The same operators and syntax of the Formula Node apply to the Expression Node.
公式节点中的运算符和语法同样适用与表达式节点。
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.
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。
The input value can be a simple expression or be a value computed by another node.
该输入值可以是一个简单表达式，或者是由另一节点计算的一个值。
Since there are no steps following the variable name, this query expression results in a single node which happens to be the current node.
由于在变量名后面没有任何步骤，因此该查询表达式将产生一个单一节点，即正好是当前的节点。
It is here, though, that a common question is asked: How do you write the query expression to get the correct node from an arbitrarily complex DOM?
但是，这里经常有人提问这样一个问题：如何编写查询表达式才能从任何复杂的DOM中获取正确的节点？
Typically, the accessor factory uses a path expression to locate a particular document node or to create a node (or even a complete path of nodes) in the state document model.
通常，访问器工厂使用路径表达式来定位特定的文档节点，或在状态文档模型中创建阶段（甚至阶段的完整路径）。
Each tag has a node attribute that takes a query expression describing a single model node in the DOM.
每种标记都有一个节点属性，该属性携带一个描述DOM中单一模型节点的查询表达式。
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.
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。
If there are no steps in the query expression, the query expression results in the start node, pending any additional filtering.
如果查询表达式中没有任何步骤，则查询表达式将产生开始节点，挂起任何附加的筛选。
The expression is evaluated with respect to a certain context node, which in this case is the entire document.
表达式是针对特定的上下文节点计算的，在这个例子中是整个文档。
To start at any other node in the DOM, start the query expression with a variable name that will be associated with that node when the query expression is interpreted.
在DOM中的任何其他节点开始，使用一个变量名开始查询表达式，在解释查询表达式时，变量名将与该节点关联。
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.
然后计算表达式，得到的值将替换目标节点中的现有值。
When you use.. in an expression, it instructs the expression to work up one level from the current node in the hierarchy (again, similar to working with directories in UNIX operating systems).
当在表达式中使用. .时，它能指示表达式从层次结构中的当前节点上提一层(这亦类似于unix操作系统内目录的处理)。
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.
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 reason code "XUTY0008" shown in the error message quickly points you to the fact that "the target node of a replace expression is not a single node".
错误消息中显示的原因码 “XUTY0008” 表示 “替换表达式的目标节点不是单一节点”。
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.
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。
The question marks (?) in the expression are replaced with the existing text value of the target node.
表达式中的问号(？)将由目标节点的现有文本值替换。
Of course, you could use this returned Node as the context for a new XPath expression, as shown in Listing 12.
当然也可将返回的这个Node作为新xpath表达式的上下文，如清单12所示。
In itself, this isn't very useful, but what's important is that you can use DOM manipulation code on the Node returned from the XPath expression evaluation.
返回的结果本身没有多少用处，但关键是可以使用DOM对XPath表达式求值返回的Node进行操作。
An XPath expression allows you to define a set of node relationships in the document and return subsets of content from the document based on these relationships.
XPath表达式允许您在文档中定义一个节点关系集，并允许根据这些关系从文档返回内容的子集。
A variant of enforce, this check is more complex, as an additional context check is made based on the node returned from the XPath expression test.
是强制性的一种变形，这个检查更复杂一些，它基于节点XPath表达式的返回值额外执行一次环境检查。
The query expression is processed by building a sequence of node collections
查询表达式通过构建节点集合序列来处理
The rename expression is used to rename a node.
rename表达式用来对节点进行重命名。
Define the output result set to include an ID column of type integer that is derived from the node specified in the XQuery expression.
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。
XPath provides the expression language necessary to locate and retrieve individual nodes or node collections from the HTML document tree.
XPath提供从HTML文档树定位和检索单个节点或节点集所需的表达式语言。
The context node for this XPath expression is the element that the template is replacing — in this case, an ATOM element.
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 condition specified in the node can use an ESQL reference or XPath expression.
节点中指定的条件可以使用ESQL引用或XPath表达式。
The XPath expression must identify a portion of the XML data — that is, a specific XML node — that returns one data value.
（XPath表达式必须指定XML数据的一部分，即一个 XML节点，它必须返回一个数据值）。
The DatabaseRetrieve node can be used to modify a message using information that is obtained from a database by specifying an XPath expression in the processing node.
DatabaseRetrieve节点可用于修改消息，方法是使用从数据库中获得的信息并通过在处理节点中指定XPath表达式。
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