Using XML with Legacy Business Applications

URIs, URNs, and URLs

The Schema Recommendation specifies that namespaces have a name expressed as a URI. We're all familiar with URLs from the Web, but fewer people have heard of URIs or URNs or really know what they mean. These terms are all defined in standards maintained by the Internet Engineering Task Force (IETF). IETF standards originate as Requests for Comment (RFC), so the standards that define these terms are referenced by their RFC numbers. Pointers to them are listed in the Resources section at the end of the chapter.

• Uniform Resource Identifier (URI): RFC 2396 defines a URI as “a compact string of characters for identifying an abstract or physical resource.” This is the general class from which all other types of identifiers such ...