Uniform Resource Names (URNs)
draft-ietf-urnbis-rfc2141bis-urn-12
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8141.
|
|
|---|---|---|---|
| Authors | Peter Saint-Andre , Dr. John C. Klensin | ||
| Last updated | 2015-06-15 | ||
| Replaces | draft-ah-rfc2141bis-urn, draft-saintandre-urnbis-2141bis, draft-ietf-urnbis-rfc3406bis-urn-ns-reg | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 8141 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-urnbis-rfc2141bis-urn-12
URNBIS P. Saint-Andre
Internet-Draft &yet
Obsoletes: 2141, 3406 (if approved) J. Klensin
Intended status: Standards Track
Expires: December 17, 2015 June 15, 2015
Uniform Resource Names (URNs)
draft-ietf-urnbis-rfc2141bis-urn-12
Abstract
A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI)
that is assigned under the "urn" scheme and a particular URN
namespace, with the intent that the URN will be either a persistent,
location-independent resource identifier or in some cases an abstract
designator that is persistent but that does not identify a resource.
With regard to URN syntax, this document defines the canonical syntax
for URNs (in a way that is consistent with URI syntax), specifies
methods for determining URN equivalence, and discusses URI
conformance. With regard to URN namespaces, this document specifies
a method for defining a URN namespace and associating it with a
namespace identifier, and describes procedures for registering
namespace identifiers with the Internet Assigned Numbers Authority
(IANA). This document obsoletes both RFC 2141 and RFC 3406.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on December 17, 2015.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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than English.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. URN Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Namespace Identifier . . . . . . . . . . . . . . . . . . 6
3.2. Namespace Specific String . . . . . . . . . . . . . . . . 6
3.3. Optional Components . . . . . . . . . . . . . . . . . . . 7
4. Equivalence of URNs . . . . . . . . . . . . . . . . . . . . . 9
4.1. Procedure . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10
5. URI Conformance . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Use in URI Protocol Slots . . . . . . . . . . . . . . . . 11
5.2. Parsing . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.3. URNs and Relative References . . . . . . . . . . . . . . 12
5.4. Transport and Display . . . . . . . . . . . . . . . . . . 13
5.5. URI Design and Ownership . . . . . . . . . . . . . . . . 13
6. URN Namespaces . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Formal Namespaces . . . . . . . . . . . . . . . . . . . . 15
6.2. Informal Namespaces . . . . . . . . . . . . . . . . . . . 17
7. Defining and Registering a URN Namespace . . . . . . . . . . 17
7.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 17
7.2. Registration Policy and Process . . . . . . . . . . . . . 18
7.3. Completing the Template . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
8.1. URI Scheme . . . . . . . . . . . . . . . . . . . . . . . 22
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8.2. Registration of URN Namespaces . . . . . . . . . . . . . 23
9. Security and Privacy Considerations . . . . . . . . . . . . . 23
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.1. Normative References . . . . . . . . . . . . . . . . . . 23
10.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. Registration Template . . . . . . . . . . . . . . . 26
A.1. Namespace ID . . . . . . . . . . . . . . . . . . . . . . 26
A.2. Version . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.3. Date . . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.4. Registrant . . . . . . . . . . . . . . . . . . . . . . . 26
A.5. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.6. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.7. Assignment . . . . . . . . . . . . . . . . . . . . . . . 27
A.8. Security and Privacy . . . . . . . . . . . . . . . . . . 27
A.9. Interoperability . . . . . . . . . . . . . . . . . . . . 27
A.10. Resolution . . . . . . . . . . . . . . . . . . . . . . . 27
A.11. Documentation . . . . . . . . . . . . . . . . . . . . . . 27
A.12. Revision Information . . . . . . . . . . . . . . . . . . 27
Appendix B. Changes from RFC 2141 . . . . . . . . . . . . . . . 27
Appendix C. Changes from RFC 3406 . . . . . . . . . . . . . . . 27
Appendix D. Contributors . . . . . . . . . . . . . . . . . . . . 28
Appendix E. Acknowledgements . . . . . . . . . . . . . . . . . . 28
Appendix F. Change log for versions of draft-ietf-urnbis-
rfc2141bis-urn . . . . . . . . . . . . . . . . . . . 28
F.1. Changes from -08 to -09 . . . . . . . . . . . . . . . . . 28
F.2. Changes from -09 to -10 . . . . . . . . . . . . . . . . . 29
F.3. Changes from -10 to -11 . . . . . . . . . . . . . . . . . 29
F.4. Changes from -11 to -12 . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI)
[RFC3986] that is assigned under the "urn" scheme and a particular
namespace, with the intent that the URN will be either a persistent,
location-independent resource identifier or in some cases an abstract
designator that is persistent but that does not identify a resource.
A URN namespace is a collection of such identifiers, each of which is
(1) unique, (2) assigned in a consistent and managed way, and (3)
assigned according to a common definition.
The assignment of URNs is done by an organization (or, in some cases,
according to an algorithm or other automated process) that has been
formally delegated a namespace within the "urn" scheme (e.g., a URN
in the 'example' namespace [RFC6963] might be of the form
"urn:example:foo").
This document rests on two key assumptions:
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1. Assignment of a URN is a managed process.
2. The space of URN namespaces is itself managed.
While other URI schemes may allow identifiers to be freely chosen and
assigned, such is not the case for URNs. The syntactical correctness
of a string starting with "urn:" is not sufficient to make it a URN.
In order for the string to be a valid URN, the namespace identifier
must be registered in accordance with the rules defined here and the
remaining parts of the full assigned-name portion of the URN must be
generated in accordance with the rules for the registered namespace.
So that information about both URN syntax and URN namespaces is
available in one place, this document does the following:
1. Defines the canonical syntax for URNs in general (in a way that
is consistent with URI syntax), specifies methods for determining
URN equivalence, and discusses URI conformance.
2. Specifies a method for defining a URN namespace and associating
it with a namespace identifier, and describes procedures for
registering namespace identifiers with the Internet Assigned
Numbers Authority (IANA).
