Network Working Group                                     D. Thaler, Ed.
Internet-Draft                                                 Microsoft
Obsoletes: 4395 (if approved)                                  T. Hansen
Intended status: Best Current Practice                 AT&T Laboratories
Expires: August 18, 2014                                       T. Hardie
                                                             L. Masinter
                                                       February 14, 2014

       Guidelines and Registration Procedures for New URI Schemes


   This document updates the guidelines and recommendations, as well as
   the IANA registration processes, for the definition of Uniform
   Resource Identifier (URI) schemes.  It obsoletes RFC 4395.

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
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   Drafts is at

   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 August 18, 2014.

Copyright Notice

   Copyright (c) 2014 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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must

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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Guidelines for Permanent Scheme Definitions . . . . . . . . .   4
     3.1.  Demonstratable, New, Long-Lived Utility . . . . . . . . .   4
     3.2.  Syntactic Compatibility . . . . . . . . . . . . . . . . .   5
     3.3.  Well-Defined  . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Definition of Operations  . . . . . . . . . . . . . . . .   6
     3.5.  Context of Use  . . . . . . . . . . . . . . . . . . . . .   6
     3.6.  Internationalization and Character Encoding . . . . . . .   7
     3.7.  Clear Security Considerations . . . . . . . . . . . . . .   7
     3.8.  Scheme Name Considerations  . . . . . . . . . . . . . . .   7
   4.  Guidelines for Provisional URI Scheme Registration  . . . . .   8
   5.  Guidelines for Historical URI Scheme Registration . . . . . .   9
   6.  Guidelines for Private URI Scheme Use . . . . . . . . . . . .   9
   7.  URI Scheme Registration Procedure . . . . . . . . . . . . . .   9
     7.1.  General . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.2.  Registration Procedures . . . . . . . . . . . . . . . . .  10
     7.3.  Change Control  . . . . . . . . . . . . . . . . . . . . .  12
     7.4.  URI Scheme Registration Template  . . . . . . . . . . . .  12
   8.  The "example" Scheme  . . . . . . . . . . . . . . . . . . . .  14
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  15
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     12.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  Changes Since RFC 4395 . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   The Uniform Resource Identifier (URI) protocol element and generic
   syntax is defined by [RFC3986].  Each URI begins with a scheme name,
   as defined by Section 3.1 of RFC 3986, that refers to a specification
   for identifiers within that scheme.  The URI syntax provides a
   federated and extensible naming system, where each scheme's
   specification may further restrict the syntax and define the
   semantics of identifiers using that scheme.

   This document obsoletes [RFC4395], which in turn obsoleted [RFC2717]
   and [RFC2718].  Recent documents have used the term "URI" for all
   resource identifiers, avoiding the term "URL" and reserving the term

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   "URN" explicitly for those URIs using the "urn" scheme name
   ([RFC2141]).  URN "namespaces" ([RFC3406]) are specific to the "urn"
   scheme and are not covered explicitly by this specification.

   This document provides updated guidelines for the definition of new
   schemes, for consideration by those who are defining, registering, or
   evaluating those definitions, as well as a process and mechanism for
   registering schemes within the IANA URI Schemes registry.  There is a
   single namespace for registered schemes.  The intent of the registry
   is to:

   o  provide a central point of discovery for established URI scheme
      names, and easy location of their defining documents;

   o  discourage use of the same scheme name for different purposes;

   o  help those proposing new scheme names to discern established
      trends and conventions, and avoid names that might be confused
      with existing ones;

   o  encourage registration by setting a low barrier for registration.

   As originally defined, URIs only allowed a limited repertoire of
   characters chosen from US-ASCII.  An Interationalized Resource
   Identifier (IRI), as defined by [RFC3987], extends the URI syntax to
   allow characters from a much greater repertoire, to accomodate
   resource identifiers from the world's languages.  RFC 3987 [RFC3987]
   also defined a mapping between URIs and IRIs.  A URI scheme name is
   the same as the corresponding IRI scheme name.  Thus, there is no
   separate, independent registry or registration process for IRI
   schemes: the URI Schemes registry is used for both URIs and IRIs.
   Those who wish to describe resource identifiers that are useful as
   IRIs should define the corresponding URI syntax, and note that the
   IRI usage follows the rules and transformations defined in [RFC3987].

