Uniform Resource Identifiers (URI) Working Group

This WG has concluded

At the Stockholm IETF, the IESG decided that the URI WG had "completed" its original goals, and that its current work was too broad of scope for a single WG to ever attain consensus. New working groups will be formed to deal with the specific items of remaining work, to be announced on the URI mailing list. See also the URN working group.

RFC Revisions-in-progress and Internet-Drafts

Discussion of these and related topics takes place on the URI working group mailing list <>. A hypertext archive of the mailing list is available.
"An '.ipv6' Top Level Pseudo-Domain",
L. Masinter, J. Gettys, B. Carpenter, 16 Apr 1999.
The normal textual representation for IPv6 addresses as a set of colon-separated hexadecimal numbers does not work well with most deployed URL-parsing software. This document describes an alternate format which will pass unharmed through most URL-parsing software.
"Internationalized Uniform Resource Identifiers (IURI)",
L. Masinter, M. Duerst, 28 Jun 1999.
URIs [RFC 2396] are defined as sequences of characters chosen from a limited subset of the repertoire of ASCII characters both for transmission in network protocols and representation in spoken and written human communication.

This document defines IURIs (Internationalized URIs) as a sequence of characters from the repertorie of the UCS (Universal Character Set). A mapping of IURIs to URIs and guidelines for the use and deployment of IURIs in various elements of software that deal with URIs are given.

"Handling Internationalized Query Components in URLs",
M. Duerst, 30 Jul 1997.
HTTP and HTML provide the facility to query the user and return the results. This is usually done in the query component of an URL. This mechanisms works with full satisfaction for characters of the us- ascii repertoire. Due to the lack of an agreed encoding for other characters, the situation is much less satisfactory for characters outside the us-ascii repertoire.
"Requirements for Human Friendly Identifiers",
M. Mealling, 02 Oct 1998.
This document includes a set of requirements for an identifier that is engineered for human consumption. While the identifier is still machine consumable, the services and capabilities of the underlying system are designed with humans in mind. This includes concepts of geographic and context specific constraints, non-uniqueness, and natural language match semantics.

New URL Scheme Proposals

"A FTP URL Format",
J. Casey, 09 Jan 1997.
This document defines the format of Uniform Resource Locators (URL) for the File Transfer Protocol (FTP) using the general URL syntax defined in RFC xxxx, "Uniform Resource Locators (URL)".

It is a one of a suite of documents which replace RFC 1738, "Uniform Resource Locators", and RFC 1808, "Relative Uniform Resource Locators".

"A Gopher URL Format",
M. Krishnan, J. Casey, 04 Dec 1996.
This document defines the format of Uniform Resource Locators (URL) for the Gopher and Gopher+ protocols using the general URL syntax defined in RFC xxxx, "Uniform Resource Locators (URL)".

It is a one of a suite of documents which replace RFC 1738, "Uniform Resource Locators", and RFC 1808, "Relative Uniform Resource Locators".

