什么是XML中的根节点？

Question

我在读电子书，它有以下的XML代码。

<?xml version="1.0"?> 
<?xml-stylesheet href="sonnet.xsl" type="text/xsl"?> 
<?cocoon-process type="xslt"?> 
<!DOCTYPE sonnet [ 
    <!ELEMENT sonnet (auth:author, title, lines)> 
    <!ATTLIST sonnet public-domain CDATA "yes" 
     type (Shakespearean | Petrarchan) "Shakespearean"> 
    <!ELEMENT auth:author (last-name,first-name,nationality, 
     year-of-birth?,year-of-death?)> 
    <!ELEMENT last-name (#PCDATA)> 
    <!ELEMENT first-name (#PCDATA)> 
    <!ELEMENT nationality (#PCDATA)> 
    <!ELEMENT year-of-birth (#PCDATA)> 
    <!ELEMENT year-of-death (#PCDATA)> 
    <!ELEMENT title (#PCDATA)> 
    <!ELEMENT lines (line,line,line,line, 
     line,line,line,line,line,line,line, 
     line,line,line)> 
    <!ELEMENT line (#PCDATA)> 
]> 
<!-- Default sonnet type is Shakespearean, the other allowable --> 
<!-- type is "Petrarchan." --> 
<sonnet type="Shakespearean"> 
    <auth:author xmlns:auth="http://www.authors.com/"> 
    <last-name>Shakespeare</last-name> 
    <first-name>William</first-name> 
    <nationality>British</nationality> 
    <year-of-birth>1564</year-of-birth> 
    <year-of-death>1616</year-of-death> 
    </auth:author> 
    <!-- Is there an official title for this sonnet? They're 
    sometimes named after the first line. --> 
    <title>Sonnet 130</title> 
    <lines> 
    <line>My mistress' eyes are nothing like the sun,</line> 
    <line>Coral is far more red than her lips red.</line> 
    <line>If snow be white, why then her breasts are dun,</line> 
    <line>If hairs be wires, black wires grow on her head.</line> 
    <line>I have seen roses damasked, red and white,</line> 
    <line>But no such roses see I in her cheeks.</line> 
    <line>And in some perfumes is there more delight</line> 
    <line>Than in the breath that from my mistress reeks.</line> 
    <line>I love to hear her speak, yet well I know</line> 
    <line>That music hath a far more pleasing sound.</line> 
    <line>I grant I never saw a goddess go,</line> 
    <line>My mistress when she walks, treads on the ground.</line> 
    <line>And yet, by Heaven, I think my love as rare</line> 
    <line>As any she belied with false compare.</line> 
    </lines> 
</sonnet> 
<!-- The title of Sting's 1987 album "Nothing like the sun" is --> 
<!-- from line 1 of this sonnet. 

问题是当我继续阅读的其余部分时，我想我误解了什么是根元素。据我所知，根节点为<sonnet>节点。

但在本书中，我发现旁边这个

不像其他的节点，根节点没有父。它始终在 至少有一个孩子，文档元素。根节点还包含 注释或处理指令，它们位于文档 元素之外。在我们的样本文档中，这两个处理指令命名 xmlstylesheet和茧过程是根节点的两个孩子， 的是，标签和标签后出现的 评论之前出现的注释。

accordning到整个文件被认为是根。如果是这样的话？很明显，处理指令和注释不是节点的子节点。

我minunderstand？

更新

<?xml version="1.0"?> 
<Food> 
    <Cateogry> Vegetable</Cateogry> 
    <Cateogry> Fruits</Cateogry> 
    <Cateogry> other</Cateogry> 
</Food> 

什么是这里的根元素？它不是食物吗？

Answer 1

根节点没有视觉表现或文本表示。它是一个包含文档中其他所有内容的概念节点。在文档的示例中，这将是这样的：

/ (root node) 
    |-- processing-instruction() xml-stylesheet 
    |-- processing-instruction() cocoon-process 
    |-- comment() 
    |-- comment() 
    |-- sonnet (document element) 
     |-- auth:author 
      |-- last-name 
      |-- .... 
     |-- comment() 
     |-- title 
     |-- lines 
      |-- line 
      |-- line 
      |-- .... 
    |-- comment() 
    |-- comment() 

如这里所示，在你的例子根节点2个处理指令，4个注释和1种元素作为孩子。

这种单一的子元素（十四行诗）是所谓的“文档元素”。它有时也被称为“根元素”，但很多人喜欢避免这个词，以最大限度地减少与“根节点”的混淆，因为它们是两个完全分离的东西。