For URN syntax and URN namespaces, this document modernizes and
replaces the definitions from [RFC2141] and [RFC3406]. These
modifications build on the requirements provided in [RFC1737] and
many years of experience with URNs, in both cases attempting to make
the smallest reasonable set of changes from the previous definitions.
The intent is to define URNs in a consistent manner so that, wherever
practical, the parsing, handling, and resolution of URNs can be
independent of the namespace within which a given URN is assigned.
This document obsoletes both [RFC2141] and [RFC3406].
2. Terminology
Several important terms used in this document, including some
"normalization" operations that are not part of the Unicode Standard
[UNICODE], are defined in the URI specification [RFC3986].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
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3. URN Syntax
The syntax of URNs as provided in [RFC2141] was defined before the
updated specification of URIs in [RFC3986]. In order to ensure
consistency with the URI syntax as well as semantic flexibility in
the use of URNs within particular applications (see
[I-D.ietf-urnbis-semantics-clarif] for further discussion), this
specification does the following:
o Extends URN syntax to explicitly allow the characters '/', "?",
and "#", which were reserved for future use by [RFC2141]; this
change effectively also allows several components of the URI
syntax although without tying those components to URI semantics.
o Defines syntax for an additional component that can be used in
interactions with a URN resolution service.
o Makes several smaller syntax adjustments.
However, this specification does not extend the URN syntax to allow
characters outside the ASCII range [RFC20], which implies that any
such characters need to be percent-encoded as described in
Section 2.1 of the URI specification [RFC3986].
The syntax for a URN is defined as follows using the Augmented
Backus-Naur Form (ABNF) as specified in [RFC5234]. Rules not defined
here (i.e., alphanum, pchar, path-absolute, query, and fragment) are
defined as part of the URI syntax [RFC3986] and used here to point
out the syntactic relationship with the terms used there.
namestring = assigned-name
[ "?" q-string ]
[ "??" r-string ]
[ "#" f-string ]
assigned-name = "urn" ":" NID ":" NSS
NID = (alphanum) 0*30(ldh) (alphanum)
ldh = alphanum / "-"
NSS = pchar *(pchar / "/")
q-string = pchar *( pchar / "/" / "?" )
r-string = pchar *( pchar / "/" / "?" )
f-string = fragment
Note: The character "?" can be used without percent-encoding inside
q-components, r-components, and f-components.
The following sections provide additional information about the
syntactic elements of URNs.
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3.1. Namespace Identifier
The syntax here is slightly more restrictive than what was defined in
[RFC2141]. This specification prohibits the character "-" at the end
of a NID.
NIDs are case insensitive (e.g., "ISBN" and "isbn" are equivalent).
Characters outside the ASCII range [RFC20] are not permitted in NIDs,
and no encoding mechanism for such characters is supported.
3.2. Namespace Specific String
The namespace specific string (NSS) is a unique identifier that is
assigned and managed in a consistent way and that conforms to the
definition of the relevant namespace. The combination of the NID
(unique across the entire "urn" scheme) and the NSS (unique within
the namespace) ensures that the resulting URN is a globally unique
URI.
This document modifies the syntax of the NSS to allow the following
characters: "/", "~", and "&".
In particular, allowing the "/" character effectively makes it
possible to encapsulate hierarchical identifiers from other naming
systems. For instance, consider the hypothetical example of a
hierarchical naming system in which the identifiers take the form of
a series of numbers separated by the "/" character, such as "1/406/
47452/2". If the naming authority for such identifiers were to use
URNs, it would be natural to place the existing identifiers in the
NSS, resulting in URNs such as "urn:example:1/406/47452/2".
Depending on the rules governing a namespace, names that are valid in
a namespace might contain characters that are not allowed by the
"pchar" production referenced above (e.g., characters outside the
ASCII range or characters that are reserved in URIs, such as "?", and
"#"). While such a string might be a valid name, it is not a valid
URN until it has been translated into a conformant NSS. Translation
is done by percent-encoding each disallowed character using the
method defined in Section 2.1 of the generic URI specification
[RFC3986]. Note that the "%" character is allowed in the NSS only
for the purpose of percent-encoding.
In order to make URNs as stable and persistent as possible when
protocols evolve and the environment around them changes, namespaces
SHOULD NOT allow characters outside the basic Latin repertoire
[RFC20] unless the nature of the particular namespace makes such
characters necessary.
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If a namespace designates one or more characters conforming to the
"pchar" rule as having special meaning for that namespace (e.g., "@")
and the namespace also uses that character in a literal sense, when
used in a literal sense the character MUST be percent-encoded (e.g.,
"%40"). For related considerations with regard to NID registration,
see Section 7.3.2.
3.3. Optional Components
The q-component, r-component, and f-component are optional components
that follow the assigned-name portion of the URN.
Because this specification focuses almost exclusively on URN syntax,
it does not define the semantics of the q-component, r-component, and
f-component for URNs in general. Instead, additional specifications
might establish these matters for URN-related services (such as URN
resolution) or for individual URN namespaces (e.g., to handle
extended information about the resource identified by a URN).
Defining the details of such usage is the responsibility of
specifications for URN resolution services, namespace registration
requests or specifications for individual namespaces, and other
appropriate documentation (such as policy documents governing the
management of a given URN namespace).
Unless specifically defined for a particular namespace after
publication of this document, use of these components is disallowed,
thereby maintaining strict backward compatibility with namespaces
defined in accordance with [RFC2141] and registered in accordance
with [RFC3406].
3.3.1. q-component
Although the URN q-component has close to the same syntax as the URI
query component, the URN q-component need not be semantically
equivalent to the URI query component and therefore is called by a
different name in this specification to emphasize that the
relationship is about syntax only (see also
[I-D.ietf-urnbis-semantics-clarif]).
The q-component is indicated by the first question mark ("?")
character and terminated by a double question mark ("??"), by a
number sign ("#") character, or by the end of the URI. The q-string
MUST NOT begin with a question mark ("?") since a double question
mark is reserved for use by an r-component (Section 3.3.2). The
characters slash ("/") and question mark ("?") may represent data
within the q-string. Note that characters outside the ASCII range
[RFC20] MUST be percent-encoded using the method defined in
Section 2.1 of the generic URI specification [RFC3986].
