Essential XML: Beyond Markup

Names

Both elements and attributes are named. To ensure that names can be unambiguously interpreted, both element and attribute names use Uniform Resource Identifiers (URI) to ensure naming conflicts do not occur across multiple XML formats. A URI is either a Uniform Resource Name (URN) or a Uniform Resource Locator (URL). The former is a location-independent identifier (like a UUID). The latter embeds location hints into the identifier itself. In either case, when URIs are used to disambiguate names in XML, they are treated as identifiers for an abstract set of names called a namespace. There is no requirement that dereferencing a namespace URI will yield anything useful. Rather, namespace URIs are simply opaque identifiers and nothing more. ...