"The 'news' URL scheme",
A. Gilman, 05 Mar 1998.
This document defines the format of Uniform Resource Locators (URLs) identifying news messages and groups. The syntax of 'news' URLs from RFC 1738 is extended to allow specification of the site from which the message is to be sought and to incorporate protections via 'snews' URLs. This combines into the 'news' scheme enough capability so that the previously-proposed 'nntp' scheme can be retired and URL usage simplified.
"The hnews URL scheme",
T. Stockwell, 17 Jun 1998.
HNEWS [1] is an HTTP-tunneling variant of the NNTP news protocol. This document defines the format of Uniform Resource Locators(URLs) identifying news messages and groups provided by HNEWS servers. The syntax of 'hnews' URLs is designed to be compatible with the current common usage of the 'news' URL scheme. Specifically, the 'hnews' URL scheme is designed according to recommendations made in [NEWS_URL_SCHEME]. [NEWS_URL_SCHEME] is based on the general specification of all URL schemes in 'Uniform Resource Locators (URL): Generic Syntax and Semantics' [RFC URI SYNTAX].
"The RWhois Uniform Resource Locator",
S. Williamson, M. Mealling, 02 Aug 1997.
RWhois is an Internet directory access protocol, defined in RFC1714 [1] and RFC2167 [3]. This document describes a format for an RWhois Uniform Resource Locator (URL) that will allow Internet clients to have direct access to the RWhois protocol. An RWhois URL will represent a single query to an RWhois server.
"WHOIS++ URL Specification",
M. Hamilton, 13 Mar 1998.
This document defines a new Uniform Resource Locator (URL) scheme "whois++", which provides a convention within the URL framework for referring to WHOIS++ servers and the data held within them.
"SDP URL Scheme",
K. Fujikawa, 07 Aug 1998.
This document describes a format for an Session Description Protocol Uniform Resource Locator (SDP URL) which will allow Internet clients to have direct access to multimedia sessions.
"The service: URL Scheme",
E. Guttman, 22 Nov 1996.
The service: URL scheme is used to provide service access information for arbitrary network services. These URLs provide an extensible framework for client based network software to obtain configuration information required to make use of network services. A service: URL may be accompanied by a set of well defined attributes which define the characteristics of the service. These attributes may convey protocol configuration information to client software or service characteristics meaningful to end users. This document describes how to define and standardize new service types and attributes for use with the service: scheme and provides examples.
"irc: URL scheme",
M. Mirashi, 26 Aug 1996.
A new URL scheme "irc:" is defined. The irc URL scheme is used to refer to either IRC (Internet Relay Chat) servers or individual entities (channels or people) on IRC servers.
"Videotex URL Specification",
D. Mavrakis, H. Layec, K. Kartmann, 20 May 1997.
A new URL scheme, "videotex" is defined. It allows videotex client software or terminals to connect to videotex services compliant to the ITU-T and ETSI videotex standards.
"Requirements TV Broadcast URI Schemes",
W. ten Kate, G. Thomas, C. Finseth, 18 Nov 1998.
This document lists the requirements posed to URI schemes for use in TV Broadcast environments. The document summarizes the outcome of discussions on this subject by the W3C TV-Web Interest Group [1].
"Uniform Resource Identifiers for Television Broadcasts",
D. Zigmond, M. Vickers, 07 Jan 2000.
World-Wide Web browsers are starting to appear on a variety of consumer electronic devices, such as television sets and television set-top boxes, which are capable of receiving television programming from either terrestrial broadcast, satellite broadcast, or cable. In this context there is a need to reference television broadcasts using the URI format described in [RFC 2396]. This document describes a widely-implemented URI scheme to refer to such broadcasts.
"URLs for GSM Short Message Service",
A. Vaha-Sipila, 19 May 1999.
This document specifies a URL (Uniform Resource Locator) scheme 'gsm-sms' for specifying a recipient for an alphanumeric message (Short Message) in a GSM-based mobile phone system. Short Messages are two-way paging messages that can be sent from a suitable equipped computer or a phone.
"URLs for Telephone Calls",
A. Vaha-Sipila, 29 Dec 1999.
This document specifies URL (Uniform Resource Locator) schemes 'tel', 'fax' and 'modem' for specifying the location of a terminal in the phone network and the connection types (modes of operation) that can be used to connect to that entity. This specification covers voice calls (normal phone calls, answering machines and voice messaging systems), facsimile (telefax) calls and data calls, both for POTS and digital/mobile subscribers.
"Conversational Multimedia URLs",
P. Cordell, 23 Dec 1997.
The evolving technologies for real-time conversation over the Internet require URLs to provide user contact information. As there are many protocols (including some that are not Internet based) that can be used for inter-user conversation, this document describes a two stage transaction process for obtaining a URL that can be used to initiate conversation. The first stage involves retrieving a list of protocol specific URLs in a MIME encoded file. The MIME type enables an appropriate application to be launched which will analyse the presented URLs and select the most appropriate one. The second stage involves interpreting the protocol specific URL and initiating the conversation. The protocol specific URLs are encoded in a URL form so that they can be embedded directly into HTML pages. This allows the first stage to be omitted. The document describes the format of the MIME encoded list of URLs, and the format of a number of protocol specific URLs.
"Stream URI Scheme",
F. Kenji, K. Shinobu, T. Tsuyoshi, 03 Jan 2000.
This document describes the Stream Uniform Resource Identifier which allows Internet clients to have direct access to multimedia streams.
"An SMTP URL Interface",
R. Earhart, 29 Dec 1997.
It is occasionally useful to be able to reference a generic server to be used for message submission. URLs provide a good mechanism for refering to arbitrary network resources. The SMTP URL scheme allows a URL to specify an SMTP server, thus allowing other protocols to use a general ''URL to be used for message delivery'' in place of an explicit reference to SMTP.
"The 'eid' URL Scheme",
C. Finseth, 02 Apr 1999.
This document defines a new URL scheme, 'eid'. This scheme provides a mechanism by which the local application can reference data that has been obtained by other, non-URL scheme means. The scheme is intended to provide a general escape mechanism to allow access to information for applications that are too specialized to justify their own schemes.
See also Historical Documents.

