draft-ietf-iri-3987bis-12.txt   draft-ietf-iri-3987bis-13.txt 
Internationalized Resource Identifiers M. Duerst Internationalized Resource Identifiers M. Duerst
(iri) Aoyama Gakuin University (iri) Aoyama Gakuin University
Internet-Draft M. Suignard Internet-Draft M. Suignard
Obsoletes: 3987 (if approved) Unicode Consortium Obsoletes: 3987 (if approved) Unicode Consortium
Intended status: Standards Track L. Masinter Intended status: Standards Track L. Masinter
Expires: January 17, 2013 Adobe Expires: April 23, 2013 Adobe
July 16, 2012 October 20, 2012
Internationalized Resource Identifiers (IRIs) Internationalized Resource Identifiers (IRIs)
draft-ietf-iri-3987bis-12 draft-ietf-iri-3987bis-13
Abstract Abstract
This document defines the Internationalized Resource Identifier (IRI) This document defines the Internationalized Resource Identifier (IRI)
protocol element, as an extension of the Uniform Resource Identifier protocol element, as an extension of the Uniform Resource Identifier
(URI). An IRI is a sequence of characters from the Universal (URI). An IRI is a sequence of characters from the Universal
Character Set (Unicode/ISO 10646). Grammar and processing rules are Character Set (Unicode/ISO 10646). Grammar and processing rules are
given for IRIs and related syntactic forms. given for IRIs and related syntactic forms.
Defining IRI as a new protocol element (rather than updating or Defining IRI as a new protocol element (rather than updating or
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public-iri@w3.org, archives at public-iri@w3.org, archives at
http://lists.w3.org/archives/public/public-iri/. For a list of open http://lists.w3.org/archives/public/public-iri/. For a list of open
issues, please see the issue tracker of the WG at issues, please see the issue tracker of the WG at
http://trac.tools.ietf.org/wg/iri/trac/report/1. For a list of http://trac.tools.ietf.org/wg/iri/trac/report/1. For a list of
individual edits, please see the change history at individual edits, please see the change history at
http://trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis. http://trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis.
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and PDF. It is also available in HTML from and PDF. It is also available in HTML from
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www.sw.it.aoyama.ac.jp/2012/pub/draft-ietf-iri-3987bis-12.utf8.txt. www.sw.it.aoyama.ac.jp/2012/pub/draft-ietf-iri-3987bis-13.utf8.txt.
While all these versions are identical in their technical content, While all these versions are identical in their technical content,
the HTML, PDF, and UTF-8 plaintext versions show non-Unicode the HTML, PDF, and UTF-8 plaintext versions show non-Unicode
characters directly. This often makes it easier to understand characters directly. This often makes it easier to understand
examples, and readers are therefore advised to consult these versions examples, and readers are therefore advised to consult these versions
in preference or as a supplement to the ASCII version. in preference or as a supplement to the ASCII version.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 17, 2013. This Internet-Draft will expire on April 23, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Overview and Motivation . . . . . . . . . . . . . . . . . 5 1.1. Overview and Motivation . . . . . . . . . . . . . . . . . 5
1.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 6 1.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 7 1.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 7
1.4. Notation . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4. Notation . . . . . . . . . . . . . . . . . . . . . . . . 8
2. IRI Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2. IRI Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1. Summary of IRI Syntax . . . . . . . . . . . . . . . . . . 9 2.1. Summary of IRI Syntax . . . . . . . . . . . . . . . . . . 9
2.2. ABNF for IRI References and IRIs . . . . . . . . . . . . 10 2.2. ABNF for IRI References and IRIs . . . . . . . . . . . . 10
3. Processing IRIs and related protocol elements . . . . . . . . 13 3. Processing IRIs and related protocol elements . . . . . . . . 12
3.1. Converting to UCS . . . . . . . . . . . . . . . . . . . . 13 3.1. Converting to UCS . . . . . . . . . . . . . . . . . . . . 13
3.2. Parse the IRI into IRI components . . . . . . . . . . . . 13 3.2. Parse the IRI into IRI components . . . . . . . . . . . . 13
3.3. General percent-encoding of IRI components . . . . . . . 14 3.3. General percent-encoding of IRI components . . . . . . . 13
3.4. Mapping ireg-name . . . . . . . . . . . . . . . . . . . . 14 3.4. Mapping ireg-name . . . . . . . . . . . . . . . . . . . . 14
3.4.1. Mapping using Percent-Encoding . . . . . . . . . . . . 14 3.4.1. Mapping using Percent-Encoding . . . . . . . . . . . . 14
3.4.2. Mapping using Punycode . . . . . . . . . . . . . . . . 15 3.4.2. Mapping using Punycode . . . . . . . . . . . . . . . . 14
3.4.3. Additional Considerations . . . . . . . . . . . . . . 15 3.4.3. Additional Considerations . . . . . . . . . . . . . . 15
3.5. Mapping query components . . . . . . . . . . . . . . . . 16 3.5. Mapping query components . . . . . . . . . . . . . . . . 16
3.6. Mapping IRIs to URIs . . . . . . . . . . . . . . . . . . 16 3.6. Mapping IRIs to URIs . . . . . . . . . . . . . . . . . . 16
4. Converting URIs to IRIs . . . . . . . . . . . . . . . . . . . 16 4. Converting URIs to IRIs . . . . . . . . . . . . . . . . . . . 16
4.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . 18 4.1. Limitations . . . . . . . . . . . . . . . . . . . . . . . 16
4.2. Conversion . . . . . . . . . . . . . . . . . . . . . . . 17
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 18
5. Use of IRIs . . . . . . . . . . . . . . . . . . . . . . . . . 19 5. Use of IRIs . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.1. Limitations on UCS Characters Allowed in IRIs . . . . . . 19 5.1. Limitations on UCS Characters Allowed in IRIs . . . . . . 19
5.2. Software Interfaces and Protocols . . . . . . . . . . . . 20 5.2. Software Interfaces and Protocols . . . . . . . . . . . . 20
5.3. Format of URIs and IRIs in Documents and Protocols . . . 21 5.3. Format of URIs and IRIs in Documents and Protocols . . . 20
5.4. Use of UTF-8 for Encoding Original Characters . . . . . . 21 5.4. Use of UTF-8 for Encoding Original Characters . . . . . . 21
5.5. Relative IRI References . . . . . . . . . . . . . . . . . 23 5.5. Relative IRI References . . . . . . . . . . . . . . . . . 22
6. Legacy Extended IRIs (LEIRIs) . . . . . . . . . . . . . . . . 23 6. Legacy Extended IRIs (LEIRIs) . . . . . . . . . . . . . . . . 23
6.1. Legacy Extended IRI Syntax . . . . . . . . . . . . . . . 23 6.1. Legacy Extended IRI Syntax . . . . . . . . . . . . . . . 23
6.2. Conversion of Legacy Extended IRIs to IRIs . . . . . . . 24 6.2. Conversion of Legacy Extended IRIs to IRIs . . . . . . . 23
6.3. Characters Allowed in Legacy Extended IRIs but not in 6.3. Characters Allowed in Legacy Extended IRIs but not in
IRIs . . . . . . . . . . . . . . . . . . . . . . . . . . 24 IRIs . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7. URI/IRI Processing Guidelines (Informative) . . . . . . . . . 26 7. Processing of URIs/IRIs/URLs by Web Browsers . . . . . . . . . 25
7.1. URI/IRI Software Interfaces . . . . . . . . . . . . . . . 26 8. URI/IRI Processing Guidelines (Informative) . . . . . . . . . 26
7.2. URI/IRI Entry . . . . . . . . . . . . . . . . . . . . . . 26 8.1. URI/IRI Software Interfaces . . . . . . . . . . . . . . . 26
7.3. URI/IRI Transfer between Applications . . . . . . . . . . 27 8.2. URI/IRI Entry . . . . . . . . . . . . . . . . . . . . . . 26