   [RFC3986] defines the overall syntax for URIs as:

             URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

   A scheme definition cannot override the overall syntax for URIs.  For
   example, this means that fragment identifiers (#) cannot be re-used
   outside the generic syntax restrictions.  A scheme definition must
   specify the scheme name and the syntax of the scheme-specific part,
   which is clarified as follows:

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               URI = scheme ":" scheme-specific-part [ "#" fragment ]

               scheme-specific-part = hier-part [ "?" query ]

2.  Terminology

   Within this document, the key words MUST, MAY, SHOULD, REQUIRED,
   RECOMMENDED, and so forth are used within the general meanings
   established in [RFC2119], within the context that they are
   requirements on future registrations.

   This document distinguishes between a "scheme specification", being a
   document defining the syntax and semantics of a scheme, vs. a "scheme
   registration request" being the request submitted to IANA.  The term
   "scheme definition" refers generically to the syntax and semantics of
   a scheme, typically documented in a scheme specification.

3.  Guidelines for Permanent Scheme Definitions

   This section gives considerations for new schemes.  Meeting these
   guidelines is REQUIRED for permanent scheme registration.  Permanent
   status is appropriate for, but not limited to, use in standards.  For
   IETF Standards-Track documents, Permanent registration status is

3.1.  Demonstratable, New, Long-Lived Utility

   In general, the use and deployment of new schemes in the Internet
   infrastructure may be costly; some parts of URI processing may be
   scheme-dependent.  Introducing a new scheme may require additional
   software, not only for client software and user agents but also in
   additional parts of the network infrastructure (gateways, proxies,
   caches) [W3CWebArch].  Since scheme names share a single, global
   namespace, it is desirable to avoid contention over use of short,
   mnemonic scheme names.  New schemes should have utility to the
   Internet community beyond that available with already registered
   schemes.  The scheme specification SHOULD discuss the utility of the
   scheme being registered.  [[CREF1: Previously, "scheme definition"
   above was "registration document", which was ambiguous as to whether
   the scheme specification or the IANA registration request was meant.
   But the template in this document has no field for this, so updated
   as currently written.  --DT]]

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3.2.  Syntactic Compatibility

   [RFC3986] defines the generic syntax for all URI schemes, along with
   the syntax of common URI components that are used by many URI schemes
   to define hierarchical identifiers.  [RFC3987] extended this generic
   syntax to cover IRIs.  All scheme specifications MUST define their
   own URI <scheme-specific-part> syntax.  Care must be taken to ensure
   that all strings matching their scheme-specific syntax will also
   match the <absolute-URI> grammar described in [RFC3986].

   New schemes SHOULD reuse the common URI components of [RFC3986] for
   the definition of hierarchical naming schemes.  If there is a strong
   reason for a scheme not to use the hierarchical syntax, then the new
   scheme definition SHOULD follow the syntax of previously registered

   Schemes that are not intended for use with relative URIs SHOULD avoid
   use of the forward slash "/" character, which is used for
   hierarchical delimiters, and the complete path segments "." and ".."

   Schemes should avoid improper use of "//".  The use of double slashes
   in the first part of a URI is not an artistic indicator that what
   follows is a URI: Double slashes are intended for use ONLY when the
   syntax of the <scheme-specific-part> contains a hierarchical
   structure.  In URIs from such schemes, the use of double slashes
   indicates that what follows is the top hierarchical element for a
   naming authority.  (Section 3.2 of RFC 3986 has more details.)
   Schemes that do not contain a conformant hierarchical structure in
   their <scheme-specific-part> SHOULD NOT use double slashes following
   the "<scheme>:" string.

   New schemes SHOULD clearly define the role of [RFC3986] reserved
   characters in URIs of the scheme being defined.  The syntax of the
   new scheme should be clear about which of the "reserved" set of
   characters are used as delimiters within the URIs of the new scheme,
   and when those characters must be escaped, versus when they may be
   used without escaping.