Requests for Comment

Functional Recommendations for Internet Resource Locators (RFC 1736) (22415 bytes), J. Kunze, February 1995.
This document specifies a minimum set of requirements for Internet resource locators, which convey location and access information for resources. Typical examples of resources include network accessible documents, WAIS databases, FTP servers, and Telnet destinations.

Functional Requirements for Uniform Resource Names (RFC 1737) (16337 bytes), K. Sollins, L. Masinter, December 1994.
This document specifies a minimum set of requirements for a kind of Internet resource identifier known as Uniform Resource Names (URNs). URNs fit within a larger Internet information architecture, which in turn is composed of, additionally, Uniform Resource Characteristics (URCs), and Uniform Resource Locators (URLs). URNs are used for identification, URCs for including meta-information, and URLs for locating or finding resources. It is provided as a basis for evaluating standards for URNs. The discussions of this work have occurred on the mailing list and at the URI Working Group sessions of the IETF.

Uniform Resource Locators (URL) (RFC 1738) (51348 bytes), T. Berners-Lee, L. Masinter, M. McCahill, December 1994. Updated by RFC 2396.
This document specifies a Uniform Resource Locator (URL), the syntax and semantics of formalized information for location and access of resources via the Internet.

Relative Uniform Resource Locators (RFC 1808) (34950 bytes), R. Fielding, June 1995, Updated by RFC 2396.
A Uniform Resource Locator (URL) is a compact representation of the location and access method for a resource available via the Internet. When embedded within a base document, a URL in its absolute form may contain a great deal of information which is already known from the context of that base document's retrieval, including the scheme, network location, and parts of the url-path. In situations where the base URL is well-defined and known to the parser (human or machine), it is useful to be able to embed URL references which inherit that context rather than re-specifying it in every instance. This document defines the syntax and semantics for such Relative Uniform Resource Locators.

The LDAP URL Format (RFC 2255) (20685 bytes) LDAP-WG, T. Howes, M. Smith, December 1997.
LDAP is the Lightweight Directory Access Protocol, defined in [1], [2] and [3]. This document describes a format for an LDAP Uniform Resource Locator. The format describes an LDAP search operation to perform to retrieve information from an LDAP directory. This document replaces RFC 1959. It updates the LDAP URL format for version 3 of LDAP and clarifies how LDAP URLs are resolved. This document also defines an extension mechanism for LDAP URLs, so that future documents can extend their functionality, for example, to provide access to new LDAPv3 extensions as they are defined.

Uniform Resource Locators for Z39.50 (RFC 2056) (14204 bytes), R. Denenberg, J. Kunze, D. Lynch, November 1996.
Z39.50 is an information retrieval protocol that does not fit neatly into a retrieval model designed primarily around the stateless fetch of data. Instead, it models a general user inquiry as a session-oriented, multi-step task, any step of which may be suspended temporarily while the server requests additional parameters from the client before continuing.

Content-ID and Message-ID Uniform Resource Locators (RFC 2111) (9113 bytes), E. Levinson, March 1997. Obsoleted by RFC 2392.
The Uniform Resource Locator (URL) schemes, "cid:" and "mid:" allow references to messages and the body parts of messages. For example, within a single multipart message, one HTML body part might include embedded references to other parts of the same message. This document is a product of the MIME Encapsulation of Aggregate HTML Documents Working Group of the IETF.

VEMMI URL Specification (RFC 2122), (25043 bytes), D. Mavrakis, H. Layec, K. Kartmann, March 1997.
A new URL scheme, "vemmi" is defined. It allows VEMMI client software and VEMMI terminals to connect to multimedia interactive services compliant to the VEMMI standard (Enhanced Man-Machine Interface for Videotex and Multimedia/Hypermedia Information Retrieval Services), sometimes abbreviated as "VErsatile MultiMedia Interface".

