Core Java™ 2 Volume II - Advanced Features, Seventh Edition

Using Namespaces

Java uses packages to avoid name clashes. Programmers can use the same name for different classes as long as they aren't in the same package. XML has a similar namespace mechanism for element and attribute names.

A namespace is identified by a Uniform Resource Identifier (URI), such as

http://www.w3.org/2001/XMLSchema
uuid:1c759aed-b748-475c-ab68-10679700c4f2
urn:com:books-r-us

The HTTP URL form is the most common. Note that the URL is just used as an identifier string, not as a locator for a document. For example, the namespace identifiers

http://www.horstmann.com/corejava
http://www.horstmann.com/corejava/index.html

denote different namespaces, even though a web server would serve the same document for both URLs.

There ...