3.3.  Well-Defined

   While URIs may or may not be defined as locators in practice, a
   scheme definition itself MUST be clear as to how it is expected to
   function.  Schemes that are not intended to be used as locators
   SHOULD describe how the resource identified can be determined or
   accessed by software that obtains a URI of that scheme.

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   For schemes that function as locators, it is important that the
   mechanism of resource location be clearly defined.  This might mean
   different things depending on the nature of the scheme.

   In many cases, new schemes are defined as ways to translate between
   other namespaces or protocols and the general framework of URIs.  For
   example, the "ftp" scheme translates into the FTP protocol, while the
   "mid" scheme translates into a Message-ID identifier of an email
   message.  For such schemes, the description of the mapping MUST be
   complete, and in sufficient detail so that the mapping in both
   directions is clear: how to map from a URI into an identifier or set
   of protocol actions or name in the target namespace, and how legal
   values in the base namespace, or legal protocol interactions, might
   be represented in a valid URI.  In particular, the mapping SHOULD
   describe the mechanisms for encoding binary or character strings
   within valid character sequences in a URI (see Section 3.6 for
   guidelines).  If not all legal values or protocol interactions of the
   base standard can be represented using the scheme, the definition
   SHOULD be clear about which subset are allowed, and why.

3.4.  Definition of Operations

   As part of the definition of how a URI identifies a resource, a
   scheme definition SHOULD define the applicable set of operations that
   may be performed on a resource using the URI as its identifier.  A
   model for this is HTTP; an HTTP resource can be operated on by GET,
   POST, PUT, and a number of other operations available through the
   HTTP protocol.  The scheme definition SHOULD describe all well-
   defined operations on the resource identifier, and what they are
   supposed to do.

   Some schemes don't fit into the "information access" paradigm of
   URIs.  For example, "telnet" provides location information for
   initiating a bi-directional data stream to a remote host; the only
   operation defined is to initiate the connection.  In any case, the
   operations appropriate for a scheme SHOULD be documented.

   Note: It is perfectly valid to say that "no operation apart from GET
   is defined for this URI".  It is also valid to say that "there's only
   one operation defined for this URI, and it's not very GET-like".  The
   important point is that what is defined on this scheme is described.

3.5.  Context of Use

   In general, URIs are used within a broad range of protocols and
   applications.  Most commonly, URIs are used as references to
   resources within directories or hypertext documents, as hyperlinks to
   other resources.  In some cases, a scheme is intended for use within

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   a different, specific set of protocols or applications.  If so, the
   scheme definition SHOULD describe the intended use and include
   references to documentation that define the applications and/or
   protocols cited.

3.6.  Internationalization and Character Encoding

   When describing schemes in which (some of) the elements of the URI
   are actually representations of human-readable text, care should be
   taken not to introduce unnecessary variety in the ways in which
   characters are encoded into octets and then into URI characters; see
   [RFC3987] and Section 2.5 of [RFC3986] for guidelines.  If URIs of a
   scheme contain any text fields, the scheme definition MUST describe
   the ways in which characters are encoded and any compatibility issues
   with IRIs of the scheme.

   The scheme specification SHOULD be as restrictive as possible
   regarding what characters are allowed in the URI, because some
   characters can create several different security considerations (see,
   for example [RFC4690]).

   All percent-encoded variants are automatically included by definition
   for any character given in an IRI production.  This means that if you
   want to restrict the URI percent-encoded forms in some way, you must
   restrict the Unicode forms that would lead to them.

3.7.  Clear Security Considerations

   Definitions of schemes MUST be accompanied by a clear analysis of the
   security implications for systems that use the scheme; this follows
   the practice of Security Consideration sections within IANA
   registrations [RFC5226].

   In particular, Section 7 of RFC 3986 [RFC3986] describes general
   security considerations for URIs, while [RFC3987] gives those for
   IRIs.  The definition of an individual scheme should note which of
   these apply to the specified scheme.