7.4. URI/IRI Generation . . . . . . . . . . . . . . . . . . . 27 8.3. URI/IRI Transfer between Applications . . . . . . . . . . 27
7.5. URI/IRI Selection . . . . . . . . . . . . . . . . . . . . 28 8.4. URI/IRI Generation . . . . . . . . . . . . . . . . . . . 27
7.6. Display of URIs/IRIs . . . . . . . . . . . . . . . . . . 29 8.5. URI/IRI Selection . . . . . . . . . . . . . . . . . . . . 28
7.7. Interpretation of URIs and IRIs . . . . . . . . . . . . . 29 8.6. Display of URIs/IRIs . . . . . . . . . . . . . . . . . . 29
7.8. Upgrading Strategy . . . . . . . . . . . . . . . . . . . 30 8.7. Interpretation of URIs and IRIs . . . . . . . . . . . . . 29
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 8.8. Upgrading Strategy . . . . . . . . . . . . . . . . . . . 30
9. Security Considerations . . . . . . . . . . . . . . . . . . . 31 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32 10. Security Considerations . . . . . . . . . . . . . . . . . . . 31
11. Main Changes Since RFC 3987 . . . . . . . . . . . . . . . . . 33 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 32
11.1. Split out Bidi, processing guidelines, comparison 12. Main Changes Since RFC 3987 . . . . . . . . . . . . . . . . . 32
sections . . . . . . . . . . . . . . . . . . . . . . . . 33 12.1. Split out Bidi, processing guidelines, comparison
11.2. Major restructuring of IRI processing model . . . . . . . 33 sections . . . . . . . . . . . . . . . . . . . . . . . . 32
11.2.1. OLD WAY . . . . . . . . . . . . . . . . . . . . . . . 33 12.2. Major restructuring of IRI processing model . . . . . . . 32
11.2.2. NEW WAY . . . . . . . . . . . . . . . . . . . . . . . 34 12.2.1. OLD WAY . . . . . . . . . . . . . . . . . . . . . . . 33
11.2.3. Extension of Syntax . . . . . . . . . . . . . . . . . 34 12.2.2. NEW WAY . . . . . . . . . . . . . . . . . . . . . . . 33
11.2.4. More to be added . . . . . . . . . . . . . . . . . . . 34 12.2.3. Extension of Syntax . . . . . . . . . . . . . . . . . 33
11.3. Change Log . . . . . . . . . . . . . . . . . . . . . . . 34 12.2.4. More to be added . . . . . . . . . . . . . . . . . . . 34
11.3.1. Changes after draft-ietf-iri-3987bis-01 . . . . . . . 34 12.3. Change Log . . . . . . . . . . . . . . . . . . . . . . . 34
11.3.2. Changes from draft-duerst-iri-bis-07 to 12.3.1. Changes after draft-ietf-iri-3987bis-01 . . . . . . . 34
12.3.2. Changes from draft-duerst-iri-bis-07 to
draft-ietf-iri-3987bis-00 . . . . . . . . . . . . . . 34 draft-ietf-iri-3987bis-00 . . . . . . . . . . . . . . 34
11.3.3. Changes from -06 to -07 of draft-duerst-iri-bis . . . 34 12.3.3. Changes from -06 to -07 of draft-duerst-iri-bis . . . 34
11.4. Changes from -00 to -01 . . . . . . . . . . . . . . . . . 35 12.4. Changes from -00 to -01 . . . . . . . . . . . . . . . . . 34
11.5. Changes from -05 to -06 of draft-duerst-iri-bis-00 . . . 35 12.5. Changes from -05 to -06 of draft-duerst-iri-bis-00 . . . 34
11.6. Changes from -04 to -05 of draft-duerst-iri-bis . . . . . 35 12.6. Changes from -04 to -05 of draft-duerst-iri-bis . . . . . 35
11.7. Changes from -03 to -04 of draft-duerst-iri-bis . . . . . 35 12.7. Changes from -03 to -04 of draft-duerst-iri-bis . . . . . 35
11.8. Changes from -02 to -03 of draft-duerst-iri-bis . . . . . 35 12.8. Changes from -02 to -03 of draft-duerst-iri-bis . . . . . 35
11.9. Changes from -01 to -02 of draft-duerst-iri-bis . . . . . 35 12.9. Changes from -01 to -02 of draft-duerst-iri-bis . . . . . 35
11.10. Changes from -00 to -01 of draft-duerst-iri-bis . . . . . 36 12.10. Changes from -00 to -01 of draft-duerst-iri-bis . . . . . 35
11.11. Changes from RFC 3987 to -00 of draft-duerst-iri-bis . . 36 12.11. Changes from RFC 3987 to -00 of draft-duerst-iri-bis . . 35
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
12.1. Normative References . . . . . . . . . . . . . . . . . . 36 13.1. Normative References . . . . . . . . . . . . . . . . . . 36
12.2. Informative References . . . . . . . . . . . . . . . . . 37 13.2. Informative References . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction 1. Introduction
1.1. Overview and Motivation 1.1. Overview and Motivation
A Uniform Resource Identifier (URI) is defined in [RFC3986] as a A Uniform Resource Identifier (URI) is defined in [RFC3986] as a
sequence of characters chosen from a limited subset of the repertoire sequence of characters chosen from a limited subset of the repertoire
of US-ASCII [ASCII] characters. of US-ASCII [ASCII] characters.
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character sequences that can result in the same presentation. character sequences that can result in the same presentation.
This document defines the protocol element called Internationalized This document defines the protocol element called Internationalized
Resource Identifier (IRI), which allows applications of URIs to be Resource Identifier (IRI), which allows applications of URIs to be
extended to use resource identifiers that have a much wider extended to use resource identifiers that have a much wider
repertoire of characters. It also provides corresponding repertoire of characters. It also provides corresponding
"internationalized" versions of other constructs from [RFC3986], such "internationalized" versions of other constructs from [RFC3986], such
as URI references. The syntax of IRIs is defined in Section 2. as URI references. The syntax of IRIs is defined in Section 2.
Within this document, Section 5 discusses the use of IRIs in Within this document, Section 5 discusses the use of IRIs in
different situations. Section 7 gives additional informative different situations. Section 8 gives additional informative
guidelines. Section 9 discusses IRI-specific security guidelines. Section 10 discusses IRI-specific security
considerations. considerations.
This specification is part of a collection of specifications intended This specification is part of a collection of specifications intended
to replace [RFC3987]. [Bidi] discusses the special case of to replace [RFC3987]. [Bidi] discusses the special case of
bidirectional IRIs, IRIs using characters from scripts written right- bidirectional IRIs, IRIs using characters from scripts written right-
to-left. [Equivalence] gives guidelines for applications wishing to to-left. [Equivalence] gives guidelines for applications wishing to
determine if two IRIs are equivalent, as well as defining some determine if two IRIs are equivalent, as well as defining some
equivalence methods. [RFC4395bis] updates the URI scheme equivalence methods. [RFC4395bis] updates the URI scheme
registration guidelines and procedures to note that every URI scheme registration guidelines and procedures to note that every URI scheme
is also automatically an IRI scheme and to allow scheme definitions is also automatically an IRI scheme and to allow scheme definitions
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[RFC4395bis]. For example, this is the practice for IMAP URLs [RFC4395bis]. For example, this is the practice for IMAP URLs
[RFC2192], POP URLs [RFC2384] and the URN syntax [RFC2141]). Note [RFC2192], POP URLs [RFC2384] and the URN syntax [RFC2141]). Note
that use of percent-encoding may also be restricted in some that use of percent-encoding may also be restricted in some
situations, for example, URI schemes that disallow percent- situations, for example, URI schemes that disallow percent-
encoding might still be used with a fragment identifier which is encoding might still be used with a fragment identifier which is
percent-encoded (e.g., [XPointer]). See Section 5.4 for further percent-encoded (e.g., [XPointer]). See Section 5.4 for further
discussion. discussion.
