Jabber, Inc. August 20, 2004

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1 Network Working Group Internet-Draft Expires: February 18, 2005 P. Saint-Andre Jabber Software Foundation J. Hildebrand Jabber, Inc. August 20, 2004 Transporting Atom Notifications over the Extensible Messaging and Presence Protocol (XMPP) draft-saintandre-atompub-notify-00 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its 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 and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at The list of Internet-Draft Shadow Directories can be accessed at This Internet-Draft will expire on February 18, Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This memo describes a method for notifying interested parties about changes in syndicated information encapsulated in the Atom feed format, where such notifications are delivered via an extension to the Extensible Messaging and Presence Protocol (XMPP) for publish-subscribe functionality. Saint-Andre & Hildebrand Expires February 18, 2005 [Page 1]

2 Table of Contents 1. Introduction Overview Terminology Discussion Venue Process Flows Notification of Entry Creation Notification of Entry Modification Notification of Entry Deletion IANA Considerations Security Considerations References Normative References Informative References Authors Addresses Intellectual Property and Copyright Statements Saint-Andre & Hildebrand Expires February 18, 2005 [Page 2] 1. Introduction 1.1 Overview The Atom Publishing Format and Protocol Working Group has been chartered to develop two technologies relevant to content syndication: 1. A data format for syndication of information about

3 periodically-updated resources (such as weblog entries and news stories) available on the World Wide Web. 2. A protocol for publishing, editing, deleting, and otherwise managing such resources. Content syndication follows a classic "observer" or "publish-subscribe" design pattern: a person or application publishes information to a "channel", and an event notification (or the data itself) is broadcasted to all those who are interested in knowing when information is published or modified for that channel. On the Internet today, publication of periodically-updated resources is handled by means of standard technologies such as [HTTP], and it is not envisioned that this will change since [ATOM-API] specifies the use of HTTP for publication. However, existing methods for learning that a resource has been updated are currently limited to "polling" for changes via HTTP, which is inherently inefficient. What is needed is a technology that can be relied on to "push" information only when a resource undergoes a state change, and only to those who are interested in learning about such state changes. One possible technology for doing so is , since [SMTP] provides a way to initiate the sending of information from "publishers" to "subscribers" (think, for example, of lists such as those used to announce newly-published RFCs). While is one possible solution, it is not necessarily the best solution for Atom; in particular, [ATOM-FORMAT] defines an XML data format for content syndication, which implies that it might be beneficial to use a native XML delivery mechanism rather than to attach a special XML media type to messages. Thankfully, a specialized XML delivery protocol has been developed through the IETF: the Extensible Messaging and Presence Protocol (XMPP) as specified in [XMPP-CORE]. XMPP has the added benefit of being optimized for near-real-time data delivery, which may be important in applications of Atom that require subscribers to be notified about syndicated content in a highly timely manner. While the semantics of a normal XMPP <message/> element may be suitable for Atom content notifications, there also exists an XMPP extension that provides more structured communications in the context Saint-Andre & Hildebrand Expires February 18, 2005 [Page 3] of information "channels" or "nodes" of the kind that are used in content syndication. This extension is specified in [XMPP-PUBSUB] and may be especially useful for delivering notifications related to changes in Atom resources. Therefore, this memo describes a method for notifying interested parties about changes in syndicated information encapsulated in the Atom feed format, where such notifications are delivered via the XMPP publish-subscribe extension. 1.2 Terminology This document inherits terminology from [ATOM-API], [ATOM-FORMAT], [XMPP-CORE], and [XMPP-PUBSUB]. The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [TERMS].

4 1.3 Discussion Venue The authors welcomes discussion and comments related to the topics presented in this document. The preferred forum is the mailing list, for which subscription information and archive links are available at << 2. Process Flows The following process flows demonstrate how Atom-formatted data (specifically, feed entries) can be delivered using the XMPP pubsub extension. The actors in these process flows are an application and one or more XMPP users. The application acts as a translator between HTTP and XMPP, since it generates XMPP pubsub requests when certain events occur at an Atom-aware HTTP service (e.g., an HTTP POST to create a new dynamic resource). The XMPP pubsub service then translates those pubsub requests into notifications that are sent to a potentially large number of XMPP users who have subscribed to such events (e.g., who have asked to receive an XMPP notification whenever a new dynamic resource is created for a certain Atom "channel"). Of course, an XMPP user is not necessarily a human, and could represent another application on the XMPP network (e.g., a chatroom bot or a content management system). Note well that an HTTP user (e.g., a weblog author) would still publish information using the protocol defined in [ATOM-API]; the process flows described herein enable the HTTP service with which an HTTP user interacts to generate notifications that are delivered via an XMPP pubsub service to a potentially large number of XMPP users Saint-Andre & Hildebrand Expires February 18, 2005 [Page 4] who want to receive such information. We can visualize the architecture as follows: HTTP User [Atom API] HTTP Service [XMPP Pubsub] XMPP Pubsub Service [XMPP Pubsub] XMPP User

