XEP-0296: Best Practices for Resource Locking

Abstract:This document specifies best practices to be followed by Jabber/XMPP clients about when to lock into, and unlock away from, resources.
Author:Matthew Miller
Copyright:© 1999 - 2014 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status:Deferred
Type:Informational
Version:0.2
Last Updated:2011-08-18

WARNING: Consideration of this document has been Deferred by the XMPP Standards Foundation. Implementation of the protocol described herein is not recommended.


Table of Contents


1. Introduction
2. General Rules
    2.1. Initial Conversation State
    2.2. Locking a Conversation
    2.3. Unlocking a Conversation
    2.4. Interactions with Chat States
3. User Agent Implementation Notes
    3.1. User Experience Considerations
    3.2. Idle Conversations
    3.3. Overall Inactivity
4. Security Considerations
5. IANA Considerations
6. XMPP Registrar Considerations

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

The goal of this specification is to provide implementation guidance for XMPP clients to improve the user experience when maintaining a chat conversation between the user and a conversee. Section 5.1 of XMPP IM [1] defines the concept of a "one-to-one chat session" and recommends that clients support the behavior described there, including:

  1. Send the first message in a chat session to the bare JID <localpart@domain.tld> of the intended recipient
  2. Send messages to the full JID <localpart@domain.tld/resource> only after receiving a reply from the recipient (this is called "locking" into that full JID).
  3. Send messages to the bare JID again if the presence of the recipient changes in any way (this is called "unlocking" from the full JID).

However, following only these guidelines can still lead to "disjointed" chat conversations in clients, epsecially if multiple resources are in play.

This specification reinforces the recommendations from XMPP-IM and provides additional implementation guidance to developers of XMPP clients.

2. General Rules

2.1 Initial Conversation State

A client MUST start conversations in the unlocked state. In this state, a client MUST send <message/>s to a conversee's bare JID.

2.2 Locking a Conversation

Once a client receives a chat <message/> from the conversee, whether or not this client initiated the conversation, it MUST lock the conversation. The client MUST remember the conversee's full JID and send further correspondence to this full JID until one of the unlocking conditions are met.

2.3 Unlocking a Conversation

A client MUST unlock a chat session from a resource when one of the following conditions is met:

2.4 Interactions with Chat States

If a client supports Chat State Notifications (XEP-0085) [2], then the following additional considerations apply:

3. User Agent Implementation Notes

This section is non-normative, but provides additional guidelines for clients that interact directly with users.

3.1 User Experience Considerations

To further improve the user experience, clients are strongly encouraged to implement Chat State Notifications and adhere to the recommendations from Best Practices for Message Threads (XEP-0201) [3].

3.2 Idle Conversations

A client MAY take into account the lack of activity of a conversation. Exactly how much inactivity constitutes an idle conversation is left to implementations to determine.

3.3 Overall Inactivity

A client MAY take into account the overall lack of activity of a user, in which case it is RECOMMENDED the client send a <presence/> update to trigger any conversations to unlock. The exact conditions and <presence/> information conveyed is left to implementations to determine.

4. Security Considerations

This document introduces no known security vulnerabilities.

5. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [4].

6. XMPP Registrar Considerations

This document requires no interaction with the XMPP Registrar [5].


Appendices


Appendix A: Document Information

Series: XEP
Number: 0296
Publisher: XMPP Standards Foundation
Status: Deferred
Type: Informational
Version: 0.2
Last Updated: 2011-08-18
Approving Body: XMPP Council
Dependencies: XMPP Core, XMPP IM, XEP-0085, XEP-0201
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
Source Control: HTML
This document in other formats: XML  PDF


Appendix B: Author Information

Matthew Miller

Email: linuxwolf@outer-planes.net
JabberID: linuxwolf@outer-planes.net


Appendix C: Legal Notices

Copyright

This XMPP Extension Protocol is copyright © 1999 - 2014 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 6120) and XMPP IM (RFC 6121) 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. RFC 6121: Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence <http://tools.ietf.org/html/rfc6121>.

2. XEP-0085: Chat State Notifications <http://xmpp.org/extensions/xep-0085.html>.

3. XEP-0201: Best Practices for Message Threads <http://xmpp.org/extensions/xep-0201.html>.

4. 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/>.

5. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://xmpp.org/registrar/>.


Appendix H: Revision History

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

Version 0.2 (2011-08-18)

Expanded intro with a short problem description; moved chat states considerations to their own section; tightened requirement regarding a message from different resource from MAY to SHOULD; loosened requirement regarding a message with 'gone' from MUST to SHOULD; added missing but required sections

(mam)

Version 0.1 (2011-04-11)

Initial published version.

(psa)

Version 0.0.1 (2011-03-14)

Initial draft

(mm)

END