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XML DOM Tutorial

How to access, manipulate, and traverse XML documents using the Document Object Model (DOM) with code examples and key advantages like language independence and dynamic node editing.

DOM stands for Document Object Model and XML DOM defines a standard way to access and manipulate XML documents.

What is the DOM?

According to W3C documentation:

The W3C Document Object Model (DOM) is a platform and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure, and style of a document.

So, we can say that HTML DOM and XML DOM are similar. In facts, both defines a standard way to access and manipulate documents through a tree structure.

Example of HTML DOM

All HTML elements can be accessed through the HTML DOM.

For example

<!DOCTYPE html>
<html>
	<body>
		<h1 id="changeme">a H1 Heading</h1>
		<button type="button" onclick="document.getElementById('changeme').innerHTML='Hello World!'">Click!
		</button>
	</body>
</html>

Example of XML DOM

All XML elements can be accessed through the XML DOM.

<?xml version="1.0" encoding="UTF-8"?>
<people>
	<book category="children">
		<title lang="en">Harry Potter</title>
		<author>J K. Rowling</author>
		<year>2005</year>
		<price>29.99</price>
	</book>
</people>

This code retrieves the text value of the first <author> element in an XML document:

txt = xmlDoc.getElementsByTagName("author")[0].childNodes[0].nodeValue;

XML, DOM and XML DOM

DOM defines the objects and properties and methods (interface) to access all XML elements. It is separated into 3 different parts

  • Core DOM: standard model for any structured document.
  • XML DOM: standard model for XML documents.
  • HTML DOM: standard model for HTML documents.

XML DOM is a standard object model for XML.

XML documents have a hierarchy of informational units called nodes while DOM is a standard programming interface of describing those nodes and the relationships between them.

XML DOM also provides an API that allows a developer to add, edit, move or remove nodes anywhere in the tree to create an application.

Advantages of XML DOM

The following are the advantages of XML DOM.

  • XML DOM is language and platform independent.
  • XML DOM is traversable. Information in XML DOM is organized in a hierarchy which allows developer to navigate around the hierarchy looking for specific information.
  • XML DOM is modifiable - It is dynamic in nature providing the developer a scope to add, edit, move or remove nodes at any point on the tree.

Disadvantages of XML DOM

  • It consumes more memory (if the XML structure is large) as program written once remains in memory all the time until and unless removed explicitly.
  • Due to the extensive usage of memory, its operational speed, compared to SAX is slower.
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