Network Working Group                                        M. Mealling
Internet-Draft                                            VeriSign, Inc.
Expires: December 28, 2002                                 June 29, 2002

                         The IETF XML Registry

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Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.


   This document describes an IANA maintained registry for IETF
   standards which use XML related items such as Namespaces, DTD,
   Schemas, and RDF Schemas.

1. Introduction

   Over the past few years XML [W3C.REC-xml] has become a widely used
   method for data markup.  There have already been several IETF Working
   Groups that have produced standards that define XML DTDs, XML
   Namespaces [W3C.REC-xml-names] and XML Schemas [W3C.REC-xmlschema-1].
   Each one of these technologies uses URIs [RFC2396] and other
   standardized identifiers to identify various components.

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   For example, while it has been the practice within some standards
   that use Document Type Definitions (DTDs) to forego the use of the
   PUBLIC identifiers in favor of 'well known' SYSTEM identifiers, it
   has proven to be more trouble than its worth to attempt to
   standardize SYSTEM identifiers.  The result is that several IETF
   standards that have simply created non-resolvable URIs in order to
   simply identify but not resolve the DTD for some given XML document.

   This document seeks to standardize and improve these practices by
   creating an IANA maintained registry of XML element identifiers so
   that document authors and implementors have a well maintained and
   authoritative location for their XML elements.  As part of this
   standard, the IANA will maintain

   o  the public representation of the document,

   o  the URI for the elements if one is provided at the time of

   o  a registry of Public Identifiers as URIs.

   In the case where the registrant does not request a particular URI,
   the IANA will assign it a Uniform Resource Name that follows

2. Registerable Documents

2.1 The Assigned/Registered URI

   All elements (except PUBLIC identifiers) in this registry will
   require a URI in order to be registered.  If the registrant wishes to
   have a URI assigned  then a URN of the form:


    will be assigned where <class> is the type of the document being
   registered (see below).  <id> is a unique id generated by the IANA
   based on any means the IANA deems necessary to maintain uniqueness
   and persistence.  NOTE: in order for a URN of this type to be
   assigned, the item being registered MUST have been through the IETF
   concensus process.  Practically this means it must be documented in
   an RFC.  The RFC XXXX [RFCXXXX] URN registration template is found in
   Section 4.

   The IANA will also maintain a file server available via at least HTTP
   and FTP that contains all of the registered elements in some publicly
   accessible file space in the same way that all of the IANA's

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   registered elements are available via  While the directory structure of
   this server is up to the IANA, it is suggested that the files be
   organized by the <class> and the individual files have the <id> as
   their filename.

   Implementors are warned that they should not programatically rely on
   those resources being available or the directory structure remaining
   static for any reason.  It is explicitly recognized that some
   software tools attempt to download DTDs, schema, etc 'on the fly' and
   that developers should understand when this is done and to not
   reference IANA network resources as a 'schema download repository'.
   This is the reason that the IANA will not register or provide SYSTEM

2.2 Registerable Classes

   The list of types of XML elements that can be registered with the
   IANA are:

   publicid -- An XML document that contains a DOCTYPE declaration or
      any other external reference can identify that reference via both
      a PUBLIC identifier and a SYSTEM identifier.  The SYSTEM
      identifier is system-specific information that enables the entity
      manager of an XML system to locate the file, memory location, or
      pointer within a file where the entity can be found.  It should
      also be noted that a system identifier could be an invocation of a
      program that controls access to an entity that is being
      identified.  Thus they are not registered items.  In many cases,
      SYSTEM identifiers are also URIs but in these cases the URI is
      still only used for system-specific information.  In the case
      where a PUBLIC Identifier is also a URI it is possible for the
      SYSTEM Identifier to contain the same URI but this behavior is not
      recommended unless its side effects are well known.

      A PUBLIC identifier is a name that is intended to be meaningful
      across systems and different user environments.  Typically it will
      be a name that has a registered owner associated with it, so that
      public identifiers will be guaranteed unique and no two entities
      will have the same public identifier.  In practice, PUBLIC
      identifiers are typically Formal Public Identifers [ISO.8879.1986]
      but they are not restricted to just that set.  As said in

         "Any string which consists only of the public identifier
         characters (defined by Production 13 of Extensible Markup
         Language (XML) 1.0 Second Edition) is a legal public identifier."

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       Therefore it is legal for a PUBLIC identifier to be a URN if it
      adheres to the character set restrictions.