1.3. Definitions 1.3. Definitions
The following definitions are used in this document; they follow the Various terms used in this document are defined in [RFC6365] and
terms in [RFC2130], [RFC2277], and [ISO10646]. [RFC3986]. In addition, we define the following terms for use in
this document.
character: A member of a set of elements used for the organization,
control, or representation of data. For example, "LATIN CAPITAL
LETTER A" names a character.
octet: An ordered sequence of eight bits considered as a unit. octet: An ordered sequence of eight bits considered as a unit.
character repertoire: A set of characters (set in the mathematical
sense).
sequence of characters: A sequence of characters (one after sequence of characters: A sequence of characters (one after
another). another).
sequence of octets: A sequence of octets (one after another). sequence of octets: A sequence of octets (one after another).
character encoding: A method of representing a sequence of character encoding: A method of representing a sequence of
characters as a sequence of octets (maybe with variants). Also, a characters as a sequence of octets (maybe with variants). Also, a
method of (unambiguously) converting a sequence of octets into a method of (unambiguously) converting a sequence of octets into a
sequence of characters. sequence of characters.
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relative. However, the "IRI" that results from such a reference relative. However, the "IRI" that results from such a reference
only includes absolute IRIs; any relative IRI references are only includes absolute IRIs; any relative IRI references are
resolved to their absolute form. Note that in [RFC2396] URIs did resolved to their absolute form. Note that in [RFC2396] URIs did
not include fragment identifiers, but in [RFC3986] fragment not include fragment identifiers, but in [RFC3986] fragment
identifiers are part of URIs. identifiers are part of URIs.
LEIRI (Legacy Extended IRI): This term is used in various XML LEIRI (Legacy Extended IRI): This term is used in various XML
specifications to refer to strings that, although not valid IRIs, specifications to refer to strings that, although not valid IRIs,
are acceptable input to the processing rules in Section 6.2. are acceptable input to the processing rules in Section 6.2.
running text: Human text (paragraphs, sentences, phrases) with
syntax according to orthographic conventions of a natural
language, as opposed to syntax defined for ease of processing by
machines (e.g., markup, programming languages).
protocol element: Any portion of a message that affects processing protocol element: Any portion of a message that affects processing
of that message by the protocol in question. of that message by the protocol in question.
create (a URI or IRI): With respect to URIs and IRIs, the term is create (a URI or IRI): With respect to URIs and IRIs, the term is
used for the initial creation. This may be the initial creation used for the initial creation. This may be the initial creation
of a resource with a certain identifier, or the initial exposition of a resource with a certain identifier, or the initial exposition
of a resource under a particular identifier. of a resource under a particular identifier.
generate (a URI or IRI): With respect to URIs and IRIs, the term is generate (a URI or IRI): With respect to URIs and IRIs, the term is
used when the identifier is generated by derivation from other used when the identifier is generated by derivation from other
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[RFC3986], which does not mandate a particular registered name lookup [RFC3986], which does not mandate a particular registered name lookup
technology. For further background, see [RFC6055] and [Gettys]. technology. For further background, see [RFC6055] and [Gettys].
3.4.2. Mapping using Punycode 3.4.2. Mapping using Punycode
In situations where it is certain that <ireg-name> is intended to be In situations where it is certain that <ireg-name> is intended to be
used as a domain name to be processed by Domain Name Lookup (as per used as a domain name to be processed by Domain Name Lookup (as per
[RFC5891]), an alternative method MAY be used, converting <ireg-name> [RFC5891]), an alternative method MAY be used, converting <ireg-name>
as follows: as follows:
If there are any sequences of <pct-encoded>, and their corresponding If there is any percent-encoding, and the corresponding octets all
octets all represent valid UTF-8 octet sequences, then convert these represent valid UTF-8 octet sequences, then convert these back to
back to Unicode character sequences. (If any <pct-encoded> sequences Unicode character sequences. (If any percent-encodings are not valid
are not valid UTF-8 octet sequences, then leave the entire field as UTF-8 octet sequences, then leave the entire field as is without any
is without any change, since punycode encoding would not succeed.) change, since punycode encoding would not succeed.)
Replace the ireg-name part of the IRI by the part converted using the Replace the ireg-name part of the IRI by the part converted using the
Domain Name Lookup procedure (Subsections 5.3 to 5.5) of [RFC5891]. Domain Name Lookup procedure (Subsections 5.3 to 5.5) of [RFC5891].
on each dot-separated label, and by using U+002E (FULL STOP) as a on each dot-separated label, and by using U+002E (FULL STOP) as a
label separator. This procedure may fail, but this would mean that label separator. This procedure may fail, but this would mean that
the IRI cannot be resolved. In such cases, if the domain name the IRI cannot be resolved. In such cases, if the domain name
conversion fails, then the entire IRI conversion fails. Processors conversion fails, then the entire IRI conversion fails. Processors
that have no mechanism for signalling a failure MAY instead that have no mechanism for signalling a failure MAY instead
substitute an otherwise invalid host name, although such processing substitute an otherwise invalid host name, although such processing
SHOULD be avoided. SHOULD be avoided.
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For example, the IRI For example, the IRI
"http://r&#xE9;sum&#xE9;.example.org" "http://r&#xE9;sum&#xE9;.example.org"
is converted to is converted to
"http://xn--rsum-bad.example.org". "http://xn--rsum-bad.example.org".
This conversion for ireg-name will be better able to deal with legacy This conversion for ireg-name will be better able to deal with legacy
infrastructure that cannot handle percent-encoding in domain names. infrastructure that cannot handle percent-encoding in domain names.
3.4.3. Additional Considerations 3.4.3. Additional Considerations
Note: Domain Names may appear in parts of an IRI other than the Domain Names can appear in parts of an IRI other than the ireg-name
ireg-name part. It is the responsibility of scheme-specific part. It is the responsibility of scheme-specific implementations
implementations (if the Internationalized Domain Name is part of (if the Internationalized Domain Name is part of the scheme syntax)
the scheme syntax) or of server-side implementations (if the or of server-side implementations (if the Internationalized Domain
Internationalized Domain Name is part of 'iquery') to apply the Name is part of 'iquery') to apply the necessary conversions at the
necessary conversions at the appropriate point. Example: Trying appropriate point. Example: Trying to validate the Web page at
to validate the Web page at http://r&#xE9;sum&#xE9;.example.org would lead to an IRI of
http://r&#xE9;sum&#xE9;.example.org would lead to an IRI of http://validator.w3.org/check?uri=http%3A%2F%2Fr&#xE9;sum&#xE9;
http://validator.w3.org/check?uri=http%3A%2F%2Fr&#xE9;sum&#xE9; .example.org, which would convert to a URI of
.example.org, which would convert to a URI of http://validator.w3.org/check?uri=http%3A%2F%2Fr%C3%A9sum%C3%A9.
http://validator.w3.org/check?uri=http%3A%2F%2Fr%C3%A9sum%C3%A9. example.org. The server-side implementation is responsible for
example.org. The server-side implementation is responsible for making the necessary conversions to be able to retrieve the Web page.
making the necessary conversions to be able to retrieve the Web
page.
Note: In this process, characters allowed in URI references and In this process, characters allowed in URI references and existing
existing percent-encoded sequences are not encoded further. (This percent-encoded sequences are not encoded further. (This mapping is
mapping is similar to, but different from, the encoding applied similar to, but different from, the encoding applied when arbitrary
when arbitrary content is included in some part of a URI.) For content is included in some part of a URI.) For example, an IRI of
example, an IRI of "http://www.example.org/red%09ros&#xE9;#red" (in XML notation) is
"http://www.example.org/red%09ros&#xE9;#red" (in XML notation) is converted to
converted to "http://www.example.org/red%09ros%C3%A9#red", not to something like
"http://www.example.org/red%09ros%C3%A9#red", not to something "http%3A%2F%2Fwww.example.org%2Fred%2509ros%C3%A9%23red".
like
"http%3A%2F%2Fwww.example.org%2Fred%2509ros%C3%A9%23red".