3.8.  Scheme Name Considerations

   Section 3.1 of RFC 3986 defines the syntax of a URI scheme name; this
   syntax remains the same for IRIs.  New registered schemes
   registrations MUST follow this syntax, which only allows a limited
   repertoire of characters (taken from US-ASCII).  Although the syntax
   for the scheme name in URIs is case insensitive, the scheme names
   itself MUST be registered using lowercase letters.

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   Scheme names should be short, but also sufficiently descriptive and
   distinguished to avoid problems.

   Avoid names or other symbols that might cause problems with rights to
   use the name in IETF specifications and Internet protocols.  For
   example, be careful with trademark and service mark names.  (See
   Section 7.4 of [RFC3978].)

   Avoid using names that are either very general purpose or associated
   in the community with some other application or protocol.  Avoid
   scheme names that are overly general or grandiose in scope (e.g.,
   that allude to their "universal" or "standard" nature.)

   Organizations that desire their own namespace for URI scheme names
   are encouraged to use a prefix based on their domain name, expressed
   in reverse order.  For example, a URI scheme name of
   might be used by the organization that owns the domain
   name.  [[CREF2: Open Issue: Should we define a mechanism to register
   a scheme prefix ("web+", "ms-", etc.)?  --DT]] [[CREF3: Open Issue:
   Are strings that look like reversed FQDNs (other than grandfathered
   ones like "iris.beep") reserved for use as such?  Proposed answer is
   Yes, new schemes should not use a "." unless they are actually
   constructed from a domain name.  --DT]]

4.  Guidelines for Provisional URI Scheme Registration

   Provisional registration can be used for schemes that are not part of
   any standard, but that are intended for use (or observed to be in
   use) outside a private environment within a single organization.
   Provisional registration can also be used as an intermediate step on
   the way to permanent registration, e.g., before the scheme
   specification is finalized as a standard.

   [[CREF4: Open issue: previously this also RECOMMENDED following the
   same guidelines as for permanent registration.  However, this higher
   bar disincented people to register schemes at all, and hence
   interfered with the goals of the registry.  Hence tentatively
   removed, but need to confirm consensus on this.  --DT]] For a
   provisional registration, the following are REQUIRED:

   o  The scheme name meets the syntactic requirements of Section 3.8
      and the encoding requirements of Section 3.6.

   o  There MUST NOT already be an entry with the same scheme name.  (In
      the unfortunate case that there are multiple, different uses of
      the same scheme name, the IESG may approve a request to modify an
      existing entry to note the separate use.)  [[CREF5: Open Issue:
      Must the IESG do this?  Why not the Expert Reviewer?  --??]]

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   o  Contact information identifying the person supplying the
      registration is included.  Previously unregistered schemes
      discovered in use may be registered by third parties (even if not
      on behalf of those who created the scheme).  In this case, both
      the registering party and the scheme creator SHOULD be identified.

   o  If no permanent, citable specification for the scheme definition
      is included, credible reasons for not providing it SHOULD be

   o  The scheme definition SHOULD include a clear Security
      Considerations (Section 3.7) or explain why a full security
      analysis is not available (e.g., in a third-party scheme

   o  If the scheme definition does not meet the guidelines laid out in
      Section 3, the differences and reasons SHOULD be noted.

5.  Guidelines for Historical URI Scheme Registration

   In some circumstances, it is appropriate to note a scheme that was
   once in use or registered but for whatever reason is no longer in
   common use or the use is not recommended.  In this case, it is
   possible for an individual to request that the URI scheme be
   registered (newly, or as an update to an existing registration) as
   'historical'.  Any scheme that is no longer in common use MAY be
   designated as historical; the registration should contain some
   indication to where the scheme was previously defined or documented.