      Thus, the identifier registered along with a DTD is its PUBLIC
      identifier.  The only restriction being that it must adhere to the
      character set restrictions.  In the case where the registrant does
      not provide one, the IANA will assign one of the form
      'urn:ietf:params:xml:pi:<id>'.  Registrants are encouraged to
      investigate RFC  3151 [RFC3151] as a recommended method for
      minting a URN that can also be represented as an FPI.

   ns -- XML Namespaces [W3C.REC-xml-names] are named by a URI.  They
      have no real, machine-parseable representation.  Thus the
      registered document will be either the specification or a
      reference to it.  In the case where a URI is not provided by the
      registrant, the IANA will assign a URN of the form
      'urn:ietf:params:xml:ns:<id> which will be the XML Namespace's

   schema -- XML Schemas [W3C.REC-xmlschema-1] are also identified by a
      URI but their contents are machine parseable.  The IANA registered
      document will be the XML Schema file.  The URN the IANA assigns
      can be used as the URI for the schema and is of the form

   rdfschema -- The Resource Description Format (RDF) [W3C.CR-rdf-
      schema] is an XML serialization of a connected graph based data
      model used for metadata expression.  RDF makes use of schemas for
      RDF that express grammars about relationships between URIs.  These
      grammars are identified by URIs.  The URN assigned by the IANA can
      be used as the identifying URI and is of the form

3. Registration Procedures

   Until such time as the IANA requests or implements an automated
   process for the registration of these elements, any specifications
   wishing to do so must make that request part of the IANA
   considerations section of their respective documents.  That request
   must be in the form of the following template:

      The URI or PUBLIC identifier that identifies the XML component.
      If the registrant is requesting that the IANA assign a URI then
      this field should be specified as "please assign"

   Registrant Contact

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      The individual/organization that is the registration contact for
      the component being registered.  Ideally this will be the name and
      pertinent physical and network contact information.  In the case
      of IETF developed standards the Registrant will be the IESG.

      The exact XML to be stored in the registry.  Unless otherwise
      obvious what the beginning and end of the file are, the document
      should use the text "BEGIN" to mark the beginning of the file and
      "END" to mark the end of the file.  The IANA will insert any text
      between those two strings (minus any page breaks and RFC
      formatting inserted by the RFC Editor) into the file kept in the

4. IANA Considerations

   This documents seeks to create a rather large registry for which the
   IANA (at the direction of the IESG) will be primarily responsible.
   The amount of effort required to maintain this registry is not
   insignificant and the policies and procedures surrounding any
   approval process are non-trivial.  The registry is on a First Come
   First Served basis but at this time a Specification is Required.
   Once the IETF has some experience with this registry these policies
   may change.

   RFC XXXX [RFCXXXX] specifies that any new registry that requires a
   name to be assigned below the 'urn:ietf:params' namespace must
   specify the structure of that space in template form.  The IANA is
   directed to create and maintain this new sub-namespace:

   Registry-name: xml

   Specification: This document contains the registry specification.
      The namespace is organized with one sub-namespace which is the

   Repository: To be assigned according to the guidelines found above.

   Index value: The class name

Normative References

   [ISO.8879.1986]        International Organization for
                          Standardization, "Information processing -
                          Text and office systems - Standard generalized
                          markup language (SGML)", ISO Standard 8879,

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   [RFC2396]              Berners-Lee, T., Fielding, R. and L. Masinter,
                          "Uniform Resource Identifiers (URI): Generic
                          Syntax", RFC 2396, August 1998.

   [RFC3151]              Walsh, N., Cowan, J. and P. Grosso, "A URN
                          Namespace for Public Identifiers", RFC 3151,
                          August 2001.

   [RFCXXXX]              Mealling, M., Masinter, L., Hardie, T. and G.
                          Klyne, "An IETF URN Sub-namespace for
                          Registered Protocol Parameters", draft-
                          mealling-iana-urn-02.txt (work in progress),
                          August 2001.

   [W3C.CR-rdf-schema]    Brickley, D. and R. Guha, "Resource
                          Description Framework (RDF) Schema
                          Specification 1.0", W3C CR-rdf-schema, March
                          2000, <

   [W3C.REC-xml]          Bray, T., Paoli, J., Sperberg-McQueen, C. and
                          E. Maler, "Extensible Markup Language (XML)
                          1.0 (2nd ed)", W3C REC-xml, October 2000,

   [W3C.REC-xml-names]    Bray, T., Hollander, D. and A. Layman,
                          "Namespaces in XML", W3C REC-xml-names,
                          January 1999, <

   [W3C.REC-xmlschema-1]  Thompson, H., Beech, D., Maloney, M. and N.
                          Mendelsohn, "XML Schema Part 1: Structures",
                          W3C REC-xmlschema-1, May 2001, <http://

Author's Address

   Michael Mealling
   VeriSign, Inc.

   Mountain View, CA


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