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Network Working Group                                         S. Leonard
Internet-Draft                                             Penango, Inc.
Intended status: Standards Track                      September 24, 2015
Expires: March 27, 2016


             URN Namespaces for XML Namespaces and RDF IRIs
                    draft-seantek-xmlns-rdf-urns-01

Abstract

   XML segregates elements into namespaces, which can be used to mix
   tags with different semantics in a composite XML document.  XML
   namespaces are identified by URIs (XML 1.0) or IRIs (XML 1.1).
   Similarly, RDF contains "nodes" that are identified by "URI
   references" (RDF 1.0) or "IRIs" (RDF 1.1).  This document defines
   URNs specifically for XML namespaces and RDF nodes.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 27, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   XML segregates elements into namespaces, which can be used to mix
   tags with different semantics in a composite XML document.  XML
   namespaces are identified by URIs [XML1.0] or IRIs [XML1.1].
   Similarly, RDF identifies nodes by "URI reference" [RDF1.0] or "IRI"
   [RDF1.1].  This document defines URN namespace identifiers (NIDs)
   specifically for identifying XML namespaces and RDF nodes.

   Experience suggests that several URN namespace registrations have
   been proposed over the years, where the primary (yet only
   occasionally stated) purpose is to create concise, targeted resource
   identifiers for XML or RDF use.  An designer now has the option of
   choosing a concise, mnemonic identifier without the cost of
   maintaining and relying upon a long-lived network location (such as
   an HTTP URL), and without the hassle of registering a URN namespace
   identifier via IETF Consensus.  One exemplary advantage of using an
   xmlns URN over an HTTP URL is that even if the organization hosting
   the original XML schema ceases to exist, the URI will remain
   functional without needing to commandeer back an embedded domain
   name.

   A name in the urn:xmlns namespace uniquely and persistently
   identifies an abstract XML namespace resource.  The abstract resource
   does not have any particular concrete representation (such as a type
   of content identified by Internet media type), although concrete
   representations (referenced by URIs) may be associated with it as
   discussed in Section 4.  Abstract parts of the abstract resource can
   be identified with fragment identifiers.

   A name in the urn:rdf namespace uniquely and persistently identifies
   an abstract RDF node resource ("URI reference" per [RDF1.0], or "IRI"
   per [RDF1.1]).  The abstract resource does not have any particular
   concrete representation (such as a type of content identified by
   Internet media type), although concrete representations (referenced
   by URIs) may be associated with it.  Abstract parts of the abstract
   resource can be identified with fragment identifiers.

   Two distinct namespaces are valuable because each namespace
   represents a different abstract resource type, which can have type-
   specific concrete representations.  For example,
   "urn:xmlns:foobar2015" could represent some foobar2015 XML namespace,
   with associated XML schema definitions.  In contrast,
   "urn:rdf:foobar2015" could represent some RDF node (or some RDF node
   prefix), with associated description resources.



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1.1.  Definitions

   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 in RFC 2119.

   The term "divider" means a punctuation character such as colon ":"
   that serves to divide a name into parts.

   The term "part" means the characters between divisions (dividers or
   the ends of the name).

   While a name "divided" into "parts" can be seen as forming a tree or
   hierarchy, names in this specification are not hierarchical in the
   [RFC3986] sense, and have no hierarchical semantic content.  Names
   SHOULD be treated as opaque identifiers that are only compared for
   equality.

   The term "initial prefix" means the first part of a name.

   The term "DIGIT" is from the ABNF production in [RFC5234], i.e., the
   US-ASCII characters 0 through 9.

2.  Registration Template for xmlns NID

 Namespace ID:
    xmlns

 Registration Information:
    Version: 1
    Date: 2015-09-24

 Declared registrant of the namespace:
    IETF

 Declaration of syntactic structures:
    An xmlns name is any
    valid XML name corresponding to "Name" in Section 2.3
    of [XML1.0] (production 5), with the following restrictions:
       1. The name MUST be at least four characters.
       2. Colons MAY be used as intra-name dividers.
       3. Colons MUST NOT appear at the beginning or end of the name.
       4. Consecutive colons MUST NOT appear.
    and the following relaxation:
       5. The first part of the name preceding the first colon MAY
          be comprised of DIGITs (which are intended to correspond
          to registered IANA Private Enterprise Numbers);
          further discussion is in



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          "Process of identifier assignment".