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As described under Section 4, the q-component SHALL NOT be taken into
account when determining URN equivalence.
The q-component is primarily intended to be used for passing
information in requests to the resources identified by a URN or to
applications that manage such resources. Consider the hypothetical
example of passing parameters to an application that returns metadata
about a resource (say, Dublin Core [RFC5013] data about a published
book). This could perhaps be accomplished by specifying the desired
metadata field (e.g., "description") in the q-component, resulting in
URNs such as
"urn:example:0-395-36341-1?operation=search&field=description".
However, this primary purpose is not intended to forestall other
potential uses for q-components.
3.3.2. r-component
The URN r-component has no syntactic equivalent in URIs.
The r-component is indicated by a double question mark ("??") and
terminated by a number sign ("#") character or by the end of the URI.
The characters slash ("/") and question mark ("?") may represent data
within the r-string. Note that characters outside the ASCII range
[RFC20] MUST be percent-encoded using the method defined in
Section 2.1 of the generic URI specification [RFC3986].
As described under Section 4, the r-component SHALL NOT be taken into
account when determining URN equivalence.
The r-component is primarily intended to be used for passing
information in requests to URN resolution services (not, as with the
q-component, to the resources identified by a URN or to applications
that manage such resources). Consider the hypothetical example of
passing parameters to resolution service (say, an ISO alpha-2 country
code [ISO3166-1] in order to scope down the preferred country in
which to search for a physical copy of a book). This could perhaps
be accomplished by specifying the country code in the r-component,
resulting in URNs such as "urn:example:0-395-36341-1??cc=uk".
However, this primary purpose is not intended to forestall other
potential uses for r-components.
This document defines only the syntax of the r-component and reserves
it for future use. The exact semantics of the r-component and its
use in URN resolution protocols are a matter for potential
standardization in separate specifications.
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3.3.3. f-component
Although the URN f-component has the same syntax as the URI fragment
component, the URN f-component need not be semantically equivalent to
the URI fragment component and therefore is called by a different
name in this specification to emphasize that the relationship is
about syntax only (see also [I-D.ietf-urnbis-semantics-clarif]).
The f-component is indicated by the presence of a number sign ("#")
character and terminated by the end of the URI. Note that characters
outside the ASCII range [RFC20] MUST be percent-encoded using the
method defined in Section 2.1 of the generic URI specification
[RFC3986].
As described under Section 4, the f-component SHALL NOT be taken into
account when determining URN equivalence.
The f-component is primarily intended to distinguish the integral
parts of resources named by URNs in particular namespaces. Consider
the hypothetical example of obtaining resources that are part of a
larger entity (say, the chapters of a book). Each part could be
specified in the f-component, resulting in URNs such as
"urn:example:978-952-10-7060-0#chapter1". However, this primary
purpose is not intended to forestall other potential uses for
f-components.
4. Equivalence of URNs
4.1. Procedure
For various purposes such as caching, often it is desirable to
determine if two URNs are "the same". This is done by testing for
equivalence (see Section 6.1 of [RFC3986]).
The generic URI specification [RFC3986] is very flexible about
equality comparisons, putting the focus on allowing false negatives
and avoiding false positives. If comparisons are made in a scheme-
independent way, i.e., as URI comparisons only, URNs that this
specification considers equal would be rejected. The discussion
below applies when the URIs involved are known to be URNs.
Two URNs are equivalent if their <assigned-name> portions are octet-
by-octet equal after applying case normalization (as specified in
Section 6.2.2.1 of [RFC3986]) to the following constructs:
1. the URI scheme "urn", by conversion to lower case
2. the NID, by conversion to lower case
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3. any percent-encoded characters in the NSS (that is, all character
triplets that match the <pct-encoding> production found in
Section 2.1 of the base URI specification [RFC3986]), by
conversion to upper case for the digits A-F.
Percent-encoded characters MUST NOT be decoded, i.e., percent-
encoding normalization (as specified in Section 6.2.2.2 of [RFC3986])
MUST NOT be applied.
If a q-component, r-component, or f-component (or any combination
thereof) are included in a URN, they MUST be ignored for purposes of
determining equivalence.
URN namespace definitions MAY include additional rules for
equivalence, such as case-insensitivity of the NSS (or parts
thereof). Such rules MUST always have the effect of eliminating some
of the false negatives obtained by the procedure above and MUST NOT
result in treating two URNs as not equivalent if the procedure here
says they are equivalent. For related considerations with regard to
NID registration, see below.
4.2. Examples
This section shows a variety of URNs (using the "example" NID defined
in [RFC6963]) that highlight the equivalence rules.
First, because the scheme and NID are case-insensitive, the following
URNs are equivalent to each other:
o urn:example:a123,z456
o URN:example:a123,z456
o urn:EXAMPLE:a123,z456
Second, because the q-component and f-component are not taken into
account for purposes of testing equivalence, the following URNs are
equivalent to the first three examples above:
o urn:example:a123,z456?abc
o urn:example:a123,z456#789
o urn:example:a123,z456#abc
Third, because the "/" character (and anything that follows it) in
the NSS is taken into account for purposes of equivalence, the
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following URNs are not equivalent to each other or to the preceding
URNs:
o urn:example:a123,z456/foo
o urn:example:a123,z456/bar
o urn:example:a123,z456/baz
Fourth, because of percent-encoding, the following URNs are
equivalent only to each other (although %2C is the percent-encoded
transformation of "," from the previous examples, such sequences are
not decoded for purposes of testing equivalence):
o urn:example:a123%2Cz456
o URN:EXAMPLE:a123%2cz456
Fifth, because characters other than percent-encoded sequences in the
NSS are treated in a case-sensitive manner (unless otherwise
specified for the namespace in question), the following URNs are not
equivalent to the first three URNs:
o urn:example:A123,z456
o urn:example:a123,Z456
Sixth, on casual visual inspection of a URN presented in a human-
oriented interface the following URN might appear the same as the
first three URNs (since U+0430 CYRILLIC SMALL LETTER A can be
confused with U+0061 LATIN SMALL LETTER A), but it is not equivalent:
o urn:example:%D0%B0123,z456
5. URI Conformance
5.1. Use in URI Protocol Slots
Because a URN is, syntactically, a URI under the "urn" scheme, in
theory a URN can be placed in any protocol slot that allows for a URI
(e.g., the 'href' and 'src' attributes in HTML, the <base/> element
in HTML, the 'xml:base' attribute in XML [XML-BASE], and the 'xmlns'
attribute in XML for XML namespace names [XML-NAMES]).
