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XML Tutorial

XML HOME XML Introduction XML How to use XML Tree XML Syntax XML Elements XML Attributes XML Namespaces XML Display XML HttpRequest XML Parser XML DOM XML XPath XML XSLT XML XQuery XML XLink XML Validator XML DTD XML Schema XML Server XML Examples XML Quiz XML Certificate

XML AJAX

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XML DOM

DOM Introduction DOM Nodes DOM Accessing DOM Node Info DOM Node List DOM Traversing DOM Navigating DOM Get Values DOM Change Nodes DOM Remove Nodes DOM Replace Nodes DOM Create Nodes DOM Add Nodes DOM Clone Nodes DOM Examples

XPath Tutorial

XPath Introduction XPath Nodes XPath Syntax XPath Axes XPath Operators XPath Examples

XSLT Tutorial

XSLT Introduction XSL Languages XSLT Transform XSLT <template> XSLT <value-of> XSLT <for-each> XSLT <sort> XSLT <if> XSLT <choose> XSLT Apply XSLT on the Client XSLT on the Server XSLT Edit XML XSLT Examples

XQuery Tutorial

XQuery Introduction XQuery Example XQuery FLWOR XQuery HTML XQuery Terms XQuery Syntax XQuery Add XQuery Select XQuery Functions

XML DTD

DTD Introduction DTD Building Blocks DTD Elements DTD Attributes DTD Elements vs Attr DTD Entities DTD Examples

XSD Schema

XSD Introduction XSD How To XSD <schema> XSD Elements XSD Attributes XSD Restrictions

XSD Complex

XSD Elements XSD Empty XSD Elements Only XSD Text Only XSD Mixed XSD Indicators XSD <any> XSD <anyAttribute> XSD Substitution XSD Example

XSD Data

XSD String XSD Date XSD Numeric XSD Misc XSD Reference

Web Services

XML Services XML WSDL XML SOAP XML RDF XML RSS

References

DOM Node Types DOM Node DOM NodeList DOM NamedNodeMap DOM Document DOM Element DOM Attribute DOM Text DOM CDATA DOM Comment DOM XMLHttpRequest DOM Parser XSLT Elements XSLT/XPath Functions

XML DOM Nodes

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According to the XML DOM, everything in an XML document is a node:

  • The entire document is a document node
  • Every XML element is an element node
  • The text in the XML elements are text nodes
  • Every attribute is an attribute node
  • Comments are comment nodes

DOM Example

Look at the following XML file (books.xml):

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Header

<?xml version="1.0" encoding="UTF-8"?>
<bookstore>
  <book category="cooking">
    <title lang="en">Everyday Italian</title>
    <author>Giada De Laurentiis</author>
    <year>2005</year>
    <price>30.00</price>
  </book>
  <book category="children">
    <title lang="en">Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
  </book>
  <book category="web">
    <title lang="en">XQuery Kick Start</title>
    <author>James McGovern</author>
    <author>Per Bothner</author>
    <author>Kurt Cagle</author>
    <author>James Linn</author>
    <author>Vaidyanathan Nagarajan</author>
    <year>2003</year>
    <price>49.99</price>
  </book>
  <book category="web" cover="paperback">
    <title lang="en">Learning XML</title>
    <author>Erik T. Ray</author>
    <year>2003</year>
    <price>39.95</price>
  </book>
</bookstore>

The root node in the XML above is named <bookstore>.

All other nodes in the document are contained within <bookstore>.

The root node <bookstore> holds 4 <book> nodes.

The first <book> node holds the child nodes: <title>, <author>, <year>, and <price>.

The child nodes contain one text node each, "Everyday Italian", "Giada De Laurentiis", "2005", and "30.00".

Text is Always Stored in Text Nodes

A common error in DOM processing is to expect an element node to contain text.

However, the text of an element node is stored in a text node.

In this example: <year>2005</year>, the element node <year> holds a text node with the value "2005".

"2005" is not the value of the <year> element!

The XML DOM Node Tree

The XML DOM views an XML document as a tree-structure. The tree structure is called a node-tree.

All nodes can be accessed through the tree. Their contents can be modified or deleted, and new elements can be created.

The node tree shows the set of nodes, and the connections between them. The tree starts at the root node and branches out to the text nodes at the lowest level of the tree:

DOM node tree

The image above represents the XML file books.xml.

Node Parents, Children, and Siblings

The nodes in the node tree have a hierarchical relationship to each other.

The terms parent, child, and sibling are used to describe the relationships. Parent nodes have children. Children on the same level are called siblings (brothers or sisters).

  • In a node tree, the top node is called the root
  • Every node, except the root, has exactly one parent node
  • A node can have any number of children
  • A leaf is a node with no children
  • Siblings are nodes with the same parent

The following image illustrates a part of the node tree and the relationship between the nodes:

Node tree

Because the XML data is structured in a tree form, it can be traversed without knowing the exact structure of the tree and without knowing the type of data contained within.

You will learn more about traversing the node tree in a later chapter of this tutorial.

First Child - Last Child

Look at the following XML fragment:

<bookstore>
  <book category="cooking">
    <title lang="en">Everyday Italian</title>
    <author>Giada De Laurentiis</author>
    <year>2005</year>
    <price>30.00</price>
  </book>
</bookstore>

In the XML above, the <title> element is the first child of the <book> element, and the <price> element is the last child of the <book> element.

Furthermore, the <book> element is the parent node of the <title>, <author>, <year>, and <price> elements.


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