      The ABNF of a name is:

       urn-xmlns-name = [DIGIT+ ":"] NoColonNameStartChar
                        *([":"] NoColonNameChar)

    Where the productions NoColonNameStartChar and NoColonNameChar
    are respectively taken from NameStartChar (production 4)
    and NameChar (production 4a) in [XML1.0], with ":" omitted.
    Although ABNF is formally US-ASCII only, the domain of
    this production includes the whole Unicode range.

    The name is used as the basis of the
    Namespace Specific String (NSS) as follows.
    When the NSS is encoded in a URN in a URI protocol slot,
    Unicode code points beyond U+007F
    are encoded as percent-encoded UTF-8. Conveniently,
    all XML name characters in the US-ASCII range are in the
    [RFC3986] unreserved set.
    When the NSS is encoded in a URN in a IRI protocol slot,
    Unicode code points beyond U+007F in the unreserved set
    are encoded as-is; they MUST NOT be percent-encoded.

 Relevant ancillary documentation:
    [XML1.0], [XML1.1].

 Identifier uniqueness considerations:
    The meaning of an identifier is registered in the registry,
    and thus is unique.

 Identifier persistence considerations:
    Once an identifier is registered, its meaning cannot be changed.

 Process of identifier assignment:
    Identifiers are registered with IANA on a First-Come, First-Served
    basis. One-character initial prefixes are reserved for further
    use. Two- and three-character initial prefixes are intended to
    correlate with language tags and regional codes; however, they
    have no such semantic content when used in an xmlns name. Whole
    number initial prefixes are intended to represent IANA
    Private Enterprise Numbers.
    Registrants are free to register names with reserved two-character
    and three-character initial prefixes, such as "au:flag" or
    "en:us:ca:lax". Registrants are also free to register names with
    whole number prefixes, such as "20:10-250": these names have a
    particular registration process since they implicitly relate
    relate to IANA Private Enterprise Numbers.



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    The IANA Considerations section fully defines the
    registration processes.

 Process for identifier resolution:
    The registration for a particular identifier MAY include
    any number of URIs that a URN resolver MAY use to resolve
    the URN to return specific resources. The registered
    URIs are not equivalent to the registered URN, so an XML document
    that refers to that particular namespace MUST use the registered
    URN as the XML namespace URI. IANA will maintain the resolution
    database--see Section 4.
    A URN resolver SHALL pass any [RFC3986] fragment component in the
    urn: URI or IRI through to the resolved URI if the registered URI
    does not have a fragment component. See [URNBIS].
    If the registered URI has a fragment component, a URN resolver
    SHALL NOT pass any [RFC3986] fragment component in the urn: URI
    or IRI; the fragment component SHALL be ignored.

 Rules for Lexical Equivalence:
    The NSS is compared case sensitively.
    If a URI and a IRI are compared against each other, the
    UTF-8 percent-encoded octets in the URI representing code points
    in the unreserved set beyond U+007F SHALL be treated
    as the Unicode code points
    in the IRI. An IRI that contains UTF-8 percent-encoded octets
    in the unreserved set beyond U+007F is not supposed to exist;
    it is a protocol error.
    Fragments (delimited by the # character) are not considered
    part of the name, the NSS, or the URN, so a fragment would not
    affect lexical equivalence. Nevertheless, a urn: URI or IRI
    might be produced with a fragment component.

 Conformance with URN Syntax:
    The URN of this namespace conforms to new URN Syntax
    [URNBIS], old URN syntax [RFC2141], and Uniform Resource Identifier
    (URI): Generic Syntax [RFC3986].

 Validation mechanism:
    An XMLNS URN may be validated by looking it up in the IANA Registry.

 Scope:
    Global.

3.  Registration Template for rdf NID







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   Namespace ID:
      rdf

   Registration Information:
      Version: 1
      Date: 2015-09-24

   [[TODO: paste xmlns content and make rdf substitutions.]]

   Scope:
      Global.

4.  IANA Considerations

   This document requests the assignment of formal URN namespace IDs
   "xmlns" and "rdf".

   This document requests the creation of an IANA registry called
   "urn:xmlns Names", and an IANA registry called "urn:rdf Names".  The
   registries are First-Come, First-Served [RFC5226].  Each registration
   shall contain:

   a.  the name conforming to this document

       1)  in Unicode characters and

       2)  with characters beyond U+007F percent-encoded in UTF-8,

   b.  an optional description,

   c.  optional [RFC3986] conforming URIs that are not URNs that are to
       be used for URN resolution, and

   d.  contact information for the registrant.

