XPath学习

In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document (root) nodes.
在XPath里，有7中不同的节点：元素，属性，文本，名称空间，处理指令，内容，文档（根目录root）节点。

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XPath Terminology
XPath术语

Nodes
节点

In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document (root) nodes. XML documents are treated as trees of nodes. The root of the tree is called the document node (or root node).
在XPath里，有7中不同的节点：元素，属性，文本，名称空间，处理指令，内容，文档（根）节点，XML文档是节点树状结构。“树根”称作文档节点（或根节点）。

Look at the following XML document:
下面给出一个XML文档：

<?xml version="1.0" encoding="ISO-8859-1"?>

<bookstore>

<book>
    <title lang="en">Harry Potter</title>

    <author>J K. Rowling</author> 
    <year>2005</year>
    <price>29.99</price>
</book>

</bookstore>

Example of nodes in the XML document above:
上述XML文档中的节点实例：

<bookstore>    (document node)

<author>J K. Rowling</author>    (element node)

lang="en"    (attribute node)

Atomic values
“单元素（Atomic）”属性值

Atomic values are nodes with no children or parent.
“单元素”属性值只没有子节点和父节点。

Example of atomic values:
“单元素（Atomic）”属性值例子：

J K. Rowling

"en"

Items
项目

Items are atomic values or nodes.
项目是指单元素或节点。

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Relationship of Nodes
节点间的关系

Parent
父类

Each element and attribute has one parent.
每个元素和属性都有一个“父类”。

In the following example; the book element is the parent of the title, author, year, and price:
在下面的例子里：book元素是title, author, year, 和 price元素的父元素。

<book>
    <title>Harry Potter</title>
    <author>J K. Rowling</author>

    <year>2005</year>
    <price>29.99</price>
</book>

Children
子类

Element nodes may have zero, one or more children.
节点元素可拥有任意个数的子类。

In the following example; the title, author, year, and price elements are all children of the book element:
在下面例子里，title, author, year, 和 price元素都是book元素的子元素。

<book>
    <title>Harry Potter</title>

    <author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
</book>

Siblings
同属类

Nodes that have the same parent.
拥有相同的父类的节点称之为同属类。

In the following example; the title, author, year, and price elements are all siblings:
在下面的例子里title, author, year, 和price元素都是“同属类元素”。

<book>
    <title>Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>

    <price>29.99</price>
</book>

Ancestors
祖类

A node's parent, parent's parent, etc.
一个节点的父类，父类的父类及更多称为该节点的祖类。

In the following example; the ancestors of the title element are the book element and the bookstore element:
在下面例子里，title元素的“祖类元素”是book元素和bookstore元素。

<bookstore>

<book>
    <title>Harry Potter</title>

    <author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
</book>

</bookstore>

Descendants
下属类

A node's children, children's children, etc.
节点的子类，子类的子类及更多称为下属类。

In the following example; descendants of the bookstore element are the book, title, author, year, and price elements:
在下面的例子里，bookstore元素的下属类元素是book, title, author, year, 和price元素：

<bookstore>

<book>
    <title>Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>

    <price>29.99</price>
</book>

</bookstore>