However, this does not imply that, semantically, it always makes
sense in practice to place a URN in a given URI protocol slot; in
particular, because a URN might not specify the location of a
resource or even point indirectly to one, it might not be appropriate
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to place a URN in a URI protocol slot that points to a resource
(e.g., the aforementioned 'href' and 'src' attributes).
Ultimately, guidelines regarding when it is appropriate to use URIs
under the "urn" scheme (or any other scheme) are the responsibility
of specifications for individual URI protocol slots (e.g., the
specification for the 'xml:base' attribute in XML might recommend
that it is inappropriate to use URNs in that protocol slot). This
specification cannot possibly anticipate all of the relevant cases,
and it is not the place of this specification to require or restrict
usage for individual protocol slots.
5.2. Parsing
In part because of the separation of semantics from syntax
[I-D.ietf-urnbis-semantics-clarif], generic URI processors need to
pay special attention to the parsing and analysis rules of RFC 3986
and, in particular, must treat the URI as opaque unless the scheme
and its requirements are recognized, in which case they may be in a
position to invoke scheme-appropriate processing such as by a URN
resolver. The URN resolver can either be an external resolver that
the URI resolver knows of, or it can be functionality built into the
URI resolver. Note that this requirement might impose constraints on
the contexts in which URNs are appropriately used; see Section 5.1.
5.3. URNs and Relative References
[RFC3986] Section 5.2 describes an algorithm for converting a URI
reference that might be relative to a given base URI into "parsed
components" of the target of that reference, which can then be
recomposed per RFC 3986 Section 5.3 into a target URI. This
algorithm cannot be applied directly to URNs because their syntax
does not support the necessary path components. The notion of a URN
as a "persistent", "permanent" identifier does not reconcile easily
with relative referencing. However, resources named with URNs may
contain relative references that do not apply to the URN itself.
Therefore a relative reference SHOULD NOT be evaluated directly with
respect to a URN. Instead, a relative reference SHOULD be evaluated
indirectly with respect to one of the following:
1. a base URI (other than a URN) declared by the resource itself; or
2. a base URI (other than a URN) obtained through the URN resolution
process; or
3. the URL of the resource as obtained through the URN resolution
process
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(Case 2 permits the resolution process to explicitly supply a base
URI if the resource content is supplied directly by the resolution
service rather than via an intermediate "location" URI.)
If no such base URI exists, use of a relative reference with respect
to a URN is an error and will yield results that might be unexpected
or not useful.
Resolution services SHOULD ensure that a base URI is supplied any
time they provide resource content directly to a client.
5.4. Transport and Display
When URNs are transported and exchanged, they MUST be represented in
the format defined herein. Further, all URN-aware applications MUST
offer the option of displaying URNs in this canonical form to allow
for direct transcription (for example by cut and paste techniques).
Such applications might support display of URNs in a more human-
friendly form and might use a character set that includes characters
that are not permitted in URN syntax as defined in this specification
(e.g., when displaying URNs to humans, such applications might
replace percent-encoded strings with characters from an extended
character repertoire such as Unicode [UNICODE]).
To minimize user confusion, a URI browser SHOULD display the complete
URN (including the "urn" scheme and any components) to ensure that
there is no confusion between URN namespace identifiers and URI
scheme identifiers. For example, a URI beginning with "urn:xmpp:"
[RFC4854] is very different from a URI beginning with "xmpp:"
[RFC5122]. Similarly, a potential DOI URI scheme [DOI-URI] is
different from, and possibly completely unrelated to, a possible DOI
URN namespace.
5.5. URI Design and Ownership
As mentioned, the assignment of URNs is a managed process, as is the
assignment of namespaces themselves. Although design of the URNs to
be assigned within a given namespace is ceded by this specification
to the namespace owner, doing so in a managed way avoids the problems
inherent in unmanaged generation of URIs as described in the
recommendations regarding URI design and ownership [RFC7320].
6. URN Namespaces
A URN namespace is a collection of identifiers that obey three
constraints: each identifier is (1) unique, (2) assigned in a
consistent way, and (3) assigned according to a common definition.
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1. The "uniqueness" constraint means that an identifier within the
namespace is never assigned to more than one resource and never
reassigned to a different resource, even if the identifier itself
is deprecated or becomes obsolete.
2. The "consistent assignment" constraint means that an identifier
within the namespace is assigned by an organization or created in
accordance with a process or algorithm that is always followed.
3. The "common definition" constraint means that there are clear
definitions for the syntax of identifiers within the namespace
and for the process of assigning or creating them.
A URN namespace is identified by a particular NID in order to ensure
the global uniqueness of URNs and, optionally, to provide a cue
regarding the structure of URNs assigned within a namespace.
With regard to global uniqueness, using different NIDs for different
collections of identifiers ensures that no two URNs will be the same
for different resources, since each collection is required to
uniquely assign each identifier. However, a single resource can have
more than one URN assigned to it for different purposes (for example,
if a book were published in a monograph series, it could have both an
ISBN [RFC3187] and an ISSN [RFC3044] assigned to it, resulting in two
URNs referring to the same book). Subject to other constraints, such
as those imposed by the URI syntax [RFC3986], the rules of the URN
scheme are intended to allow preserving the normal and natural form
of identifiers specified elsewhere when they are treated as URN
namespaces.
With regard to the structure of URNs assigned within a namespace, the
development of an identifier structure (and thereby a collection of
identifiers) depends on the requirements of the community defining
the identifiers, how the identifiers will be assigned and used, etc.
