XEP-xxxx: PubSub Since

Abstract:This specification defines a publish-subscribe feature that enables a subscriber to automatically receive pubsub and PEP notifications since its last logout time.
Authors:Joe Hildebrand, Peter Saint-Andre
Copyright:© 1999 - 2012 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status:ProtoXEP
Type:Standards Track
Version:0.0.1
Last Updated:2012-02-27

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document is not yet an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <http://xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.


Table of Contents


1. Introduction
2. How It Works
3. Determining Support
4. Security Considerations
5. IANA Considerations
6. XMPP Registrar Considerations
    6.1. Service Discovery Features

Appendices
    A: Document Information
    B: Author Information
    C: Legal Notices
    D: Relation to XMPP
    E: Discussion Venue
    F: Requirements Conformance
    G: Notes
    H: Revision History


1. Introduction

Many Publish-Subscribe [1] and Personal Eventing Protocol [2] services send notifications based on information about the presence of subscribers. This implies that subscribers might not receive notifications that were generated when they are offline at a particular resource. While Last Activity in Presence [3] defines a way for clients to include their last logout time, this specification closes the loop by defining how pubsub and PEP services can use the last logout information to send interim notifications to subscribers.

2. How It Works

As described in XEP-0256, a subscriber can indicate its last logout time when sending initial presence.

Example 1. Last Indication in Initial Presence

<presence from='juliet@capulet.com/balcony'>
  <query xmlns='jabber:iq:last' seconds='86511'/>
</presence>
  

Upon receiving such an indication, a pubsub or PEP service that supports presence-based notifications and the "pubsub-since" feature defined herein would behave as follows:

  1. The service MUST send to the subscriber all of the notifications stored in the relevant node's history that were generated since the last logout time.
  2. The service MAY adjust its definition of "interim notification" to account for reasonable clock skew (e.g., including notifications up to five minutes older than the subscriber's last logout time).
  3. The service SHOULD include only the final version of each pubsub notification (e.g., in case of items that were updated during the period when the subscriber was offline).
  4. The service SHOULD NOT include items that were removed from the node.
  5. The service MAY limit the number of notifications that it sends to avoid resource contraints.
  6. The service MAY include Result Set Management [4] data so that the subscriber can page through the set of interim notifications.

3. Determining Support

If a pubsub or PEP service supports the protocol defined herein, it MUST report that by including a Service Discovery [5] feature of "http://jabber.org/protocol/pubsub#since" in response to disco#info requests:

Example 2. Service discovery information request

<iq from='bard@shakespeare.lit/globe'
    id='sb2t1d49'
    to='pubsub.shakespeare.lit'
    type='get'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  

Example 3. Service discovery information response

<iq from='pubsub.shakespeare.lit'
    id='sb2t1d49'
    to='bard@shakespeare.lit/globe'
    type='result'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    <identity category='pubsub' type='service'/>
    <feature var='http://jabber.org/protocol/pubsub'/>
    <feature var='http://jabber.org/protocol/pubsub#auto-subscribe'/>
    <feature var='http://jabber.org/protocol/pubsub#presence-notifications'/>
    <feature var='http://jabber.org/protocol/pubsub#since'/>
  </query>
</iq>
  

4. Security Considerations

The number or cumulative size of the notifications published since the subscriber's last login time might be large, causing a significant load on the service. Implementations might consider truncating the interim notifications to avoid a denial of service.

5. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [6].

6. XMPP Registrar Considerations

6.1 Service Discovery Features

Support for the feature defined in this document is advertised by the ""http://jabber.org/protocol/pubsub#since"" Service Discovery feature.

The XMPP Registrar shall add this feature to its registry at <http://xmpp.org/registrar/disco-features.html>. The registration is as follows.

Registry Submission

<var>
  <name>http://jabber.org/protocol/pubsub#since</name>
  <desc>
    The pubsub or PEP service sends interim notifications upon receiving 
    initial presence containing the subscriber's last logout time.
  </desc>
  <doc>XEP-xxxx</doc>
</var>
    

Appendices


Appendix A: Document Information

Series: XEP
Number: xxxx
Publisher: XMPP Standards Foundation
Status: ProtoXEP
Type: Standards Track
Version: 0.0.1
Last Updated: 2012-02-27
Approving Body: XMPP Council
Dependencies: XMPP Core
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
This document in other formats: XML  PDF


Appendix B: Author Information

Joe Hildebrand

Email: jhildebr@cisco.com
JabberID: hildjj@jabber.org

Peter Saint-Andre

Email: stpeter@jabber.org
JabberID: stpeter@jabber.org
URI: https://stpeter.im/


Appendix C: Legal Notices

Copyright

This XMPP Extension Protocol is copyright © 1999 - 2012 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <http://xmpp.org/about-xmpp/xsf/xsf-ipr-policy/> or obtained by writing to XMPP Standards Foundation, 1899 Wynkoop Street, Suite 600, Denver, CO 80202 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.


Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.


Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".


Appendix G: Notes

1. XEP-0060: Publish-Subscribe <http://xmpp.org/extensions/xep-0060.html>.

2. XEP-0163: Personal Eventing Protocol <http://xmpp.org/extensions/xep-0163.html>.

3. XEP-0256: Last Activity in Presence <http://xmpp.org/extensions/xep-0256.html>.

4. XEP-0059: Result Set Management <http://xmpp.org/extensions/xep-0059.html>.

5. XEP-0030: Service Discovery <http://xmpp.org/extensions/xep-0030.html>.

6. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.


Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

Version 0.0.1 (2012-02-27)

First draft.

(psa)

END