XML in a Nutshell, 3rd Edition

Namespace Syntax

Namespaces distinguish between elements with different meanings but the same name by assigning each element a URI. Generally, all the elements from one XML application are assigned to one URI, and all the elements from a different XML application are assigned to a different URI. These URIs are called namespace names . Elements with the same name but different URIs are different kinds of elements. Elements with the same name and the same URI are the same kind of element. Most of the time a single XML application has a single namespace URI for all its elements, though a few applications use multiple namespaces to subdivide different parts of the application. For instance, XSL uses different namespaces for XSL Transformations (XSLT) and XSL Formatting Objects (XSL-FO).