These issues are beyond the scope of URN syntax and the general rules
for URN namespaces, because they are specific to the community
defining a namespace (e.g., the bibliographic and publishing
communities in the case of the 'ISBN' and 'ISSN' namespaces, or the
developers of extensions to the Extensible Messaging and Presence
Protocol in the case of the 'XMPP' namespace).
URN namespaces inherit certain rights and responsibilities by the
nature of URNs, e.g.:
1. They uphold the general principles of a well-managed URN
namespace by providing persistent identification of resources and
unique assignment of identifier strings in accordance with a
common definition.
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2. Optionally, they can be registered in global registration
services.
There are two types of URN namespace: formal and informal. These are
distinguished by the expected level of service, the information
needed to define the namespace, and the procedures for registration.
Because the majority of the namespaces registered so far have been
formal, this document concentrates on formal namespaces.
Note: [RFC3406] defined a third type of "experimental namespaces",
denoted by prefixing the namespace identifier with the string "X-".
Consistent with general IETF conclusions about similar approaches
[RFC6648], this specification removes the experimental category and
syntax. Because experimental namespaces were never registered,
removing the experimental category has no impact on the existing
registries or future registration procedures. Because they are not
registered, strings that refer to existing experimental namespaces
are not valid URNs. Truly experimental usages can, of course, employ
the 'example' namespace [RFC6963].
6.1. Formal Namespaces
A formal namespace provides benefit to some subset of users on the
Internet. In particular, it would not make sense for a formal
namespace to be used only by a community or network that is not
connected to the Internet. For example, it would be inappropriate
for a NID to effectively force someone to use a proprietary network
or service not open to the general Internet user. The intent is
that, while the community of those who might actively use the names
assigned within that NID might be small, the potential use of
identifiers within that NID is open to any user on the Internet.
Formal NIDs might be appropriate even when some aspects are not fully
open. For example, a namespace might make use of a fee-based,
privately managed, or proprietary registry for assignment of URNs in
the namespace. However, it might still benefit some Internet users
if the associated services have openly-published identifiers.
An organization that will assign URNs within a formal namespace
SHOULD meet the following criteria:
1. Organizational stability and the ability to maintain the URN
namespace for a long time; absent such evidence, it ought to be
clear how the namespace can remain viable if the organization can
no longer maintain the namespace.
2. Competency in name assignment. This will improve the likelihood
of persistence (e.g. to minimize the likelihood of conflicts).
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3. Commitment to not reassigning existing names and to allowing old
names to continue to be valid (e.g., if the assignee of a name is
no longer a member or customer of the assigning organization, if
various information about the assignee or named entity happens to
change, or even if the assignee or the named entity itself is no
longer in existence; in all these cases, the name is still
valid).
A formal namespace establishes a particular NID, subject to the
following constraints (above and beyond the syntax rules already
specified):
1. It MUST NOT be an already-registered NID.
2. It MUST NOT start with "urn-" (which is reserved for informal
namespaces).
3. It MUST be more than two characters long.
4. It MUST NOT start with "aa-", where "aa" is any combination of
two ASCII letters and the hyphen is followed by something other
than another hyphen.
5. It MUST NOT start with the string "xn--" or any other string
consisting of two letters followed by two hyphens. Those strings
are reserved for potential representation of DNS A-labels and
similar strings in the future [RFC5890].
All two-letter strings, and all two-letter strings followed by "-"
and any sequence of valid NID characters, are reserved for potential
use as NIDs based on ISO alpha-2 country codes [ISO3166-1] for
eventual national registrations of URN namespaces. The definition
and scoping of rules for allocation of responsibility for such
country-code-based namespaces is beyond the scope of this document.
Applicants and reviewers considering new NIDs should also be aware
that they may be considered as names with semantic implications and
hence a source of conflict. Particular attention should be paid to
strings that might be construed as names of, or registered under the
authority of, countries (including ISO 3166-1 alpha-3 codes) and to
strings that might imply association with well-known trademarks. In
line with traditional policies, disputes about "ownership" of
particular strings are disagreements among the parties involved;
neither IANA nor the IETF will become involved in such disputes
except in response to orders from a court of competent jurisdiction.
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6.2. Informal Namespaces
Informal namespaces are full-fledged URN namespaces, with all the
associated rights and responsibilities. Informal namespaces differ
from formal namespaces in the process for assigning a NID: for an
informal namespace, the registrant does not designate the NID;
instead, IANA assigns a NID consisting of the string 'urn-' followed
by one or more digits (e.g., "urn-7") where the digits consist of the
next available number in the sequence of positive integers assigned
to informal namespaces. Thus the syntax of an informal namespace is:
InformalNamespaceName = "urn-" Number
Number = DigitNonZero 0*Digit
DigitNonZero = "1"/ "2" / "3" / "4"/ "5"
/ "6" / "7" / "8" / "9"
Digit = "0" / DigitNonZero
The only restrictions on <Number> are that it (1) consist strictly of
ASCII digits, that it (2) not have leading zeros, and that it (3) not
cause the NID to exceed the length limitations defined for the URN
syntax.
7. Defining and Registering a URN Namespace
7.1. Overview
Because the space of URN namespaces is itself managed, the definition
of a namespace SHOULD pay particular attention to:
1. The purpose of the namespace.
2. The syntax of URNs assigned within the namespace, including
whether q-components, r-components, or f-components are allowed.
3. The process for assigning URNs within the namespace.
4. The security implications of assigning URNs within the namespace
and using the assigned URNs.
5. Any potential interoperability issues with URNs assigned within
the namespace.
6. Optionally, the process for resolving URNs issued within the
namespace.
The section on completing the template (Section 7.3) explains these
matters in greater detail.
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7.2. Registration Policy and Process
The basic registration policy for URN namespaces is Expert Review as
defined in the "IANA Considerations" document [RFC5226]. For
namespaces or their definitions that are intended to become standards
or normative components of standards, the output of the Expert Review
process is intended to be a report, rather than instructions to IANA
to take action (see below). The key steps are:
1. Fill out the namespace registration template (see Section 7.3 and
Appendix A). This can be done as part of an Internet-Draft or a
specification in another series, although that is not necessary.
