Network Working Group M. Mealling Internet-Draft VeriSign, Inc. Expires: December 28, 2002 June 29, 2002 The IETF XML Registry draft-mealling-iana-xmlns-registry-04.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 28, 2002. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract 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. Mealling Expires December 28, 2002 [Page 1] Internet-Draft The IETF XML Registry June 2002 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 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 that follows [RFCXXXX]. 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: urn:ietf:params:xml:: will be assigned where is the type of the document being registered (see below). 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 Mealling Expires December 28, 2002 [Page 2] Internet-Draft The IETF XML Registry June 2002 registered elements are available via http://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 and the individual files have the 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 identifiers. 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 [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." Mealling Expires December 28, 2002 [Page 3] Internet-Draft The IETF XML Registry June 2002 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:'. 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: 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:'. 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: 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 Mealling Expires December 28, 2002 [Page 4] Internet-Draft The IETF XML Registry June 2002 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. XML 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 repository. 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, 1986. Mealling Expires December 28, 2002 [Page 5] Internet-Draft The IETF XML Registry June 2002 [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, . Author's Address Michael Mealling VeriSign, Inc. Mountain View, CA US URI: http://www.research.netsol.com Mealling Expires December 28, 2002 [Page 6] Internet-Draft The IETF XML Registry June 2002 Full Copyright Statement Copyright (C) The Internet Society (2002). 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. 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Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Mealling Expires December 28, 2002 [Page 7]