XML Namespaces - The 'xmlns' Attribute

When using prefixes in XML, also-called namespace for the prefix must be defined.The namespace is defined by the xmlns attribute in the start tag of an element.
 

The namespace declaration has the following syntax. xmlns:prefix="URI".
 

<root>

<x:book xmlns:x="http://www.tibco.com/abc/dfg/">
  <x:index>
    <x:chapter>second</x:chapter>
    <x:page>thirty</x:page>
  </x:index>
</x:book>
 <y:book xmlns:y="http://www.tibcoworldin.com/test">
  <y:author>African Coffee Table</y:author>
  <y:price>90</y:price>
  <y:publisher>INX</y:publisher>
</y:book>
</root>

In the example above, the xmlns attribute in the <book> tag give the x: and y: prefixes a qualified namespace.

Default Namespaces

Defining a default namespace for an element saves us from using prefixes in all the child elements.
It has the following syntax:
 

xmlns="namespaceURI"

This XML carries HTML book information:

<book xmlns="http://www.tibco.com/abc/dfg/">
  <index>
    <chapter>second</chapter>
    <page>thirty</page>
  </index>
</book>

This XML carries information about a Book (price details):

<book xmlns ="http://www.tibcoworldin.com/test>
  <author>African Coffee Table</author>
  <price>90</price>
  <publisher>INX</publisher>
</book>