3.5. Mapping query components 3.5. Mapping query components
For compatibility with existing deployed HTTP infrastructure, the For compatibility with existing deployed HTTP infrastructure, the
following special case applies for the schemes "http" and "https" following special case applies for the schemes "http" and "https"
when an IRI is found in a document whose charset is not based on UCS when an IRI is found in a document whose charset is not based on UCS
(e.g., not UTF-8 or UTF-16). In such a case, the "query" component (e.g., not UTF-8 or UTF-16). In such a case, the "query" component
of an IRI is mapped into a URI by using the document charset rather of an IRI is mapped into a URI by using the document charset rather
than UTF-8 as the binary representation before pct-encoding. This than UTF-8 as the binary representation before percent-encoding.
mapping is not applied for any other scheme or component. This mapping is not applied for any other schemes or components.
3.6. Mapping IRIs to URIs 3.6. Mapping IRIs to URIs
The mapping from an IRI to URI is accomplished by applying the The mapping from an IRI to URI is accomplished by applying the
mapping above (from IRI to URI components) and then reassembling a mapping above (from IRI to URI components) and then reassembling a
URI from the parsed URI components using the original punctuation URI from the parsed URI components using the original punctuation
that delimited the IRI components. that delimited the IRI components.
4. Converting URIs to IRIs 4. Converting URIs to IRIs
In some situations, for presentation and further processing, it is In some situations, for presentation and further processing, it is
desirable to convert a URI into an equivalent IRI without unnecessary desirable to convert a URI into an equivalent IRI without unnecessary
percent encoding. Of course, every URI is already an IRI in its own percent encoding. Of course, every URI is already an IRI in its own
right without any conversion. This section gives one possible right without any conversion. This section gives one possible
procedure for URI to IRI mapping. procedure for converting a URI to an IRI.
4.1. Limitations
The conversion described in this section, if given a valid URI, will The conversion described in this section, if given a valid URI, will
result in an IRI that maps back to the URI used as an input for the result in an IRI that maps back to the URI used as an input for the
conversion (except for potential case differences in percent-encoding conversion (except for potential case differences in percent-encoding
and for potential percent-encoded unreserved characters). However, and for potential percent-encoded unreserved characters). However,
the IRI resulting from this conversion may differ from the original the IRI resulting from this conversion may differ from the original
IRI (if there ever was one). IRI (if there ever was one).
URI-to-IRI conversion removes percent-encodings, but not all percent- URI-to-IRI conversion removes percent-encodings, but not all percent-
encodings can be eliminated. There are several reasons for this: encodings can be eliminated. There are several reasons for this:
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1. Some percent-encodings are necessary to distinguish percent- 1. Some percent-encodings are necessary to distinguish percent-
encoded and unencoded uses of reserved characters. encoded and unencoded uses of reserved characters.
2. Some percent-encodings cannot be interpreted as sequences of UTF-8 2. Some percent-encodings cannot be interpreted as sequences of UTF-8
octets. octets.
(Note: The octet patterns of UTF-8 are highly regular. Therefore, (Note: The octet patterns of UTF-8 are highly regular. Therefore,
there is a very high probability, but no guarantee, that percent- there is a very high probability, but no guarantee, that percent-
encodings that can be interpreted as sequences of UTF-8 octets encodings that can be interpreted as sequences of UTF-8 octets
actually originated from UTF-8. For a detailed discussion, see actually originated from UTF-8. For a detailed discussion, see
[Duerst97].) [Duerst97].)
3. The conversion may result in a character that is not appropriate 3. The conversion may result in a character that is not appropriate
in an IRI. See Section 2.2, and Section 5.1 for further details. in an IRI. See Section 2.2, and Section 5.1 for further details.
4. IRI to URI conversion has different rules for dealing with domain 4. As described in Section 3.5, IRI to URI conversion may work
names and query parameters. somewhat differently for query components.
4.2. Conversion
Conversion from a URI to an IRI MAY be done by using the following Conversion from a URI to an IRI MAY be done by using the following
steps: steps:
1. Represent the URI as a sequence of octets in US-ASCII. 1. Represent the URI as a sequence of octets in US-ASCII.
2. Convert all percent-encodings ("%" followed by two hexadecimal 2. Convert all percent-encodings ("%" followed by two hexadecimal
digits) to the corresponding octets, except those corresponding to digits) to the corresponding octets, except those corresponding to
"%", characters in "reserved", and characters in US-ASCII not "%", characters in "reserved", and characters in US-ASCII not
allowed in URIs. allowed in URIs.
3. Re-percent-encode any octet produced in step 2 that is not part of 3. Re-percent-encode any octet produced in step 2 that is not part of
a strictly legal UTF-8 octet sequence. a strictly legal UTF-8 octet sequence.
4. Re-percent-encode all octets produced in step 3 that in UTF-8 4. Re-percent-encode all octets produced in step 3 that in UTF-8
represent characters that are not appropriate according to represent characters that are not appropriate according to
Section 2.2 and Section 5.1. Section 2.2 and Section 5.1.
5. Interpret the resulting octet sequence as a sequence of characters 5. Optionally, re-percent-encode octets in the query component if the
scheme is one of those mentioned in Section 3.5.
6. Interpret the resulting octet sequence as a sequence of characters
encoded in UTF-8. encoded in UTF-8.
6. URIs known to contain domain names in the reg-name component 7. URIs known to contain domain names in the reg-name component
SHOULD convert punycode-encoded domain name labels to the SHOULD convert punycode-encoded domain name labels to the
corresponding characters using the ToUnicode procedure. corresponding characters using the ToUnicode procedure.
This procedure will convert as many percent-encoded characters as This procedure will convert as many percent-encoded characters as
possible to characters in an IRI. Because there are some choices possible to characters in an IRI. Because there are some choices in
when step 4 is applied (see Section 5.1), results may vary. steps 4 (see also Section 5.1) and 5, results may vary.
Conversions from URIs to IRIs MUST NOT use any character encoding Conversions from URIs to IRIs MUST NOT use any character encoding
other than UTF-8 in steps 3 and 4, even if it might be possible to other than UTF-8 in steps 3 and 4, even if it might be possible to
guess from the context that another character encoding than UTF-8 was guess from the context that another character encoding than UTF-8 was
used in the URI. For example, the URI used in the URI. For example, the URI
"http://www.example.org/r%E9sum%E9.html" might with some guessing be "http://www.example.org/r%E9sum%E9.html" might with some guessing be
interpreted to contain two e-acute characters encoded as iso-8859-1. interpreted to contain two e-acute characters encoded as iso-8859-1.
It must not be converted to an IRI containing these e-acute It must not be converted to an IRI containing these e-acute
characters. Otherwise, in the future the IRI will be mapped to characters. Otherwise, in the future the IRI will be mapped to
"http://www.example.org/r%C3%A9sum%C3%A9.html", which is a different "http://www.example.org/r%C3%A9sum%C3%A9.html", which is a different
URI from "http://www.example.org/r%E9sum%E9.html". URI from "http://www.example.org/r%E9sum%E9.html".
4.1. Examples 4.3. Examples
This section shows various examples of converting URIs to IRIs. Each This section shows various examples of converting URIs to IRIs. Each
example shows the result after each of the steps 1 through 6 is example shows the result after each of the steps 1 through 6 is
applied. XML Notation is used for the final result. Octets are applied. XML Notation is used for the final result. Octets are
denoted by "<" followed by two hexadecimal digits followed by ">". denoted by "<" followed by two hexadecimal digits followed by ">".
The following example contains the sequence "%C3%BC", which is a The following example contains the sequence "%C3%BC", which is a
strictly legal UTF-8 sequence, and which is converted into the actual strictly legal UTF-8 sequence, and which is converted into the actual
character U+00FC, LATIN SMALL LETTER U WITH DIAERESIS (also known as character U+00FC, LATIN SMALL LETTER U WITH DIAERESIS (also known as
u-umlaut). u-umlaut).
