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