The query expression is processed by building a sequence of node collections
使用XPath表达式，可以选择合适的节点。
Using an XPath expression, you can select the appropriate nodes.
rename表达式用来对节点进行重命名。
定义输出结果集，使之包括一个integer类型的id列，它由XQuery表达式中指定的节点派生而来。
Define the output result set to include an ID column of type integer that is derived from the node specified in the XQuery expression.
这个XPath表达式的上下文节点是模板替换的元素，在这里是ATOM元素。
The context node for this XPath expression is the element that the template is replacing — in this case, an ATOM element.
考虑到使用一个XPath表达式可以选择多个节点，事情就更有趣了。
When you realize that you can select multiple nodes with a single XPath expression, things can get interesting.
所有相对XPath表达式都从这个当前节点开始进行计算。
All relative XPath expressions are evaluated starting from this current node.
一个上下文项，它是一个XPath表达式，指向作为列表达式的起点的节点(即accountingcustomerparty)。
A context item, which is an XPath expression used to point to a node that will be the starting point for the column expressions, namely AccountingCustomerParty.
replace表达式用来更新特定节点的特定值。
The replace expression is used to update a particular value of a particular node.
如果表达式为true，节点就添加到结果中。
If the expression is true, the node is added to the results.
delete表达式用来从XML文档删除特定节点。
The delete expression is used to delete a particular node from the XML document.
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