XML Document Object Model (DOM)

XML DOM

Prepared by: Pawan Dhawan
Software Engineer
Jan -30-2012
BOSS Webtech Private Limited
www.bosswebtech.com

Points we will covered

• What is XML DOM .
• Its structure.
• Its advantages and disadvantages
• Its uses.

WHAT IS DOM ?
• DOM is the Document Object Model.
• The DOM is a W3C (World Wide Web
Consortium) standard.
• The DOM defines a standard for accessing
documents like XML and HTML:
• DOM is memory-based, this making it
traversable and editable.
• DOM is not language-specific, nor is it
platform-specific.

What is the XML DOM?

The XML DOM is:
• A standard object model for XML
• A standard programming interface for XML
• Platform- and language-independent
• A W3C standard

DOM Nodes

According to the DOM, everything in an XML
document is a node.
The DOM says:
• 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
<?xml version="1.0" encoding="ISO-8859-1"?>
<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="web" cover="paperback">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore>

XML DOM Properties

These are some typical DOM properties:
• x.nodeName - the name of x
• x.nodeValue - the value of x
• x.parentNode - the parent node of x
• x.childNodes - the child nodes of x
• x.attributes - the attributes nodes of x

Note: In the list above, x is a node object.

XML DOM Methods

• x.getElementsByTagName(name) - get all
elements with a specified tag name
• x.appendChild(node) - insert a child node to x
• x.removeChild(node) - remove a child node
from x

Note: In the list above, x is a node object.

Example
txt=xmlDoc.getElementsByTagName("title")[0].c
hildNodes[0].nodeValue
• xmlDoc - the XML DOM object .
• getElementsByTagName("title")[0] - the first
<title> element
• childNodes[0] - the first child of the <title>
element (the text node)
• nodeValue - the value of the node (the text
itself)

Traversing the Node Tree
<html>
<head>
<script type="text/javascript" src="loadxmlstring.js"></script>
</head>
<body>
<script type="text/javascript">
text="<book>";
text=text+"<title>Everyday Italian</title>";
text=text+"<author>Giada De Laurentiis</author>";
text=text+"<year>2005</year>";
text=text+"</book>";
xmlDoc=loadXMLString(text);
// documentElement always represents the root node
x=xmlDoc.documentElement.childNodes;
for (i=0;i<x.length;i++)
{
document.write(x[i].nodeName);
document.write(": ");
document.write(x[i].childNodes[0].nodeValue);
document.write("<br />");
}
</script>
</body>
</html>

Out Put
title: Everyday Italian
author: Giada De Laurentiis
year: 2005

Advantages of XML DOM
• XML structure is traversable.
Each node can be randomly accessed (one or
more times) by traversing the tree.
• XML structure is modifiable.
Since the XML structure is resident in memory,
values can be added, changed, and removed.
• The DOM standard is maintained by the World
Wide Web Consortium.

Disadvantages of XML DOM
• Resource intensive
Since the XML structure is resident in memory,
the larger the XML structure is, the more
memory it will consume.
• Relative speed
In comparison to SAX, DOM can be much
slower due to its resource usage/ needs.

Uses of XML DOM
• The XML DOM defines a standard way for
accessing and manipulating XML documents.
• The DOM presents an XML document as a
tree-structure.
• Knowing the XML DOM makes working easier
with XML.

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XML Document Object Model (DOM)

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