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parse and process the '/' separately. parse and process the '/' separately.
d. The ZERO WIDTH NON-JOINER (U+200C) and ZERO WIDTH JOINER (U+200D) d. The ZERO WIDTH NON-JOINER (U+200C) and ZERO WIDTH JOINER (U+200D)
are invisible in most contexts, but are crucial in some very are invisible in most contexts, but are crucial in some very
limited contexts. Appendix A of [RFC5892] contains contextual limited contexts. Appendix A of [RFC5892] contains contextual
restrictions for these and some other characters. The use of restrictions for these and some other characters. The use of
these characters are strongly discouraged except in the relevant these characters are strongly discouraged except in the relevant
contexts. contexts.
Additional information is available from [UNIXML]. [UNIXML] is Additional information is available from [UNIXML]. [UNIXML] is
written in the context of running text rather than in that of written in the context of general purpose text rather than in that of
identifiers. Nevertheless, it discusses many of the categories of identifiers. Nevertheless, it discusses many of the categories of
characters not appropriate for IRIs. characters not appropriate for IRIs.
5.2. Software Interfaces and Protocols 5.2. Software Interfaces and Protocols
Although an IRI is defined as a sequence of characters, software Although an IRI is defined as a sequence of characters, software
interfaces for URIs typically function on sequences of octets or interfaces for URIs typically function on sequences of octets or
other kinds of code units. Thus, software interfaces and protocols other kinds of code units. Thus, software interfaces and protocols
MUST define which character encoding is used. MUST define which character encoding is used.
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This section discusses details and gives examples for point c) in This section discusses details and gives examples for point c) in
Section 1.2. To be able to use IRIs, the URI corresponding to the Section 1.2. To be able to use IRIs, the URI corresponding to the
IRI in question has to encode original characters into octets by IRI in question has to encode original characters into octets by
using UTF-8. This can be specified for all URIs of a URI scheme or using UTF-8. This can be specified for all URIs of a URI scheme or
can apply to individual URIs for schemes that do not specify how to can apply to individual URIs for schemes that do not specify how to
encode original characters. It can apply to the whole URI, or only encode original characters. It can apply to the whole URI, or only
to some part. For background information on encoding characters into to some part. For background information on encoding characters into
URIs, see also Section 2.5 of [RFC3986]. URIs, see also Section 2.5 of [RFC3986].
For new URI schemes, using UTF-8 is recommended in [RFC4395bis]. For new URI/IRI schemes, using UTF-8 is recommended in [RFC4395bis].
Examples where UTF-8 is already used are the URN syntax [RFC2141], Examples where UTF-8 is already used are the URN syntax [RFC2141],
IMAP URLs [RFC2192], POP URLs [RFC2384], XMPP URLs [RFC5122], and the IMAP URLs [RFC2192], POP URLs [RFC2384], XMPP URLs [RFC5122], and the
'mailto:' scheme [RFC6068]. On the other hand, because the HTTP URI 'mailto:' scheme [RFC6068]. On the other hand, because the HTTP URI
scheme does not specify how to encode original characters, only some scheme does not specify how to encode original characters, only some
HTTP URLs can have corresponding but different IRIs. HTTP URLs can have corresponding but different IRIs.
For example, for a document with a URI of For example, for a document with a URI of
"http://www.example.org/r%C3%A9sum%C3%A9.html", it is possible to "http://www.example.org/r%C3%A9sum%C3%A9.html", it is possible to
construct a corresponding IRI (in XML notation, see Section 1.4): construct a corresponding IRI (in XML notation, see Section 1.4):
"http://www.example.org/r&#xE9;sum&#xE9;.html" ("&#xE9;" stands for "http://www.example.org/r&#xE9;sum&#xE9;.html" ("&#xE9;" stands for
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IRI, as the percent-encoding is not based on UTF-8. IRI, as the percent-encoding is not based on UTF-8.
For most URI schemes, there is no need to upgrade their scheme For most URI schemes, there is no need to upgrade their scheme
definition in order for them to work with IRIs. The main case where definition in order for them to work with IRIs. The main case where
upgrading makes sense is when a scheme definition, or a particular upgrading makes sense is when a scheme definition, or a particular
component of a scheme, is strictly limited to the use of US-ASCII component of a scheme, is strictly limited to the use of US-ASCII
characters with no provision to include non-ASCII characters/octets characters with no provision to include non-ASCII characters/octets
via percent-encoding, or if a scheme definition currently uses highly via percent-encoding, or if a scheme definition currently uses highly
scheme-specific provisions for the encoding of non-ASCII characters. scheme-specific provisions for the encoding of non-ASCII characters.
This specification updates the IANA registry of URI schemes to note
their applicability to IRIs, see Section 8. All IRIs use URI
schemes, and all URIs with URI schemes can be used as IRIs, even
though in some cases only by using URIs directly as IRIs, without any
conversion.
Scheme definitions can impose restrictions on the syntax of scheme- Scheme definitions can impose restrictions on the syntax of scheme-
specific URIs; i.e., URIs that are admissible under the generic URI specific URIs; i.e., URIs that are admissible under the generic URI
syntax [RFC3986] may not be admissible due to narrower syntactic syntax [RFC3986] may not be admissible due to narrower syntactic
constraints imposed by a URI scheme specification. URI scheme constraints imposed by a URI scheme specification. URI scheme
definitions cannot broaden the syntactic restrictions of the generic definitions cannot broaden the syntactic restrictions of the generic
URI syntax; otherwise, it would be possible to generate URIs that URI syntax; otherwise, it would be possible to generate URIs that
satisfied the scheme-specific syntactic constraints without satisfied the scheme-specific syntactic constraints without
satisfying the syntactic constraints of the generic URI syntax. satisfying the syntactic constraints of the generic URI syntax.
However, additional syntactic constraints imposed by URI scheme However, additional syntactic constraints imposed by URI scheme
specifications are applicable to IRI, as the corresponding URI specifications are applicable to IRI, as the corresponding URI
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For reference, we here also list the code points and code units not For reference, we here also list the code points and code units not
even allowed in Legacy Extended IRIs: even allowed in Legacy Extended IRIs:
Surrogate code units (D800-DFFF): These do not represent Unicode Surrogate code units (D800-DFFF): These do not represent Unicode
codepoints. codepoints.
Non-characters (U+FFFE-FFFF): These are not allowed in XML nor Non-characters (U+FFFE-FFFF): These are not allowed in XML nor
LEIRIs. LEIRIs.
7. URI/IRI Processing Guidelines (Informative) 7. Processing of URIs/IRIs/URLs by Web Browsers
For legacy reasons, many web browsers exhibit some irregularities
when processing URIs, IRIs, and URLs. This is being documented in
[HTMLURL], in the hope that it will lead to more uniform
implementations of these irregularities across web browsers.
As far as currently known, creators of content for web browsers (such
as HTML) can use all URIs without problems. They can also use all
IRIs without problems except that they should be aware of the fact
that query parts for HTTP/HTTPS IRIs should be percent-escaped.
8. URI/IRI Processing Guidelines (Informative)
This informative section provides guidelines for supporting IRIs in This informative section provides guidelines for supporting IRIs in
the same software components and operations that currently process the same software components and operations that currently process
URIs: Software interfaces that handle URIs, software that allows URIs: Software interfaces that handle URIs, software that allows
users to enter URIs, software that creates or generates URIs, users to enter URIs, software that creates or generates URIs,
software that displays URIs, formats and protocols that transport software that displays URIs, formats and protocols that transport
URIs, and software that interprets URIs. These may all require URIs, and software that interprets URIs. These may all require
modification before functioning properly with IRIs. The modification before functioning properly with IRIs. The
considerations in this section also apply to URI references and IRI considerations in this section also apply to URI references and IRI
references. references.
7.1. URI/IRI Software Interfaces 8.1. URI/IRI Software Interfaces
Software interfaces that handle URIs, such as URI-handling APIs and Software interfaces that handle URIs, such as URI-handling APIs and
protocols transferring URIs, need interfaces and protocol elements protocols transferring URIs, need interfaces and protocol elements
that are designed to carry IRIs. that are designed to carry IRIs.
