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Network Working Group                                        M. MeallingRequest for Comments: 3688                                VeriSign, Inc.BCP: 81                                                     January 2004Category: Best Current PracticeThe IETF XML RegistryStatus of this Memo   This document specifies an Internet Best Current Practices for the   Internet Community, and requests discussion and suggestions for   improvements.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2004).  All Rights Reserved.Abstract   This document describes an IANA maintained registry for IETF   standards which use Extensible Markup Language (XML) related items   such as Namespaces, Document Type Declarations (DTDs), Schemas, and   Resource Description Framework (RDF) Schemas.1.  Introduction   Over the past few years, the Extensible Markup Language (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 Document Type Definitions (DTDs), XML   Namespaces [W3C.REC-xml-names], and XML Schemas [W3C.REC-xmlschema-   1]. Each one of these technologies uses Uniform Resource Identifiers   (URIs) [RFC2396] and other standardized identifiers to identify   various components.   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 andMealling                 Best Current Practice                  [Page 1]

RFC 3688                 The IETF XML Registry              January 2004   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      registration,   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 (URN) that follows   [RFC3553].2.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inBCP 14,RFC 2119   [RFC2119].3.  Registerable Documents3.1.  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      urn:ietf:params:xml:<class>:<id>   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   consensus process.  Basically, this means that it must be documented   in a RFC.  TheRFC 3553 [RFC3553] URN registration template is found   inSection 6.   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   registered elements are available viahttp://www.iana.org/assignments/.  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.Mealling                 Best Current Practice                  [Page 2]

RFC 3688                 The IETF XML Registry              January 2004   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 when to   not reference IANA network resources as a 'schema download   repository'.  This is the reason that the IANA will not register or   provide SYSTEM identifiers.3.2.  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.  However, 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 and      understood to not cause any unacceptable harm.      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 Identifiers      [ISO.8879.1986] but they are not restricted to just that set.  As      said in [RFC3151]:         "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."      Therefore, it is legal for a PUBLIC identifier to be a URN if it      adheres to the character set restrictions.Mealling                 Best Current Practice                  [Page 3]

RFC 3688                 The IETF XML Registry              January 2004      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      name.   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      'urn:ietf:params:xml:schema:<id>'.   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      'urn:ietf:params:xml:rdfschema:<id>'.4.  Registration Procedures   Until the IANA requests or implements an automated process for the   registration of these elements, any specifications 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:   URI      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      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.Mealling                 Best Current Practice                  [Page 4]

RFC 3688                 The IETF XML Registry              January 2004   XML      The exact XML to be stored in the registry.  Unless the beginning      and end of the file is obvious, 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 repository.5.  Security Considerations   The information maintained by the IANA will be authoritative and will   be a target for attack.  In some cases, such as XML Schema and DTDs,   the content maintained by the IANA may be directly input into   software.  Thus, extra care should be taken by the IANA to maintain   the security precautions required for an important reference location   for the Internet.   Beyond this concern, there are no other security considerations not   already found with any other IANA registry.6.  IANA Considerations   This document 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 a Specification is Required.  Once the IETF   has some experience with this registry, these policies may change.RFC 3553 [RFC3553] specifies that any new registry requiring a name,   to be assigned below the 'urn:ietf:params' namespace and must specify   the structure of that space in template form.  The IANA has created   and will 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      <id>.   Repository: To be assigned according to the guidelines found above.   Index value: The class nameMealling                 Best Current Practice                  [Page 5]

RFC 3688                 The IETF XML Registry              January 20047.  Normative References   [ISO.8879.1986]       International Organization for Standardization,                         "Information processing - Text and office                         systems - Standard generalized markup language                         (SGML)", ISO Standard 8879, 1986.   [RFC2119]             Bradner, S., "Key words for use in RFCs to                         Indicate Requirement Levels",BCP 14,RFC 2119,                         March 1997.   [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.   [RFC3553]             Mealling, M., Masinter, L., Hardie, T. and G.                         Klyne, "An IETF URN Sub-namespace for                         Registered Protocol Parameters",BCP 73,RFC3553, June 2003.   [W3C.CR-rdf-schema]   Brickley, D. and R. Guha, "Resource Description                         Framework (RDF) Schema Specification 1.0", W3C                         CR-rdf-schema, March 2000,                         <http://www.w3.org/TR/2000/CR-rdf-schema-20000327>.   [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,                         <http://www.w3.org/TR/REC-xml>.   [W3C.REC-xml-names]   Bray, T., Hollander, D. and A. Layman,                         "Namespaces in XML", W3C REC-xml-names, January                         1999, <http://www.w3.org/TR/REC-xml-names>.   [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://www.w3.org/TR/xmlschema-1/>.Mealling                 Best Current Practice                  [Page 6]

RFC 3688                 The IETF XML Registry              January 20048.  Intellectual Property Statement   The IETF takes no position regarding the validity or scope of any   intellectual property or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; neither does it represent that it   has made any effort to identify any such rights.  Information on the   IETF's procedures with respect to rights in standards-track and   standards-related documentation can be found inBCP-11.  Copies of   claims of rights made available for publication and any assurances of   licenses to be made available, or the result of an attempt made to   obtain a general license or permission for the use of such   proprietary rights by implementors or users of this specification can   be obtained from the IETF Secretariat.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights which may cover technology that may be required to practice   this standard.  Please address the information to the IETF Executive   Director.9.  Author's Address   Michael Mealling   VeriSign, Inc.   Mountain View, CA   USA   EMail: michael@verisignlabs.com   URI:http://www.research.verisignlabs.comMealling                 Best Current Practice                  [Page 7]

RFC 3688                 The IETF XML Registry              January 200410.  Full Copyright Statement   Copyright (C) The Internet Society (2004).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assignees.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Mealling                 Best Current Practice                  [Page 8]