   After submitting a new registration, the registration SHALL be
   effective and entered into the registry after 120 hours (5 days).
   Registrants or their successors may update their entries from time to
   time.  After submitting an updated registration, the registration
   SHALL be effective and entered into the registry after 48 hours (2
   days).  During the waiting period, a registrant MAY withdraw the
   proposed registration for any reason.

   The registration template SHALL be encoded in UTF-8.

   If a registrant attempts to register a name that is confusingly
   similar to other registered names (such as only differing by case, or
   differing by code points but generating the same or confusingly



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   similar visual representations), the registrants of the prior names
   are to receive a warning notification of the registration.  IANA
   SHOULD implement a modern algorithm to detect such confusingly
   similar names.

   If a registrant attempts to register a name that contains a whole
   number initial prefix, the number MUST correspond to an existing IANA
   Private Enterprise Number.  The registrant of the corresponding IANA
   Private Enterprise Number is to receive a notification of the
   impending registration.  The PEN registrant MAY veto the impending
   registration during this time.  Otherwise, the registration will
   succeed.

   IANA is to maintain these registries at designated URIs on its
   website, currently www.iana.org.  Regardless of other formatting,
   IANA will designate URIs of the form: {pre}/{name}, where {pre} is
   IANA's chosen name registry prefix over HTTP or HTTPS, and {name} is
   the name (with UTF-8 percent-encoding).  The response to an HTTP GET
   request at one of these URIs SHALL be a text/plain document with
   UTF-8 encoding ("charset=UTF-8") formatted as follows:

   urn:{xmlns or rdf}:{name}
   Description: {description}
   Contact Information: {contact information}

   {URI 0}
   {URI 1}
   {...}

   The Description and Contact Information fields MAY span multiple
   lines by ending the line and including one space (U+0020) on the
   subsequent line.  Semantically, the line-ending and space mean "end
   of line" only.  URN resolvers MAY use this database (whether IANA's
   customary form, or the form specified by this section) when resolving
   URNs to URIs to access particular resources.

   The purpose of these registered URIs is to assist protocol designers,
   systems analysts, and software engineers with understanding the
   nature of the XML namespace or RDF node, rather than for general
   consumption.  For example, one registered URI could forward to a
   text/html resource that is a standards document describing a protocol
   that uses the URN.  [[NB: compare with xml.resource.org for I-Ds.]]
   Consequently, the traffic burden imposed on IANA is expected to be
   negligible.







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5.  Security Considerations

   XML processors use XML namespaces to validate XML content.  This
   document is not expected to introduce any additional security
   considerations beyond those inherent in XML processing.

   RDF processors use RDF URI references (RDF 1.0) or IRIs (RDF 1.1) to
   identify nodes (subjects, predicates, and objects).  This document is
   not expected to introduce any additional security considerations
   beyond those inherent in RDF processing.

6.  References

6.1.  Normative References

   [RDF1.0]   Klyne, G. and J. Carroll, "Resource Description Framework
              (RDF): Concepts and Abstract Syntax", World Wide Web
              Consortium Recommendation REC-rdf-concepts-20040210,
              February 2004,
              <http://www.w3.org/TR/2004/REC-rdf-concepts-20040210>.

   [RDF1.1]   Cyganiak, R., Wood, D., and M. Lanthaler, "RDF 1.1
              Concepts and Abstract Syntax", World Wide Web Consortium
              Recommendation REC-rdf11-concepts-20140225, February 2014,
              <http://www.w3.org/TR/2014/REC-rdf11-concepts-20140225/>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [URNBIS]   Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", draft-ietf-urnbis-rfc2141bis-urn-13 (work in
              progress), September 2015.






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   [XML1.0]   Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <http://www.w3.org/TR/2008/REC-xml-20081126>.

   [XML1.1]   Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E.,
              Yergeau, F., and J. Cowan, "Extensible Markup Language
              (XML) 1.1 (Second Edition)", World Wide Web Consortium
              Recommendation REC-xml11-20060816, August 2006,
              <http://www.w3.org/TR/2006/REC-xml11-20060816>.

6.2.  Informative References

   [RFC2276]  Sollins, K., "Architectural Principles of Uniform Resource
              Name Resolution", RFC 2276, January 1998.

Author's Address

   Sean Leonard
   Penango, Inc.
   5900 Wilshire Boulevard
   21st Floor
   Los Angeles, CA  90036
   USA

   Email: dev+ietf@seantek.com
   URI:   http://www.penango.com/























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