HTTP/1.1 200 OK Date: Tue, 09 Apr 2002 09:50:27 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Fri, 13 Oct 1995 23:00:00 GMT ETag: "3240e9-17d1-307eef70" Accept-Ranges: bytes Content-Length: 6097 Connection: close Content-Type: text/plain MIMESGML Working Group E. Levinson Internet Draft: CID and MID URLs Accurate Info. Sys., Inc. October 12, 1995 Content-ID and Message-ID Uniform Resource Locators This draft document is being circulated for comment. Please send your comments to the authors or to the ietf-822 mail list . If consensus is reached, this Access Type may be registered with IANA and this document may be submitted to the RFC editor as an Informational protocol specification. Status of this Memo This document is an Internet Draft; Internet Drafts are working documents of the Internet Engineering Task Force (IETF) its Areas, and Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. They may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress". Please check the abstract listing in each Internet Draft directory for the current status of this or any other Internet Draft. Abstract The Uniform Resource Locator (URL) scheme, "cid", allows compound or aggregate objects in a multipart mail message to refer to one another by their body part labels. 1. Introduction There is a desire to refer to email or netnews messages and the body parts of such messages using Uniform Resource Locators (URLs). The MID and CID schemes described below permit such references. The use of [MIME] within email to convey Web pages and their associated images requires a URL scheme to permit the HTML to refer to the images included in the message. A Content- ID Uniform Resource Locator serves that purpose. Similarly NetNews readers use Message-IDs to link related messages together. The Message-ID URL provides a scheme for that purpose. 2. The MID and CID URL Schemes Levinson Expires December 31, 1995 [Page 1] Internet Draft Access Type Content-ID RFC1738 [URL] reserves the scheme "cid" for Content-ID. This memorandum defines the syntax for the cid URL. Because a Message-ID scheme uses the same syntatic elements both are presented together. The URLs takes the form cidurl = "cid" ":" id-spec midurl = msgmid / cidmid msgmid = "mid" ":" id-spec cidmid = msgmid "#" cidurl id-spec = local-part "@" hostname ; globally unique local-part = 1*uchar where id-spec is a restricted form of "addr-spec" as defined in [RFC822] and hostname and uchar are defined in [RFC1738, sec 3.1]. The purpose of the restriction on addr-spec is to eliminate special characters from the cid URL. Such characters can be problematical in many environments (e.g., HTML and SGML) in which the cidurl may be used. Special characters are representable, however, by using the escape mechanism provided in [RFC1738] Cidurls and midurls are a subset of MIME content-IDs and RFC822 message-IDs respectively. A msgmid refers to the entire message and the cidmid refers to a single body part within the referenced message. The cidurls and midurls differ from message-ids and MIME content-ids in the inclusion of the scheme part and in the omission of the leading and trailing brackets, "<" and ">", and the restricted character set. To transform a cidurl or midurl into a valid content-id or message-id, surround the id-spec part with the enclosing brackets, i.e., content-id = "<" id-spec ">". message-id = "<" id-spec ">". Cidurls and midurls are globally unique [MIME, p.19]. A common technique for generating a globally unique cidurl and midurl uses a time and date stamp with the local host's domain name, e.g., 950124.162336@XIson.com. 3. Security Security issues are not addressed in this memorandum. Levinson Expires December 31, 1995 [Page 2] Internet Draft Access Type Content-ID 4. References [822] Crocker, D., Standard for the Format of ARPA Internet Text Mes- sages, August 1982, University of Delaware, RFC 822. [MIME] Borenstein, N. and Freed, N., MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies, June 1992, RFC 1341. [SGML] ISO 8879:1988, Information processing -- Text and office systems -- Standard Generalized Markup Language (SGML). [URL] Berners-Lee, T., Masinter, L., and McCahill, M., Uniform Resource Locators (URL), December 1994, RFC 1738. 5. Acknowledgements This work reflects the ideas freely provided to the author by Harald T. Alvestrand, UNINETT, including Tim Berners-Lee, W3O, who pointed me at the idea of using a URL "scheme" in the SGML encapsulation proposal, Daniel W. Connolly, HAL, and Roy T. Fielding, UCI. 6. Author's Address Edward Levinson Accurate Information Systems, Inc. 2 Industrial Way Eatontown, NJ 07724-2265 USA +1 908 389 5550 Levinson Expires December 31, 1995 [Page 3]