2. Send the completed template to the urn@ietf.org discussion list
for review.
3. If necessary to address comments received, repeat steps 1 and 2.
4. If the designated experts approve the request and no
standardization action is involved, the IANA will register the
requested NID. If standardization is anticipated, the designated
experts will prepare a report and forward it to the appropriate
standards approval body (the IESG in the case of the IETF) and
IANA will register the requested NID only after receiving
directions from that body and a copy of the expert review report.
A namespace registration can be revised by updating the registration
template, following the same steps outlined above for new
registrations. A revised registration MUST describe differences from
prior versions and SHOULD make special note of any relevant changes
in the underlying technologies or namespace management processes.
Experience to date with namespace registration requests has shown
that registrants sometimes do not initially understand some of the
subtleties of URN namespaces, and that defining the namespace in the
form of a specification enables the registrants to clearly formulate
their "contract" with the intended user community. Therefore,
although the registration policy for formal namespaces is Expert
Review and a specification is not strictly required, it is
RECOMMENDED for registrants to provide a stable specification
documenting the namespace definition and expanding upon the issues
described herein.
Because naming can be difficult and contentious, namespace
registrants and the designated experts are strongly encouraged to
work together in a spirit of good faith and mutual understanding to
achieve rough consensus (see [RFC7282]) on handling registration
requests. They are also encouraged to bring additional expertise
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into the discussion if that would be helpful in providing perspective
or otherwise resolving issues.
Especially when iterations in the registration process are prolonged,
designated experts are expected to take reasonable precautions to
avoid race conditions on proposed NID names and, if such situations
arise, to encourage applicants to work out any conflicts among
themselves.
7.3. Completing the Template
A template for defining and registering a URN namespace is provided
in Appendix A. This section describes considerations for completing
the template.
7.3.1. Purpose
The "Purpose" section of the template describes matters such as:
1. The kinds of resources identified by URNs assigned within the
namespace.
2. Why it is preferable to use URNs rather than some other
technology (e.g., separate URI schemes or URIs in existing
schemes) and why no existing URN namespace is a good fit.
3. The kinds of software applications that can use or resolve the
assigned URNs (e.g., by differentiating among disparate
namespaces, identifying resources in a persistent fashion, or
meaningfully resolving and accessing services associated with the
namespace).
4. The scope of the namespace (public vs. private, global vs. local
to a particular organization, nation, or industry). For example,
a namespace claiming to deal in "national identification numbers"
might be expected to have a global scope and address all identity
number structures, whereas a URN scheme for a particular national
identification number system would need to handle only the
structure for that nation's identity numbers.
5. How the intended community (and the Internet community at large)
will benefit from using or resolving the assigned URNs.
6. If the namespace or its definition are expected to become an
integral and/or normative element of a standard being developed
in the IETF or some other recognized standards body, that
intention should be noted in this section.
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7.3.2. Syntax
The "Syntax" section of the template contains:
1. A description of the structure of URNs within the namespace, in
conformance with the fundamental URN syntax. The structure might
be described in terms of a formal definition (e.g., using
Augmented BNF for Syntax Specifications (ABNF) as specified in
[RFC5234]), an algorithm for generating conformant URNs, or a
regular expression for parsing the identifier into components;
alternatively, the structure might be opaque.
2. Any special character encoding rules for assigned URNs (e.g.,
which character ought to always be used for quotes).
3. Rules for determining equivalence between two identifiers in the
namespace. Such rules ought to always have the effect of
eliminating false negatives that might otherwise result from
comparison. If it is appropriate and helpful, reference can be
made to specific equivalence rules defined in the URI
specification [RFC3986]. Examples of equivalence rules include
equivalence between uppercase and lowercase characters in the
Namespace Specific String, between hyphenated and non-hyphenated
groupings in the identifier string, or between single-quotes and
double-quotes. (Note that these are not normative statements for
any kind of best practice related to handling of equivalences
between characters in general; they are statements limited to one
particular namespace only.)
4. Any special considerations necessary for conforming with the URN
syntax. This is particularly applicable in the case of existing
naming systems that are used in the context of URNs. For
example, if a namespace is used in contexts other than URNs, it
might make use of characters that are reserved in the URN syntax.
This section ought to note any such characters, and outline
necessary mappings to conform to URN syntax. Normally, this will
be handled by percent-encoding the character as specified in
Section 2.1 of the URI specification [RFC3986].
7.3.3. Assignment
The "Assignment" section of the template describes matters such as:
1. Mechanisms or authorities for assigning URNs to resources. It
ought to make clear whether assignment is completely open (e.g.,
following a particular procedure such as first-come, first-served
(FCFS)), completely closed (e.g., for a private organization), or
limited in various ways (e.g., delegated to authorities
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recognized by a particular organization); if limited, it ought to
explain how to become an assigner of identifiers or how to
request assignment of identifiers from existing assignment
authorities.
2. Methods for ensuring that URNs within the namespace are unique.
For example, identifiers might be assigned sequentially or in
accordance with some well-defined process by a single authority,
assignment might be partitioned among delegated authorities that
are individually responsible for respecting uniqueness rules, or
URNs might be created independently following an algorithm that
itself guarantees uniqueness.
7.3.4. Security and Privacy
The "Security and Privacy" section of the template describes any
potential issues related to security and privacy with regard to
assignment, use, and resolution of identifiers within the namespace.
Examples of such issues include:
o The consequences of producing false negatives and false positives
during comparison for equivalence (see "Issues in Identifier
Comparison for Security Purposes" [RFC6943])
o Leakage of private information when identifiers are communicated
on the public Internet
o The potential for directory harvesting
o Various issues discussed in the guidelines for security
considerations in RFCs [RFC3552] and the privacy considerations
for Internet protocols [RFC6973].
7.3.5. Interoperability
The "Interoperability" section MUST specify any potential issues
related to interoperability. Examples include possible confusion
with other URN namespaces or naming systems because of syntax (e.g.,
percent-encoding of certain characters) or scope (e.g., overlapping
areas of interest). If at all possible, concerns that arise during
the registration of a URN namespace (e.g., due to the syntax or scope
of an identifier system) SHOULD be resolved as part of the
registration process.
