XEP-0296: Best Practices for Resource Locking

WARNING: This Informational document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the best practice or protocol profile described herein is encouraged in exploratory implementations, although production systems are advised to carefully consider whether it is appropriate to deploy implementations of this protocol before it advances to a status of Draft.

1. Introduction
2. General Rules
    2.1. Initial Conversation State
    2.2. Locking a Conversation
    2.3. Unlocking a Conversation
3. User Agent Implementation Notes
    3.1. User Experience Considerations
    3.2. Idle Conversations
    3.3. Overall Inactivity

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

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:

This specification reinforces the recommendations from XMPP-IM and provides additional implementation guidance to developers of XMPP clients. It is hoped that wider deployment of clients that adhere to the advice provided here will result in an improved user experience.

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:

A <message/> from the same bare JID, but a different resource, is received. In this case, the client MAY lock to the new resource; or the client MAY revert to the initial state, sending any following correspondence to the conversee's bare JID.
A <message/> with a <gone xmlns='http://jabber.org/protocol/chatstates'/> chat state. In this case, the client MUST consider the conversation ended. Any further correspondence MUST be sent with a new threadID and to the bare JID.
any <presence/> update from any resource for the conversee's bare JID, including <presence type='unavailable'/>. The client SHOULD revert to the initial state, sending any following correspondence to the conversee's bare JID.

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 [2] and adhere to the recommendations from Best Practices for Message Threads [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.

Appendices

Appendix A: Document Information

Series: XEP
Number: 0296
Publisher: XMPP Standards Foundation
Status: Experimental
Type: Informational
Version: 0.1
Last Updated: 2011-04-11
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

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.

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".

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 - 2011 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status:	Experimental
Type:	Informational
Version:	0.1
Last Updated:	2011-04-11