XML中的根节点是什么？

Question

我当时正在读一本电子书，它有以下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，当我继续阅读剩下的部分时，我认为我误解了什么是根元素。据我所知，根节点是<sonnet>节点。

但在书中我发现下面这个

与其他节点不同，根节点没有父节点。它总是至少有一个子元素，即document元素。根节点还包含文档元素之外的注释或处理指令。在我们的示例文档中，名为xml样式表和cocoon的两个处理指令都是根节点的子节点，在标记之前出现的注释和标记后面出现的注释也是如此。

根据这一点，整个文档被认为是根。如果是，那又是什么呢？显然，处理指令和注释不是节点的子节点。

我能理解吗？

UPdate

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

这里的根元素是什么？不是吃的吗？

Answer 1

根节点没有视觉显示或文本表示。它是一个概念节点，包含文档中的其他所有内容。在您的文档示例中，如下所示：

/ (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()

如下图所示，示例中的根节点有两个处理指令、四个注释和一个子元素。

这个单个子元素(十四行诗)就是所谓的“文档元素”。它有时也被称为“根元素”，但许多人喜欢避免使用这个术语，以尽量减少与“根节点”的混淆，因为它们是完全独立的。