World Wide Web Consortium

MIT Laboratory for Computer Science, NE43-356 545 Technology Square Cambridge MA 02139 +1(617)258-8682 timbl@w3.org

Department of Information and Computer Science

University of California, Irvine Irvine CA 92697-3425 +1(949)824-1715 fielding@ics.uci.edu

Xerox PARC

3333 Coyote Hill Road Palo Alto CA 94034 +1(415)812-4333 masinter@parc.xerox.com

Applications uniform resource URI A Uniform Resource Identifier (URI) is a compact string of characters for identifying an abstract or physical resource. This document defines the generic syntax of URI, including both absolute and relative forms, and guidelines for their use; it revises and replaces the generic definitions in RFC 1738 and RFC 1808. This document defines a grammar that is a superset of all valid URI, such that an implementation can parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier type. This document does not define a generative grammar for URI; that task will be performed by the individual specifications of each URI scheme. This paper describes a "superset" of operations that can be applied to URI. It consists of both a grammar and a description of basic functionality for URI. To understand what is a valid URI, both the grammar and the associated description have to be studied. Some of the functionality described is not applicable to all URI schemes, and some operations are only possible when certain media types are retrieved using the URI, regardless of the scheme used.