5 Notification of Entry Creation When a content author publishes a new dynamic resource, many entities may be interested in learning that the resource is now available. The process flow is as follows: o Author publishes a new entry to the HTTP service via the Atom API. o The HTTP service sends data for the new Atom entry in an XMPP pubsub "publish" request to a specific node at the XMPP pubsub service. o The XMPP pubsub service sends an XMPP message notification to each XMPP entity that is subscribed to the pubsub node. The result is that the XMPP subscribers will receive something close to real-time notification whenever a new feed entry has been published. Obviously the first step is out of scope for this memo, since it is described in [ATOM-API]. The XMPP protocols for the last two steps are shown below. Saint-Andre & Hildebrand Expires February 18, 2005 [Page 5] First the HTTP service sends an XMPP pubsub "publish" request to the XMPP pubsub service: <iq type= set from= http-service.example.org to= pubsub.example.org id= publish1 > <pubsub xmlns= > <publish node= > <item id= i1s2d3f4g5h6bjeh936 > <entry version= draft-ietf-atompub-format-01: do not deploy xmlns= > <title>atom-powered Robots Run Amuck</title> <link rel= alternate type= text/html href= /> <id>tag:example.org,2003:3.2397</id> <issued> t08:29:29-04:00</issued> <modified> t08:29:29-04:00</modified> </entry> </item> </publish> </pubsub> </iq> The XMPP pubsub service then sends a pubsub notification to each XMPP subscriber; depending on pubsub node configuration, the notification may or may not contain the Atom payload (we assume here that the payload will be delivered).

6 <message from= pubsub.example.org to= > <event xmlns= > <items node= > <item id= i1s2d3f4g5h6bjeh936 > <entry version= draft-ietf-atompub-format-01: do not deploy xmlns= > <title>atom-powered Robots Run Amuck</title> <link rel= alternate type= text/html href= /> <id>tag:example.org,2003:3.2397</id> <issued> t08:29:29-04:00</issued> <modified> t08:29:29-04:00</modified> </entry> </item> </items> </event> Saint-Andre & Hildebrand Expires February 18, 2005 [Page 6] </message> 2.2 Notification of Entry Modification When a content author updates an existing dynamic resource, many entities may be interested in learning that the resource has been modified. The process flow is as follows: o Author updates an existing entry at the HTTP service via the Atom API. o The HTTP service sends data for the updated Atom entry in an XMPP pubsub "publish" request to a specific node at the XMPP pubsub service, specifying the same Item ID as previously supplied. o The XMPP pubsub service sends an XMPP message notification to each XMPP entity that is subscribed to the pubsub node. First the HTTP service sends an XMPP pubsub "publish" request to the XMPP pubsub service (note the modified title and time): <iq type= set from= http-service.example.org to= pubsub.example.org id= publish2 > <pubsub xmlns= > <publish node= > <item id= i1s2d3f4g5h6bjeh936 > <entry version= draft-ietf-atompub-format-01: do not deploy xmlns= > <title>atom-powered Robots Run Amok</title> <link rel= alternate type= text/html href= /> <id>tag:example.org,2003:3.2397</id> <issued> t08:29:29-04:00</issued> <modified> t08:41:41-04:00</modified> </entry> </item> </publish>

7 </pubsub> </iq> Subject to node configuration and/or subscription options, each XMPP subscriber would then receive a pubsub notification, which may or may not contain the Atom payload. Saint-Andre & Hildebrand Expires February 18, 2005 [Page 7] <message from= pubsub.example.org to= alice@example.net > <event xmlns= > <items node= > <item id= i1s2d3f4g5h6bjeh936 > <entry version= draft-ietf-atompub-format-01: do not deploy xmlns= > <title>atom-powered Robots Run Amok</title> <link rel= alternate type= text/html href= /> <id>tag:example.org,2003:3.2397</id> <issued> t08:29:29-04:00</issued> <modified> t08:41:41-04:00</modified> </entry> </item> </items> </event> </message> 2.3 Notification of Entry Deletion If a content author deletes an existing dynamic resource, many entities may be interested in learning that the resource is no longer available. The process flow is as follows: o Author deletes an existing entry at the HTTP service via the Atom API. o The HTTP service sends an XMPP pubsub "retract" request to a specific node at the XMPP pubsub service, specifying the same Item ID as previously supplied. o The XMPP pubsub service sends an XMPP message notification to each XMPP entity that is subscribed to the pubsub node. First the HTTP service sends an XMPP pubsub "retract" request to the XMPP pubsub service: <iq type= set from= http-service.example.org to= pubsub.example.org id= delete1 > <pubsub xmlns= > <retract node= > <item id= i1s2d3f4g5h6bjeh936 /> </retract> </pubsub>

8 </iq> Saint-Andre & Hildebrand Expires February 18, 2005 [Page 8] Subject to node configuration and/or subscription options, each XMPP subscriber would then receive a pubsub notification that the item was deleted. <message from= pubsub.example.org to= alice@example.net > <event xmlns= > <items node= > <retract id= i1s2d3f4g5h6bjeh936 /> </items> </event> </message> 3. IANA Considerations This document requires no action on the part of the IANA. 4. Security Considerations Detailed security considerations for the relevant protocols profiled in this memo are given in [ATOM-API], [ATOM-FORMAT], [XMPP-CORE], and [XMPP-PUBSUB]; this memo introduces no new security concerns above and beyond those described in the foregoing specifications. 5. References 5.1 Normative References [ATOM-API] Gregorio, J. and R. Sayre, "The Atom Publishing Protocol", draft-ietf-atompub-protocol-01 (work in progress), July [ATOM-FORMAT] Nottingham, M., "The Atom Syndication Format", draft-ietf-atompub-format-01 (work in progress), July [TERMS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March [XMPP-CORE] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", draft-ietf-xmpp-core-24 (work in progress), May [XMPP-PUBSUB]

9 Saint-Andre & Hildebrand Expires February 18, 2005 [Page 9] Millard, P., "Publish-Subscribe", JSF JEP 0060, July Informative References [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June [SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April Authors Addresses Peter Saint-Andre Jabber Software Foundation Joe Hildebrand Jabber, Inc. Saint-Andre & Hildebrand Expires February 18, 2005 [Page 10]

10 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Saint-Andre & Hildebrand Expires February 18, 2005 [Page 11]