In case the current handling in an API or protocol is based on US- In case the current handling in an API or protocol is based on US-
ASCII, UTF-8 is recommended as the character encoding for IRIs, as it ASCII, UTF-8 is recommended as the character encoding for IRIs, as it
is compatible with US-ASCII, is in accordance with the is compatible with US-ASCII, is in accordance with the
recommendations of [RFC2277], and makes converting to URIs easy. In recommendations of [RFC2277], and makes converting to URIs easy. In
any case, the API or protocol definition must clearly define the any case, the API or protocol definition must clearly define the
character encoding to be used. character encoding to be used.
The transfer from URI-only to IRI-capable components requires no The transfer from URI-only to IRI-capable components requires no
mapping, although the conversion described in Section 4 above may be mapping, although the conversion described in Section 4 above may be
performed. It is preferable not to perform this inverse conversion performed. It is preferable not to perform this inverse conversion
unless it is certain this can be done correctly. unless it is certain this can be done correctly.
7.2. URI/IRI Entry 8.2. URI/IRI Entry
Some components allow users to enter URIs into the system by typing Some components allow users to enter URIs into the system by typing
or dictation, for example. This software must be updated to allow or dictation, for example. This software must be updated to allow
for IRI entry. for IRI entry.
A person viewing a visual presentation of an IRI (as a sequence of A person viewing a visual presentation of an IRI (as a sequence of
glyphs, in some order, in some visual display) will use an entry glyphs, in some order, in some visual display) will use an entry
method for characters in the user's language to input the IRI. method for characters in the user's language to input the IRI.
Depending on the script and the input method used, this may be a more Depending on the script and the input method used, this may be a more
or less complicated process. or less complicated process.
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viewing an IRI as mapped to a URI. This will help users when some of viewing an IRI as mapped to a URI. This will help users when some of
the software they use does not yet accept IRIs. the software they use does not yet accept IRIs.
An IRI input component interfacing to components that handle URIs, An IRI input component interfacing to components that handle URIs,
but not IRIs, must map the IRI to a URI before passing it to these but not IRIs, must map the IRI to a URI before passing it to these
components. components.
For the input of IRIs with right-to-left characters, please see For the input of IRIs with right-to-left characters, please see
[Bidi]. [Bidi].
7.3. URI/IRI Transfer between Applications 8.3. URI/IRI Transfer between Applications
Many applications (for example, mail user agents) try to detect URIs Many applications (for example, mail user agents) try to detect URIs
appearing in plain text. For this, they use some heuristics based on appearing in plain text. For this, they use some heuristics based on
URI syntax. They then allow the user to click on such URIs and URI syntax. They then allow the user to click on such URIs and
retrieve the corresponding resource in an appropriate (usually retrieve the corresponding resource in an appropriate (usually
scheme-dependent) application. scheme-dependent) application.
Such applications would need to be upgraded, in order to use the IRI Such applications would need to be upgraded, in order to use the IRI
syntax as a base for heuristics. In particular, a non-ASCII syntax as a base for heuristics. In particular, a non-ASCII
character should not be taken as the indication of the end of an IRI. character should not be taken as the indication of the end of an IRI.
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by the system-wide IRI invocation mechanism, or to a URI (according by the system-wide IRI invocation mechanism, or to a URI (according
to Section 3.6) if the system-wide invocation mechanism only accepts to Section 3.6) if the system-wide invocation mechanism only accepts
URIs. URIs.
The clipboard is another frequently used way to transfer URIs and The clipboard is another frequently used way to transfer URIs and
IRIs from one application to another. On most platforms, the IRIs from one application to another. On most platforms, the
clipboard is able to store and transfer text in many languages and clipboard is able to store and transfer text in many languages and
scripts. Correctly used, the clipboard transfers characters, not scripts. Correctly used, the clipboard transfers characters, not
octets, which will do the right thing with IRIs. octets, which will do the right thing with IRIs.
7.4. URI/IRI Generation 8.4. URI/IRI Generation
Systems that offer resources through the Internet, where those Systems that offer resources through the Internet, where those
resources have logical names, sometimes automatically generate URIs resources have logical names, sometimes automatically generate URIs
for the resources they offer. For example, some HTTP servers can for the resources they offer. For example, some HTTP servers can
generate a directory listing for a file directory and then respond to generate a directory listing for a file directory and then respond to
the generated URIs with the files. the generated URIs with the files.
Many legacy character encodings are in use in various file systems. Many legacy character encodings are in use in various file systems.
Many currently deployed systems do not transform the local character Many currently deployed systems do not transform the local character
representation of the underlying system before generating URIs. representation of the underlying system before generating URIs.
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identifiers should make the appropriate transformations. For identifiers should make the appropriate transformations. For
example, if a file system contains a file named "r&#xE9;sum&# example, if a file system contains a file named "r&#xE9;sum&#
xE9;.html", a server should expose this as "r%C3%A9sum%C3%A9.html" in xE9;.html", a server should expose this as "r%C3%A9sum%C3%A9.html" in
a URI, which allows use of "r&#xE9;sum&#xE9;.html" in an IRI, even if a URI, which allows use of "r&#xE9;sum&#xE9;.html" in an IRI, even if
locally the file name is kept in a character encoding other than locally the file name is kept in a character encoding other than
UTF-8. UTF-8.
This recommendation particularly applies to HTTP servers. For FTP This recommendation particularly applies to HTTP servers. For FTP
servers, similar considerations apply; see [RFC2640]. servers, similar considerations apply; see [RFC2640].
7.5. URI/IRI Selection 8.5. URI/IRI Selection
In some cases, resource owners and publishers have control over the In some cases, resource owners and publishers have control over the
IRIs used to identify their resources. This control is mostly IRIs used to identify their resources. This control is mostly
executed by controlling the resource names, such as file names, executed by controlling the resource names, such as file names,
directly. directly.
In these cases, it is recommended to avoid choosing IRIs that are In these cases, it is recommended to avoid choosing IRIs that are
easily confused. For example, for US-ASCII, the lower-case ell ("l") easily confused. For example, for US-ASCII, the lower-case ell ("l")
is easily confused with the digit one ("1"), and the upper-case oh is easily confused with the digit one ("1"), and the upper-case oh
("O") is easily confused with the digit zero ("0"). Publishers ("O") is easily confused with the digit zero ("0"). Publishers
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the Latin "A", the Greek "Alpha", and the Cyrillic "A". To avoid the Latin "A", the Greek "Alpha", and the Cyrillic "A". To avoid
such cases, IRIs should only be created where all the characters in a such cases, IRIs should only be created where all the characters in a
single component are used together in a given language. This usually single component are used together in a given language. This usually
means that all of these characters will be from the same script, but means that all of these characters will be from the same script, but
there are languages that mix characters from different scripts (such there are languages that mix characters from different scripts (such
as Japanese). This is similar to the heuristics used to distinguish as Japanese). This is similar to the heuristics used to distinguish
between letters and numbers in the examples above. Also, for Latin, between letters and numbers in the examples above. Also, for Latin,
Greek, and Cyrillic, using lowercase letters results in fewer Greek, and Cyrillic, using lowercase letters results in fewer
ambiguities than using uppercase letters would. ambiguities than using uppercase letters would.
7.6. Display of URIs/IRIs 8.6. Display of URIs/IRIs
In situations where the rendering software is not expected to display In situations where the rendering software is not expected to display
non-ASCII parts of the IRI correctly using the available layout and non-ASCII parts of the IRI correctly using the available layout and
font resources, these parts should be percent-encoded before being font resources, these parts should be percent-encoded before being
displayed. displayed.
For display of Bidi IRIs, please see [Bidi]. For display of Bidi IRIs, please see [Bidi].
7.7. Interpretation of URIs and IRIs 8.7. Interpretation of URIs and IRIs
Software that interprets IRIs as the names of local resources should Software that interprets IRIs as the names of local resources should
accept IRIs in multiple forms and convert and match them with the accept IRIs in multiple forms and convert and match them with the
appropriate local resource names. appropriate local resource names.
First, multiple representations include both IRIs in the native First, multiple representations include both IRIs in the native
character encoding of the protocol and also their URI counterparts. character encoding of the protocol and also their URI counterparts.
