A method for identifying XML elements and attributes that have the same name, but different meanings. For example, ADDRESS is a tag that can be used to identify totally different data elements such as "street address" and "IP address."

An XML Namespace is a Prefix
An XML namespace uses a URL as a prefix in front of the "local name." The combination of URL and local name makes the element or attribute name unique. The URL is used only as a way to create a unique prefix and does not have to resolve to a real page on the Internet. However, a document may be stored where the URL points that provides information about the namespace (see RDDL).