"Untangle URIs, URLs, and URNs"—Dan Connolly
In information management, persistence and availability are in constant tension. This tension has led to separate technologies for Uniform Resource Names (URNs) and Uniform Resource Locators (URLs). Meanwhile, Uniform Resource Identifiers (URIs) are designed to serve as both persistent names and available locations. This article explains how to use the current URI standards with XML technologies, gives a history of URNs and URLs, and provides a perspective on the tension between persistence and availability.
I suggested this article idea to John Swanson, IBM developerWorks XML zone editor, but I thought that Connolly would be a much better person to write on the topic than I would. Nice to see it all published, and I'm glad to have a good resource to share with people when I'm asked the perennial question "what's the difference between a URL and a URI?"