Second, it may include URIs constructed based on character encodings Second, it may include URIs constructed based on character encodings
other than UTF-8. These URIs may be produced by user agents that do other than UTF-8. These URIs may be produced by user agents that do
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beyond the US-ASCII repertoire, this may, for example, include beyond the US-ASCII repertoire, this may, for example, include
ignoring the accents on received IRIs or resource names. Please note ignoring the accents on received IRIs or resource names. Please note
that such mappings, including case mappings, are language dependent. that such mappings, including case mappings, are language dependent.
It can be difficult to identify a resource unambiguously if too many It can be difficult to identify a resource unambiguously if too many
mappings are taken into consideration. However, percent-encoded and mappings are taken into consideration. However, percent-encoded and
not percent-encoded parts of IRIs can always be clearly not percent-encoded parts of IRIs can always be clearly
distinguished. Also, the regularity of UTF-8 (see [Duerst97]) makes distinguished. Also, the regularity of UTF-8 (see [Duerst97]) makes
the potential for collisions lower than it may seem at first. the potential for collisions lower than it may seem at first.
7.8. Upgrading Strategy 8.8. Upgrading Strategy
Where this recommendation places further constraints on software for Where this recommendation places further constraints on software for
which many instances are already deployed, it is important to which many instances are already deployed, it is important to
introduce upgrades carefully and to be aware of the various introduce upgrades carefully and to be aware of the various
interdependencies. interdependencies.
If IRIs cannot be interpreted correctly, they should not be created, If IRIs cannot be interpreted correctly, they should not be created,
generated, or transported. This suggests that upgrading URI generated, or transported. This suggests that upgrading URI
interpreting software to accept IRIs should have highest priority. interpreting software to accept IRIs should have highest priority.
skipping to change at page 31, line 9 skipping to change at page 31, line 9
encoding of the form page, the returned query URIs will use UTF-8 as encoding of the form page, the returned query URIs will use UTF-8 as
the character encoding (unless the user, for whatever reason, changes the character encoding (unless the user, for whatever reason, changes
the character encoding) and will therefore be compatible with IRIs. the character encoding) and will therefore be compatible with IRIs.
These recommendations, when taken together, will allow for the These recommendations, when taken together, will allow for the
extension from URIs to IRIs in order to handle characters other than extension from URIs to IRIs in order to handle characters other than
US-ASCII while minimizing interoperability problems. For US-ASCII while minimizing interoperability problems. For
considerations regarding the upgrade of URI scheme definitions, see considerations regarding the upgrade of URI scheme definitions, see
Section 5.4. Section 5.4.
8. IANA Considerations 9. IANA Considerations
NOTE: THIS SECTION NEEDS REVIEW AGAINST HAPPIANA WORK.
RFC Editor and IANA note: Please Replace RFC XXXX with the number of
this document when it issues as an RFC, and RFC YYYY with the number
of the RFC issued for draft-ietf-iri-rfc3987bis.
IANA maintains a registry of "URI schemes". This document attempts
to make it clear from the registry that a "URI scheme" also serves an
"IRI scheme", and makes several changes to the registry.
The description of the registry should be changed: "RFC 4395 defined
an IANA-maintained registry of URI Schemes. RFC XXXX updates this
registry to make it clear that the registered values also serve as
IRI schemes, as defined in RFC YYYY."
The registry includes schemes marked as Permanent or Provisional. This specification does not affect IANA. For details on how to
Previously, this was accomplished by having two sections, "Permanent" define a URI/IRI scheme and register it with IANA, see [RFC4395bis].
and "Provisional". However, in order to allow other status
("Historical", and possibly a Proposed status for proposals which
have been received but not accepted), the registry should be changed
so that the status is indicated in a separate "Status" column, whose
values may be "Permanent", "Provisional" or "Historical". Changes in
status as well as updates to the entire registration may be
accomplished by requests and expert review.
9. Security Considerations 10. Security Considerations
The security considerations discussed in [RFC3986] also apply to The security considerations discussed in [RFC3986] also apply to
IRIs. In addition, the following issues require particular care for IRIs. In addition, the following issues require particular care for
IRIs. IRIs.
Incorrect encoding or decoding can lead to security problems. For Incorrect encoding or decoding can lead to security problems. For
example, some UTF-8 decoders do not check against overlong byte example, some UTF-8 decoders do not check against overlong byte
sequences. See [UTR36] Section 3 for details. sequences. See [UTR36] Section 3 for details.
There are serious difficulties with relying on a human to verify that There are serious difficulties with relying on a human to verify that
skipping to change at page 32, line 27 skipping to change at page 32, line 5
normalization expectations, use of percent-encoding with various normalization expectations, use of percent-encoding with various
legacy encodings, and bidirectionality issues. See also [Bidi]. legacy encodings, and bidirectionality issues. See also [Bidi].
Confusion can occur in various IRI components, such as the domain Confusion can occur in various IRI components, such as the domain
name part or the path part, or between IRI components. For name part or the path part, or between IRI components. For
considerations specific to the domain name part, see [RFC5890]. For considerations specific to the domain name part, see [RFC5890]. For
considerations specific to particular protocols or schemes, see the considerations specific to particular protocols or schemes, see the
security sections of the relevant specifications and registration security sections of the relevant specifications and registration
templates. Administrators of sites that allow independent users to templates. Administrators of sites that allow independent users to
create resources in the same sub area have to be careful. Details create resources in the same sub area have to be careful. Details
are discussed in Section 7.5. are discussed in Section 8.5.
The characters additionally allowed in Legacy Extended IRIs introduce The characters additionally allowed in Legacy Extended IRIs introduce
additional security issues. For details, see Section 6.3. additional security issues. For details, see Section 6.3.
10. Acknowledgements 11. Acknowledgements
This document was derived from [RFC3987]; the acknowledgments from This document was derived from [RFC3987]; the acknowledgments from
that specification still apply. that specification still apply.
In addition, this document was influenced by contributions from (in In addition, this document was influenced by contributions from (in
no particular order) Norman Walsh, Richard Tobin, Henry S. Thomson, no particular order) Norman Walsh, Richard Tobin, Henry S. Thomson,
John Cowan, Paul Grosso, the XML Core Working Group of the W3C, Chris John Cowan, Paul Grosso, the XML Core Working Group of the W3C, Chris
Lilley, Bjoern Hoehrmann, Felix Sasaki, Jeremy Carroll, Frank Lilley, Bjoern Hoehrmann, Felix Sasaki, Jeremy Carroll, Frank
Ellermann, Michael Everson, Cary Karp, Matitiahu Allouche, Richard Ellermann, Michael Everson, Cary Karp, Matitiahu Allouche, Richard
Ishida, Addison Phillips, Jonathan Rosenne, Najib Tounsi, Debbie Ishida, Addison Phillips, Jonathan Rosenne, Najib Tounsi, Debbie
skipping to change at page 33, line 7 skipping to change at page 32, line 32
Roessler, Lisa Dusseault, Julian Reschke, Giovanni Campagna, Anne van Roessler, Lisa Dusseault, Julian Reschke, Giovanni Campagna, Anne van
Kesteren, Mark Nottingham, Erik van der Poel, Marcin Hanclik, Marcos Kesteren, Mark Nottingham, Erik van der Poel, Marcin Hanclik, Marcos
Caceres, Roy Fielding, Greg Wilkins, Pieter Hintjens, Daniel R. Caceres, Roy Fielding, Greg Wilkins, Pieter Hintjens, Daniel R.