6.  Guidelines for Private URI Scheme Use

   Unregistered schemes can cause problems if used outside a private
   environment within a single organization.  For example, the use could
   leak out beyond the closed environment, or other colliding uses of
   the same scheme name could occur within the closed environment.  As
   such, a unique namespace (see Section 3.8) should be used, and it is
   strongly encouraged to do a Provisional registration even in such
   cases.  [[CREF6: TODO: This is closely related to the open issue of
   prefix registrations.  --DT]]

7.  URI Scheme Registration Procedure

7.1.  General

   [[CREF7: We are updating this, but have not made changes.  --??]]
   [[CREF8: Open Issue: Should Provisional status just use First Come
   First Serve?  Someone suggested FCFS with Expert Review afterwards,
   but the benefit and efficacy of a subsequent Expert Review seems

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   dubious to me and might only serve to deter registrations in the
   first place, which is the problem we're trying to solve.  --DT]] The
   scheme registration process is described in the terminology of
   [RFC5226].  The registration process is an optional mailing list
   review, followed by "Expert Review".  The registration request should
   note the desired status.  The Designated Expert will evaluate the
   request against the criteria of the requested status.  In the case of
   a permanent registration request, the Designated Expert may:

   o  Accept the specification of the scheme for permanent registration.

   o  Suggest provisional registration instead.

   o  Request IETF review and IESG approval; in the meanwhile, suggest
      provisional registration.

   Scheme definitions contained within other IETF documents
   (Informational, Experimental, or Standards-Track RFCs) must also
   undergo Expert Review; in the case of Standards-Track documents,
   permanent registration status approval is REQUIRED.

   The registration procedure is intended to be very lightweight for
   non-contentious registrations.  For the most part, we expect the good
   sense of submitters and reviewers, guided by these procedures, to
   achieve an acceptable and useful consensus for the community.

   In exceptional cases, where the negotiating parties cannot form a
   consensus, the final arbiter of any contested registration shall be
   the IESG.

   [[CREF9: TODO: We don't want this.  --??]] If parties achieve
   consensus on a registration proposal that does not fully conform to
   the strict wording of this procedure, this should be drawn to the
   attention of a relevant member of the IESG.

7.2.  Registration Procedures

   Someone wishing to register a new scheme MUST:

   1.  Check the IANA URI Schemes registry to see whether there is
       already an entry for the desired name.  If there is already an
       entry under the name, choose a different scheme name, or update
       the existing scheme definition.

   2.  Prepare a scheme registration request using the template
       specified in Section 7.4.  The scheme registration request may be
       contained in an Internet Draft, submitted alone, or as part of
       some other permanently available, stable, protocol specification.

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       The completed template may also be submitted in some other form
       (as part of another document or as a stand-alone document), but
       the contents will be treated as an "IETF Contribution" under the
       guidelines of [RFC3978].  [[CREF10: Open Issue: I think the last
       phrase above about RFC 3978 is problematic, as it just serves to
       discourage registration.  For example, third-party registrations
       may have no way to grant such rights or make such assertions.
       Similarly, a standard published by another SDO may have policy/
       process issues having a request treated as an IETF contribution.
       Recommend deleting this sentence.  --DT]]

   3.  If the registration request is for a Permanent registration:

       1.  Send a copy of the completed template or a pointer to the
           containing document (with specific reference to the section
           with the completed template) to the mailing list uri-
  , requesting review.  In addition, request
           review on other relevant mailing lists as appropriate.  For
           example, general discussion of URI syntactical issues could
           be discussed on; schemes for a network protocol
           could be discussed on a mailing list for that protocol.
           Allow a reasonable time for discussion and comments.  Four
           weeks is reasonable for a permanent registration requests.

       2.  Respond to review comments and make revisions to the proposed
           registration as needed to bring it into line with the
           guidelines given in this document.

   4.  Submit the (possibly updated) registration template (or pointer
       to document containing it) to IANA at

   Upon receipt of a scheme registration request, the following steps
   MUST be followed:

   1.  IANA checks the submission for completeness; if sections are
       missing or citations are not correct, IANA may reject the
       registration request.

   2.  IANA checks the current registry for a entry with the same name;
       if such an entry exists, IANA may reject the registration

   3.  IANA enters the registration request in the IANA registry, with
       status marked as "Pending Review".

   4.  IANA requests Expert Review of the registration request against
       the corresponding guidelines from this document.

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   5.  The Designated Expert may request additional review or
       discussion, as necessary.