IMAP URL Scheme (RFC 2192), (31426 bytes), C. Newman, September 1997.
IMAP [IMAP4] is a rich protocol for accessing remote message stores. It provides an ideal mechanism for accessing public mailing list archives as well as private and shared message stores. This document defines a URL scheme for referencing objects on an IMAP server.

NFS URL Scheme (RFC 2224), (22726 bytes), B. Callaghan, October 1997.
A new URL scheme, 'nfs' is defined. It is used to refer to files and directories on NFS servers using the general URL syntax defined in RFC 1738, "Uniform Resource Locators (URL)".

The mailto URL scheme (RFC 2368), (16502 bytes), P. Hoffman, L. Masinter, J. Zawinski, July 1998.
This document defines the format of Uniform Resource Locators (URL) for designating electronic mail addresses. It is one of a suite of documents which replace RFC 1738, 'Uniform Resource Locators', and RFC 1808, 'Relative Uniform Resource Locators'. The syntax of 'mailto' URLs from RFC 1738 is extended to allow creation of more RFC 822 messages by allowing the URL to express additional header and body fields.

The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields (RFC 2369), (30853 bytes), G. Neufeld, J. Baer, July 1998.
This is a proposal for additional header fields to be added to email messages sent by email distribution lists. The content of each new field is typically a URL - usually mailto [RFC2368] - which locates the relevant information or performs the command directly. MTAs generating the header fields SHOULD usually include a mailto based command, in addition to any other protocols used, in order to support users who do not have access to non-mail-based protocols.

POP URL Scheme (RFC 2384), (13649 bytes), R. Gellens, August 1998.
This memo defines a URL scheme for referencing a POP mailbox.

Content-ID and Message-ID Uniform Resource Locators (RFC 2392) (11141 bytes), E. Levinson, August 1998.
The Uniform Resource Locator (URL) schemes, "cid:" and "mid:" allow references to messages and the body parts of messages. For example, within a single multipart message, one HTML body part might include embedded references to other parts of the same message.

Uniform Resource Identifiers (URI): Generic Syntax (RFC 2396), (84503 bytes),
T. Berners-Lee, R. Fielding, L. Masinter, August 1998.
Additional information is available at Roy's test site.
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.

The "data" URL scheme (RFC 2397), (9514 bytes),
L. Masinter, August 1998.
A new URL scheme, "data", is defined. It allows inclusion of small data items as "immediate" data, as if it had been included externally.

URI Resolution Services Necessary for URN Resolution (RFC 2483), (30518 bytes),
M. Mealling, R. Daniel, Jr., January 1999.
Retrieving the resource identified by a Uniform Resource Identifier (URI) [1] is only one of the operations that can be performed on a URI. One might also ask for and get a list of other identifiers that are aliases for the original URI or a bibliographic description of the resource the URI denotes, for example. This applies to both Uniform Resource Names (URNs) and Uniform Resource Locators (URLs). Uniform Resource Characteristics (URCs) are discussed in this document but only as descriptions of resources rather than identifiers.

Registration Procedures for URL Scheme Names (RFC 2717), (19780 bytes),
R. Petke, I. King, November 1999.
This document defines the process by which new URL scheme names are registered.

Guidelines for new URL Schemes (RFC 2718), (19208 bytes),
L. Masinter, H. Alvestrand, D. Zigmond, R. Petke, November 1999.
A Uniform Resource Locator (URL) is a compact string representation of the location for a resource that is available via the Internet. This document provides guidelines for the definition of new URL schemes.

Preferred Format for Literal IPv6 Addresses in URL's (RFC 2732), (7984 bytes),
R. Hinden, B. Carpenter, L. Masinter, December 1999.
This document defines the format for literal IPv6 Addresses in URL's for implementation in World Wide Web browsers. This format has been implemented in the IPv6 versions of several widely deployed browsers including Microsoft Internet Explorer, Mozilla, and Lynx. It is also intended to be used in the IPv6 version of the service location protocol.

This document includes an update to the generic syntax for Uniform Resource Identifiers defined in RFC 2396 [URL]. It defines a syntax for IPv6 addresses and allows the use of "[" and "]" within a URI explicitly for this reserved purpose.

Related Work

Roy Fielding Department of Information and Computer Science
University of California, Irvine, CA 92697-3425
Last modified: 06 Oct 2000