XEP-0328: JID Prep

This specification defines a way for an XMPP client to request an XMPP server to prep and normalize a given JID.
Lance Stout
© 1999 – 2019 XMPP Standards Foundation. SEE LEGAL NOTICES.


WARNING: This document has been automatically Deferred after 12 months of inactivity in its previous Experimental state. Implementation of the protocol described herein is not recommended for production systems. However, exploratory implementations are encouraged to resume the standards process.
Standards Track
0.1 (2013-05-28)
Document Lifecycle
  1. Experimental
  2. Deferred
  3. Proposed
  4. Draft
  5. Final

1. Introduction

In order to properly compare and match JIDs, a normalization and prepping step is required by RFC 6122 [1]. The responsibility for such normalization is split between the server and client, where the server is expected to prep any JID slots that it recognizes, particulary those related to stanza routing and roster items. However, the server can not prep JID slots that it does not understand, and so those are left for the client to process.

In some environments (in particular, browser based environments), a client does not have access to the various Unicode and internationalization libraries necessary to properly prep and normalize a JID. For those situations, this protocol defines a way for a client to ask a server to normalize a JID on its behalf.

2. Discovering support

If a server supports JID prep queries, it MUST specify the 'urn:xmpp:jidprep:0' feature in its service discovery information features as specified in Service Discovery (XEP-0030) [2] and the Entity Capabilities profile specified in Entity Capabilities (XEP-0115) [3].

Example 1. Client checks for support by the server
<iq type="get"
  <query xmlns="http://jabber.org/protocol/disco#info"/>
Example 2. Server advertises support for JID prep queries
<iq type="result"
  <query xmlns="http://jabber.org/protocol/disco#info">
    <feature var="urn:xmpp:jidprep:0"/>

The JID prep service MAY be supported through the use of an external component (Jabber Component Protocol (XEP-0114) [4]); in which case, the component MUST return an identity of "component/jidprep" in addition to the "urn:xmpp:jidprep:0" feature.

Example 3. Server component advertises support for JID prep queries
<iq type="result"
  <query xmlns="http://jabber.org/protocol/disco#info">
    <identity category="component" type="jidprep" />
    <feature var="urn:xmpp:jidprep:0" />

3. Use Cases

In order to request prepping for a JID, the client sends an <iq/> stanza of type "get" to the server, containing a <jid/> element qualified by the 'urn:xmpp:jidprep:0' namespace and whose XML character data is the JID in question:

Example 4. Client requests the server to prep and normalize a JID
<iq type="get"
  <jid xmlns="urn:xmpp:jidprep:0">ROMeo@montague.lit/orchard</jid>

The server MUST return either an IQ-result or an IQ-error. When returning an IQ-result, the server sends an <iq/> staza of type='result' containing a <jid/> element qualifed by the 'urn:xmpp:jidprep:0' namespace and whose XML character data MUST be the prepped and normalized version of the requested JID:

Example 5. Server responds with the prepped JID
<iq type="result"
  <jid xmlns="urn:xmpp:jidprep:0">romeo@montague.lit/orchard</jid>

If an IQ-error is returned, then it SHOULD specify an error condition of <jid-malformed/> if the given JID could not be processed to a normalized form:

Example 6. Server responds with an error for an invalid JID
<iq type="error"
  <jid xmlns="urn:xmpp:jidprep:0">romeo@@montague.lit/orchard</jid>
  <error type="modify">
    <jid-malformed xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" />

4. Implementation Notes

If a client has the ability to perform the prepping and normalization process itself, it SHOULD NOT make a JID prep request to the server.

Upon a successful response, the client SHOULD cache the result, mapping the original JID to the normalized version.

In order to reduce the number of queries made by clients, the server MUST enforce normalization rules for any JID slots understood by the server (e.g. the to and from attributes, roster item JIDs, etc). [5]

5. Security Considerations

As the process for normalizing a JID can be resource intensive, there is a possibility for denial of service attacks. A server MAY rate limit the number of requests to prevent such attacks. Likewise, the server MAY only respond to requests from users that are local to the server.

6. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [7].

7. XMPP Registrar Considerations

7.1 Protocol Namespaces

The XMPP Registrar [8] includes 'urn:xmpp:jidprep:0' in its registry of protocol namespaces (see <https://xmpp.org/registrar/namespaces.html>).

7.2 Protocol Versioning

If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.

7.3 Service Discovery Category/Type

The XMPP Registrar [8] includes a category of "component" in its registry of Service Discovery identities (see <https://xmpp.org/registrar/disco-categories.html>); as a result of this document, the Registrar includes a type of "jidprep" to that category.

The registry submission is as follows:

          A server component that offers a JID prepping
          and normalization service to constrained clients.

8. XML Schema

<?xml version='1.0' encoding='UTF-8'?>


      The protocol documented by this schema is defined in
      XEP-xxxx: http://www.xmpp.org/extensions/xep-xxxx.html

  <xs:element name='jid'>
      <xs:simpleContent />



Appendix A: Document Information

XMPP Standards Foundation
Standards Track
Last Updated
Approving Body
XMPP Council
XMPP Core, XMPP IM, XEP-0030
Superseded By
Short Name
Source Control

This document in other formats: XML  PDF

Appendix B: Author Information

Lance Stout


This XMPP Extension Protocol is copyright © 1999 – 2018 by the XMPP Standards Foundation (XSF).


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 <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

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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 6122: Extensible Messaging and Presence Protocol (XMPP): Address Format <http://tools.ietf.org/html/rfc6122>.

2. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.

3. XEP-0115: Entity Capabilities <https://xmpp.org/extensions/xep-0115.html>.

4. XEP-0114: Jabber Component Protocol <https://xmpp.org/extensions/xep-0114.html>.

5. This requirement is intended to be subsumed by the requirements introduced in rfc6122bis [6]

6. Extensible Messaging and Presence Protocol (XMPP): Address Format <https://datatracker.ietf.org/doc/draft-ietf-xmpp-6122bis/>. Work in progress.

7. 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/>.

8. 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 <https://xmpp.org/registrar/>.

Appendix H: Revision History

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

  1. Version 0.1 (2013-05-28)

    Initial published version approved by the XMPP Council.

  2. Version 0.0.2 (2013-05-21)

    Incorporated feedback.

  3. Version 0.0.1 (2013-05-08)

    Initial version.