   6.  If Expert Review recommends 'provisional' or 'permanent'
       registration, IANA adds the registration to the registry with
       appropriate review.

   7.  Unless Expert Review has explicitly rejected the registration
       request within two weeks, IANA should automatically add the
       registration to the registry as 'provisional'.

   Either based on an explicit request or independently initiated, the
   Designated Expert or IESG may request the upgrade of a 'provisional'
   registration to a 'permanent' one.  In such cases, IANA should update
   the status of the corresponding entry.  [[CREF11: Open Issue: Say
   more about guidance to the Designated Expert.  Under what
   circumstance should this happen?  --DT]]

7.3.  Change Control

   Registrations may be updated in the registry by the same mechanism as
   required for an initial registration.  In cases where the original
   definition of the scheme is contained in an IESG-approved document,
   update of the specification also requires IESG approval.

   Provisional registrations may be updated by the original registrant
   or anyone designated by the original registrant.  In addition, the
   IESG may reassign responsibility for a provisional registration
   scheme, or may request specific changes to a scheme registration.
   This will enable changes to be made to schemes where the original
   registrant is out of contact, or unwilling or unable to make changes.

   Transition from 'provisional' to 'permanent' status may be requested
   and approved in the same manner as a new 'permanent' registration.
   Transition from 'permanent' to 'historical' status requires IESG
   approval.  Transition from 'provisional' to 'historical' may be
   requested by anyone authorized to update the provisional

7.4.  URI Scheme Registration Template

   This template describes the fields that must be supplied in a scheme
   registration request:

   Scheme name:
     See Section 3.8 for guidelines.


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     This reflects the status requested, and should be one of
     'permanent', 'provisional', or 'historical'.

   Scheme syntax:
     See Section 3.2 for guidelines.

   Scheme semantics:
     See Section 3.3 and Section 3.4 for guidelines.

   Encoding considerations:
     See Section 3.3 and Section 3.6 for guidelines.

   Applications/protocols that use this scheme name:
     See Section 3.5.

   Interoperability considerations:
     If the person or group registering the scheme is aware of any
     details regarding the scheme that might impact interoperability,
     identify them here.  For example: proprietary or uncommon encoding
     methods; inability to support multibyte character sets;
     incompatibility with types or versions of any underlying protocol.

   Security considerations:
     See Section 3.7 for guidelines.

     Person (including contact information) to contact for further

   Author/Change controller:
     Person (including contact information) authorized to change this.

     Include full citations for all referenced documents.  Registration
     templates for provisional registration may be included in an
     Internet Draft; when the documents expire or are approved for
     publication as an RFC, the registration will be updated.

   [[CREF12: Open Issue: Some of the fields above may serve to deter
   registration.  Should some of them NOT be required for Provisional
   registrations (including third-party ones)?  For example, the
   requirement to have clear security considerations is not appropriate
   for third-party registrations.  Typically one is forced to fill in
   something like "Unknown, use with care."  These seem to me to be more
   appropriate inside the specification (if any) in the references,
   rather than being required in the request template.  Thus, as new
   specifications update the uses (e.g., allow use with another HTTP

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   method), the IANA registry itself shouldn't be required to be
   updated.  --DT]]

8.  The "example" Scheme

   There is a need for a scheme name that can be used for examples in
   documentation without fear of conflicts with current or future actual
   schemes.  The scheme "example" is hereby registered as a Permanent
   scheme for that purpose.

   Scheme name:  example

   Status:  permanent

   Scheme syntax:  The entire range of allowable syntax specified in
     [RFC3986] is allowed for "example" URIs.

   Scheme semantics:  URIs in the "example" scheme should be used for
     documentation purposes only.  The use of "example" URIs must not be
     used as locators, identify any resources, or specify any particular
     set of operations.

   Encoding considerations:  See Section 2.5 of [RFC3986] for

   Applications/protocols that use this scheme name:  An "example" URI
     should be used for documentation purposes only.  It MUST NOT be
     used for any protocol.

   Interoperability considerations:  None.

   Security considerations:  None.