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7.3.6. Resolution
The "Resolution" section MUST specify whether resolution mechanisms
are intended or anticipated for URNs assigned within the namespace
(e.g., URNs within some namespaces are intended to act as abstract
designators and thus are not intended to be resolved).
If resolution is intended, then this section SHOULD specify whether
the organization that assigns URNs within the namespace intends to
operate or recommend any resolution services for URNs within that
namespace. In addition, if the assigning organization intends to
implement registration for publicly advertised resolution services
(for example using a system based on principles similar to those
described in [RFC2276] and [RFC2483]), then this section SHOULD list
or reference the requirements for being publicly advertised by the
assigning organization.
8. IANA Considerations
8.1. URI Scheme
This section updates the registration of the 'urn' URI scheme in the
Permanent URI Registry [URI-Registry] .
[Note to RFC Editor: please replace "[ this document ]" with "RFC"
and the number assigned to this document upon publication.]
URI Scheme Name: urn
Status: permanent
URI Scheme Syntax: See Section 3 of [ this document ].
URI Scheme Semantics: The 'urn' scheme identifies Uniform Resource
Names, which are persistent, location-independent resource
identifiers.
Encoding Considerations: See Section 3 of [ this document ].
Applications/Protocols That Use This URI Scheme Name: Uniform
Resource Names are used in a wide variety of applications,
including bibliographic reference systems and as names for
Extensible Markup Language (XML) namespaces.
Interoperability Considerations: See Section 5 of [ this document ].
Security Considerations: See Section 7.3.4 and Section 9 of [ this
document ].
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Contact: URNBIS WG [mailto:urn@ietf.org]
Author/Change Controller: This scheme is registered under the IETF
tree. As such, the IETF maintains change control.
References None.
8.2. Registration of URN Namespaces
This document outlines the processes for registering URN namespaces,
and has implications for the IANA in terms of registries to be
maintained (see especially Section 7). In all cases, the IANA ought
to assign the appropriate NID (formal or informal) once the
procedures outlined in this document have been completed.
9. Security and Privacy Considerations
The definition of a URN namespace needs to account for potential
security and privacy issues related to assignment, use, and
resolution of identifiers within the namespace (e.g., some namespace
resolvers might assign special meaning to certain characters in the
Namespace Specific String); see Section 7.3.4 for further discussion.
In most cases, URN namespaces provide a way to declare public
information. Nominally, these declarations will have a relatively
low security profile, however there is always the danger of
"spoofing" and providing misinformation. Information in these
declarations ought to be taken as advisory.
10. References
10.1. Normative References
[RFC20] Cerf, V., "ASCII format for network interchange", RFC 20,
October 1969.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 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.
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[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
10.2. Informative References
[DOI-URI] Paskin, N., Neylon, E., Hammond, T., and S. Sun, "The
"doi" URI Scheme for the Digital Object Identifier (DOI)",
June 2003,
<http://tools.ietf.org/id/draft-paskin-doi-uri-04.txt>.
[I-D.ietf-urnbis-semantics-clarif]
Klensin, J., "URN Semantics Clarification", draft-ietf-
urnbis-semantics-clarif-01 (work in progress), February
2015.
[ISO3166-1]
ISO, "Codes for the representation of names of countries
and their subdivisions -- Part 1: Country codes", ISO
3166-1:2013, 2013.
[RFC1737] Sollins, K. and L. Masinter, "Functional Requirements for
Uniform Resource Names", RFC 1737, December 1994.
[RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.
[RFC2276] Sollins, K., "Architectural Principles of Uniform Resource
Name Resolution", RFC 2276, January 1998.
[RFC2483] Mealling, M. and R. Daniel, "URI Resolution Services
Necessary for URN Resolution", RFC 2483, January 1999.
[RFC3044] Rozenfeld, S., "Using The ISSN (International Serial
Standard Number) as URN (Uniform Resource Names) within an
ISSN-URN Namespace", RFC 3044, January 2001.
[RFC3187] Hakala, J. and H. Walravens, "Using International Standard
Book Numbers as Uniform Resource Names", RFC 3187, October
2001.
[RFC3406] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
"Uniform Resource Names (URN) Namespace Definition
Mechanisms", BCP 66, RFC 3406, October 2002.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
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[RFC4854] Saint-Andre, P., "A Uniform Resource Name (URN) Namespace
for Extensions to the Extensible Messaging and Presence
Protocol (XMPP)", RFC 4854, April 2007.
[RFC5013] Kunze, J. and T. Baker, "The Dublin Core Metadata Element
Set", RFC 5013, August 2007.
[RFC5122] Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)", RFC
5122, February 2008.
[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010.
[RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham,
"Deprecating the "X-" Prefix and Similar Constructs in
Application Protocols", BCP 178, RFC 6648, June 2012.
[RFC6943] Thaler, D., "Issues in Identifier Comparison for Security
Purposes", RFC 6943, May 2013.
[RFC6963] Saint-Andre, P., "A Uniform Resource Name (URN) Namespace
for Examples", BCP 183, RFC 6963, May 2013.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973, July
2013.
[RFC7282] Resnick, P., "On Consensus and Humming in the IETF", RFC
7282, June 2014.
[RFC7320] Nottingham, M., "URI Design and Ownership", BCP 190, RFC
7320, July 2014.
[UNICODE] The Unicode Consortium, "The Unicode Standard", 2015-,
<http://www.unicode.org/versions/latest/>.
[URI-Registry]
IANA, "Permanent URI Schemes", <http://www.iana.org/
assignments/uri-schemes/uri-schemes.xhtml#uri-schemes-1>.
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[XML-BASE]
Marsh, J. and R. Tobin, "XML Base (Second Edition)", World
Wide Web Consortium Recommendation REC-xmlbase-20090128,
January 2009,
<http://www.w3.org/TR/2009/REC-xmlbase-20090128>.
[XML-NAMES]
Thompson, H., Hollander, D., Layman, A., Bray, T., and R.
