该函数解析文档，然后返回节点集。
for：使用for遍历节点集。
For: You can use for to take a node set and iterate over it.
使用扩展函数(节点集除外)。
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.
当然，节点集就是这类事物的任意组合。
And, of course, through a set of nodes it can be any combination of these things.
这是因为索引器只对特定的节点集感兴趣。
This is because the indexer is only interested in a specific set of nodes.
要记住，谓词作用于谓词本身左侧的节点集。
Remember, a predicate applies to the node set to the left of the predicate itself.
谓词可用于任何节点集
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.
结果元素集称为节点集。
当需要访问特定的元素、属性或节点集时它们很有用。
They can really help out when you want a particular element, attribute, or node set.
lowest 将返回内容中拥有最低数值的节点集。
math:lowest returns the node set whose content has the lowest numerical value.
最后，您可以将字符串和节点集的组合作为参数来传递。
Finally, you can pass a combination of a string and a node-set as parameters.
第1部分中提到，XPath选择总是返回一个节点集。
Remember from Part 1 that XPath selections always result in a set of nodes being returned.
XPath 2.0中不再有节点集，只有节点序列。
There are no more node-sets in XPath 2.0, just sequences of nodes.
并且该属性是关于已经选择的节点集的(即所有cd元素)。
And that attribute is assumed to be relative to the set of nodes already chosen (in this case, all the CD elements).
谓词必须作用于节点集，但是可作用于任何节点集。
A predicate must be applied to a node set, but it can be applied to any node set.
多数XPath表达式，特别是位置路径，都返回节点集。
Most XPath expressions, especially location paths, return node-sets.
您可以为可能出现在您的查询中的特定节点集指定附加的范围索引。
You can specify additional range indexes for particular node-sets that are likely to occur in your queries.
在很多方面，for就将节点集的当前值赋给变量从而操作该变量。
In many ways, for is the assignment of a variable to the current value in a node set, so you can operate on that variable.
当第三次使用内包节点集时，将在扩展存储它，以内存换取处理时间。
When an intensional node-set is used for the third time, it is stored extensionally, trading memory for processing time.
BC模式允许进行某些自动类型转换和自动选择节点集的第一个成员。
BC mode allows certain automatic type conversions to occur, as well as automatic selection of the first member of a node-set.
firstpos和lastpos是给定堆栈配置中xml节点集。
Firstpos and lastpos are the set of XML nodes in a given stack configuration.
只要已经按文档顺序排序了这两个操作数，就不必为中间节点集分配内存。
So long as the operands are both already sorted into document order, this avoids the need to allocate memory for the intermediate node sets.
Sets：Firefox 3.0实现了一些使用节点集的有用扩展。
Sets: Firefox 3.0 implements some useful extensions for working with node sets.
这种情况下，在打算使用字符串时却使用节点集，这通常导致调试非常困难。
In this case, a node set is used when a string is intended, usually with results that are hard to debug.
很容易忘记根元素，如果您确实忘记了，那么XPath会返回空的节点集。
It's easy to forget the root, but if you do, the XPath returns an empty node-set.
plete函数调用的结果是Statement元素的一个节点集。
The result of the rdf.complete function call is a node set of Statement elements.
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.
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。
XPath provides the expression language necessary to locate and retrieve individual nodes or node collections from the HTML document tree.
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