   Contact:  N/A

   Author/Change controller:  IETF

   References:  This RFC XXXX.
     RFC Editor Note: Replace XXXX with this RFC's reference.

9.  IANA Considerations

   Previously, the former "URL Scheme" registry was replaced by the
   "Uniform Resource Identifier (URI) Schemes" registry.  The process
   was based on [RFC5226] "Expert Review" with an initial (optional)
   mailing list review.

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   The updated template has an additional field for the status of the
   scheme, and the procedures for entering new name schemes have been
   augmented.  Section 7 establishes the process for new scheme

   IANA is requested to do the following:

   o  Update the URI Schemes registry to point to this document.

   o  Combine the "Permanent URI Schemes", "Provisional URI Schemes",
      and "Historical URI Schemes" sub-registries into a single common
      registry with an additional "Status" column containing the status
      (Permanent, Provisional, Historical, or Pending Review).

   o  Add the "example" URI scheme to the registry (see the template
      above for registration).

10.  Security Considerations

   All registered values are expected to contain accurate security
   consideration sections; 'permanent' registered scheme names are
   expected to contain complete definitions.

   Information concerning possible security vulnerabilities of a
   protocol may change over time.  Consequently, claims as to the
   security properties of a registered scheme may change as well.  As
   new vulnerabilities are discovered, information about such
   vulnerabilities may need to be attached to existing documentation, so
   that users are not misled as to the true security properties of a
   registered scheme.

11.  Acknowledgements

   Many thanks to Patrik Faltstrom, Paul Hoffmann, Ira McDonald, Roy
   Fielding, Stu Weibel, Tony Hammond, Charles Lindsey, Mark Baker, and
   other members of the mailing list for their comments on
   earlier versions.

   Parts of this document are based on [RFC2717], [RFC2718] and
   [RFC3864].  Some of the ideas about use of URIs were taken from the
   "Architecture of the World Wide Web" [W3CWebArch].

12.  References

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12.1.  Normative References

   [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.

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

   [RFC3978]  Bradner, S., "IETF Rights in Contributions", RFC 3978,
              March 2005.

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

12.2.  Informative References

   [RFC2717]  Petke, R. and I. King, "Registration Procedures for URL
              Scheme Names", BCP 35, RFC 2717, November 1999.

   [RFC2718]  Masinter, L., Alvestrand, H., Zigmond, D., and R. Petke,
              "Guidelines for new URL Schemes", RFC 2718, November 1999.

   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", BCP 66, RFC 3406, October 2002.

   [RFC3864]  Klyne, G., Nottingham, M., and J. Mogul, "Registration
              Procedures for Message Header Fields", BCP 90, RFC 3864,
              September 2004.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [RFC4395]  Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
              Registration Procedures for New URI Schemes", BCP 35, RFC
              4395, February 2006.

   [RFC4690]  Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
              Recommendations for Internationalized Domain Names
              (IDNs)", RFC 4690, September 2006.

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              W3C Technical Architecture Group, "Architecture of the
              World Wide Web, Volume One", December 2004,

Appendix A.  Changes Since RFC 4395

   1.  Combined the Historical, Permanent, and Provisional URI Schemes
       registries into one registry with a status column.  This is done
       to make it easier to prevent duplicates and see existing

   2.  Clarified that a "URI scheme name" and an "IRI scheme name" are
       the same thing and thus use the same IANA registry.

   3.  Clarified that mailing list review is not required for
       Provisional registrations.

   4.  Added the "example:" URI scheme.

   5.  Added text about when to use Provisional registration.

   6.  Updated convention for Private scheme prefix to use "." instead
       of "-" between domain name labels, to reduce chance of collision.

Authors' Addresses

   Dave Thaler (editor)
   One Microsoft Way
   Redmond, WA  98052

   Phone: +1 425 703 8835

   Tony Hansen
   AT&T Laboratories
   200 Laurel Ave.
   Middletown, NJ  07748


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   Ted Hardie

   Phone: +1 408 628 5864

   Larry Masinter
   345 Park Ave.
   San Jose, CA  95110

   Phone: +1 408 536 3024

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