Tobin, "Namespaces in XML 1.0 (Third Edition)", World Wide
Web Consortium Recommendation REC-xml-names-20091208,
December 2009,
<http://www.w3.org/TR/2009/REC-xml-names-20091208>.
Appendix A. Registration Template
A.1. Namespace ID
Requested of IANA (formal) or assigned by IANA (informal).
A.2. Version
The version of the registration, starting with 1 and incrementing by
1 with each new version.
A.3. Date
The date when the registration is requested of IANA, using the format
YYYY-MM-DD.
A.4. Registrant
The person or organization that has registered the NID, including the
following information:
o The name and address of the registering organization.
o The name and contact information (email, phone number, and/or
postal address) of the designated contact person.
A.5. Purpose
Described under Section 7.3.1 of this document.
A.6. Syntax
Described under Section 7.3.2 of this document. Unless the
registration explicitly says otherwise, use of p-, q-, and/or
f-components is not allowed for this namespace.
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A.7. Assignment
Described under Section 7.3.3 of this document.
A.8. Security and Privacy
Described under Section 7.3.4 of this document.
A.9. Interoperability
Described under Section 7.3.5 of this document.
A.10. Resolution
Described under Section 7.3.6 of this document.
A.11. Documentation
A pointer to an RFC, a specification published by another standards
development organization, or another stable document that provides
further information about the namespace.
A.12. Revision Information
(Applicable only when earlier registrations have been revised.)
Description of changes from prior version(s).
Appendix B. Changes from RFC 2141
This document makes the following substantive changes from [RFC2141]:
o Formally registers 'urn' as a URI scheme.
o Disallows "-" at the end of a NID.
o Allows the "/", "~", and "&" characters in the namespace-specific
string (NSS).
o Allows q-components, r-components, and f-components.
Appendix C. Changes from RFC 3406
This document makes the following substantive changes from [RFC3406]:
1. Relaxes the registration policy for formal namespaces from "IETF
Review" to "Expert Review" as discussed in Section 7.2.
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2. Removes the category of experimental namespaces, consistent with
[RFC6648].
3. Simplifies the registration template.
In addition, some of the text has been updated to be consistent with
the definition of Uniform Resource Identifiers (URIs) [RFC3986] and
the processes for registering information with the IANA [RFC5226], as
well as more modern guidance with regard to security [RFC3552] and
privacy [RFC6973] issues and identifier comparison [RFC6943].
Appendix D. Contributors
RFC 2141, which provided the basis for the syntax portion of this
document, was authored by Ryan Moats.
RFC 3406, which provided the basis for the namespace portion of this
document, was authored by Leslie Daigle, Dirk-Willem van Gulik,
Renato Iannella, and Patrik Faltstrom.
Their work is gratefully acknowledged.
Appendix E. Acknowledgements
Many thanks to Marc Blanchet, Leslie Daigle, Martin Duerst, Juha
Hakala, Ted Hardie, Alfred Hoenes, Paul Jones, Barry Leiba, Sean
Leonard, Larry Masinter, Keith Moore, Mark Nottingham, Julian
Reschke, Lars Svensson, Henry S. Thompson, Dale Worley, and other
participants in the URNBIS WG for their input. Alfred Hoenes in
particular edited an earlier version of this document and served as
co-chair of the URNBIS WG.
Juha Hakala deserves special recognition for his dedication to
successfully completing this work, as do Andrew Newton and Melinda
Shore in their roles as working group co-chairs and Barry Leiba in
his role as area director.
Appendix F. Change log for versions of draft-ietf-urnbis-rfc2141bis-urn
[[RFC Editor: please remove this appendix before publication.]]
F.1. Changes from -08 to -09
o Altered the text in Section 5 to reflect list discussions about
the earlier phrasing. Also added DOI example and citation to that
section.
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o Clarified the naming rules for formal namespaces and their
relationship to ISO 3166, IDNA, etc., reserved strings.
o Added an explicit statement about use of URNs in various protocols
and contexts to Section 5.
o Clarified that experimental namespace NIDs, which were explicitly
not registered, are not valid URNs (in Section 6.
o Transformed the partial production in Section 6.2 into valid ABNF.
o Added more text about p-/q-/f-components and recommendations about
use.
o Added clarifying note about "?" within q-components and
f-components.
o Added explicit requirement that revisions of existing
registrations document the changes and added a slot for that
description to the template.
o Many small editorial changes and adjustments including adding
additional references and cross-references for clarification.
o Inserted a placeholder for additional examples.
F.2. Changes from -09 to -10
o Several clarifying editorial changes, most suggested by Ted Hardie
and Henry S. Thompson (some of them off-list).
o Added a large number of placeholders that identify issues that
require WG consideration and resolution (or WG delegation to the
editors).
F.3. Changes from -10 to -11
o Removed most of the placeholders added in -10. Supplied new text
as required or suggested by on-list discussion of those issues.
o Replaced the conformance examples Section 4.2 with a more complete
collection and discussion.
o Revised and consolidated the registration procedure, and added
provisions for NIDs that are the subject of standards and for
avoiding race conditions about NID strings.
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o In response to independent comments from Ted Hardie and Henry S.
Thompson, called attention to the possibility of conflicts between
NID strings and various claims of national, corporate, and other
perogatives.
o Changed the production for assigned-name as suggested by Lars
Svensson.
o Several clarifying editorial changes including correcting a glitch
in instructions to the RFC Editor.
F.4. Changes from -11 to -12
o Removed p-components as a standalone construct, and instead folded
them into the NSS.
o Defined syntax for r-components as a way to pass information to
resolvers, but left the semantics for future standardization
efforts.
o Further tuned the discussion of interoperability and related
registration issues.
o Made a number of editorial corrections and reorganized the syntax
material in Section 3 somewhat to make it internally consistent
and keep the relationship to RFC 3986 clear.
Authors' Addresses
Peter Saint-Andre
&yet
Email: peter@andyet.com
URI: https://andyet.com/
John C Klensin
1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140
USA
Phone: +1 617 245 1457
Email: john-ietf@jck.com
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