A URI is a Uniform Resource Identifier, a fundamental aspect of the Internet and the World Wide Web. See the Wikipedia entry for more information.
W3C URI Interest Group projects
One of the planned activities of the W3C's URI Interest Group is to fully retire RFC 1738. Much of the RFC is already obsolete, but portions of it—the parts that describe specific URI schemes—are still in effect.
Development of a replacement RFC that describes the 'file' URI scheme occasionally sees some momentum, but tends to stall and get bogged down in editorial details. It was suggested that a wiki might allow for better collaboration.
To that end, Offset is hosting a workspace for the new 'file' URI scheme Internet Draft.