Tobias, Marko Martin, Maciej Stanchowiak, Wil Tan, Yui Naruse, Tobias, Marko Martin, Maciej Stanchowiak, Wil Tan, Yui Naruse,
Michael A. Puls II, Dave Thaler, Tom Petch, John Klensin, Shawn Michael A. Puls II, Dave Thaler, Tom Petch, John Klensin, Shawn
Steele, Peter Saint-Andre, Geoffrey Sneddon, Chris Weber, Alex Steele, Peter Saint-Andre, Geoffrey Sneddon, Chris Weber, Alex
Melnikov, Slim Amamou, S. Moonesamy, Tim Berners-Lee, Yaron Goland, Melnikov, Slim Amamou, S. Moonesamy, Tim Berners-Lee, Yaron Goland,
Sam Ruby, Adam Barth, Abdulrahman I. ALGhadir, Aharon Lanin, Thomas Sam Ruby, Adam Barth, Abdulrahman I. ALGhadir, Aharon Lanin, Thomas
Milo, Murray Sargent, Marc Blanchet, and Mykyta Yevstifeyev. Milo, Murray Sargent, Marc Blanchet, and Mykyta Yevstifeyev.
11. Main Changes Since RFC 3987 Anne van Kesteren is also gratefully acknowledged for his ongoing
work documenting browser behavior with respect to URIs/URIs/URLs (see
[HTMLURL]).
12. Main Changes Since RFC 3987
This section describes the main changes since [RFC3987]. This section describes the main changes since [RFC3987].
11.1. Split out Bidi, processing guidelines, comparison sections 12.1. Split out Bidi, processing guidelines, comparison sections
Move some components (comparison, bidi, processing) into separate Move some components (comparison, bidi, processing) into separate
documents. documents.
11.2. Major restructuring of IRI processing model 12.2. Major restructuring of IRI processing model
Major restructuring of IRI processing model to make scheme-specific Major restructuring of IRI processing model to make scheme-specific
translation necessary to handle IDNA requirements and for consistency translation necessary to handle IDNA requirements and for consistency
with web implementations. with web implementations.
Starting with IRI, you want one of: Starting with IRI, you want one of:
a IRI components (IRI parsed into UTF8 pieces) a IRI components (IRI parsed into UTF8 pieces)
b URI components (URI parsed into ASCII pieces, encoded correctly) b URI components (URI parsed into ASCII pieces, encoded correctly)
c whole URI (for passing on to some other system that wants whole c whole URI (for passing on to some other system that wants whole
URIs) URIs)
11.2.1. OLD WAY 12.2.1. OLD WAY
1. Pct-encoding on the whole thing to a URI. (c1) If you want a 1. Percent-encoding on the whole thing to a URI. (c1) If you want a
(maybe broken) whole URI, you might stop here. (maybe broken) whole URI, you might stop here.
2. Parsing the URI into URI components. (b1) If you want (maybe 2. Parsing the URI into URI components. (b1) If you want (maybe
broken) URI components, stop here. broken) URI components, stop here.
3. Decode the components (undoing the pct-encoding). (a) if you want 3. Decode the components (undoing the percent-encoding). (a) if you
IRI components, stop here. want IRI components, stop here.
4. reencode: Either using a different encoding some components (for 4. reencode: Either using a different encoding some components (for
domain names, and query components in web pages, which depends on domain names, and query components in web pages, which depends on
the component, scheme and context), and otherwise using pct- the component, scheme and context), and otherwise using percent-
encoding. (b2) if you want (good) URI components, stop here. encoding. (b2) if you want (good) URI components, stop here.
5. reassemble the reencoded components. (c2) if you want a (*good*) 5. reassemble the reencoded components. (c2) if you want a (*good*)
whole URI stop here. whole URI stop here.
11.2.2. NEW WAY 12.2.2. NEW WAY
1. Parse the IRI into IRI components using the generic syntax. (a) 1. Parse the IRI into IRI components using the generic syntax. (a)
if you want IRI components, stop here. if you want IRI components, stop here.
2. Encode each components, using pct-encoding, IDN encoding, or 2. Encode each components, using percent-encoding, IDN encoding, or
special query part encoding depending on the component scheme or special query part encoding depending on the component scheme or
context. (b) If you want URI components, stop here. context. (b) If you want URI components, stop here.
3. reassemble the a whole URI from URI components. (c) if you want a 3. reassemble the a whole URI from URI components. (c) if you want a
whole URI stop here. whole URI stop here.
11.2.3. Extension of Syntax 12.2.3. Extension of Syntax
Added the tag range (U+E0000-E0FFF) to the iprivate production. Some Added the tag range (U+E0000-E0FFF) to the iprivate production. Some
IRIs generated with the new syntax may fail to pass very strict IRIs generated with the new syntax may fail to pass very strict
checks relying on the old syntax. But characters in this range checks relying on the old syntax. But characters in this range
should be extremely infrequent anyway. should be extremely infrequent anyway.
11.2.4. More to be added 12.2.4. More to be added
TODO: There are more main changes that need to be documented in this TODO: There are more main changes that need to be documented in this
section. section.
11.3. Change Log 12.3. Change Log
Note to RFC Editor: Please completely remove this section before Note to RFC Editor: Please completely remove this section before
publication. publication.
11.3.1. Changes after draft-ietf-iri-3987bis-01 12.3.1. Changes after draft-ietf-iri-3987bis-01
Changes from draft-ietf-iri-3987bis-01 onwards are available as Changes from draft-ietf-iri-3987bis-01 onwards are available as
changesets in the IETF tools subversion repository at http:// changesets in the IETF tools subversion repository at http://
trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis/ trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis/
draft-ietf-iri-3987bis.xml. draft-ietf-iri-3987bis.xml.
11.3.2. Changes from draft-duerst-iri-bis-07 to 12.3.2. Changes from draft-duerst-iri-bis-07 to
draft-ietf-iri-3987bis-00 draft-ietf-iri-3987bis-00
Changed draft name, date, last paragraph of abstract, and titles in Changed draft name, date, last paragraph of abstract, and titles in
change log, and added this section in moving from change log, and added this section in moving from
draft-duerst-iri-bis-07 (personal submission) to draft-duerst-iri-bis-07 (personal submission) to
draft-ietf-iri-3987bis-00 (WG document). draft-ietf-iri-3987bis-00 (WG document).
11.3.3. Changes from -06 to -07 of draft-duerst-iri-bis 12.3.3. Changes from -06 to -07 of draft-duerst-iri-bis
Major restructuring of the processing model, see Section 11.2. Major restructuring of the processing model, see Section 12.2.
11.4. Changes from -00 to -01 12.4. Changes from -00 to -01
o Removed 'mailto:' before mail addresses of authors. o Removed 'mailto:' before mail addresses of authors.
o Added "<to be done>" as right side of 'href-strip' rule. Fixed o Added "<to be done>" as right side of 'href-strip' rule. Fixed
'|' to '/' for alternatives. '|' to '/' for alternatives.
11.5. Changes from -05 to -06 of draft-duerst-iri-bis-00 12.5. Changes from -05 to -06 of draft-duerst-iri-bis-00
o Add HyperText Reference, change abstract, acks and references for o Add HyperText Reference, change abstract, acks and references for
it it
o Add Masinter back as another editor. o Add Masinter back as another editor.
o Masinter integrates HRef material from HTML5 spec. o Masinter integrates HRef material from HTML5 spec.
o Rewrite introduction sections to modernize. o Rewrite introduction sections to modernize.
11.6. Changes from -04 to -05 of draft-duerst-iri-bis 12.6. Changes from -04 to -05 of draft-duerst-iri-bis
o Updated references. o Updated references.
o Changed IPR text to pre5378Trust200902. o Changed IPR text to pre5378Trust200902.
11.7. Changes from -03 to -04 of draft-duerst-iri-bis 12.7. Changes from -03 to -04 of draft-duerst-iri-bis
o Added explicit abbreviation for LEIRIs. o Added explicit abbreviation for LEIRIs.
o Mentioned LEIRI references. o Mentioned LEIRI references.
o Completed text in LEIRI section about tag characters and about o Completed text in LEIRI section about tag characters and about
specials. specials.
11.8. Changes from -02 to -03 of draft-duerst-iri-bis 12.8. Changes from -02 to -03 of draft-duerst-iri-bis
o Updated some references. o Updated some references.
o Updated Michel Suginard's coordinates. o Updated Michel Suginard's coordinates.
11.9. Changes from -01 to -02 of draft-duerst-iri-bis 12.9. Changes from -01 to -02 of draft-duerst-iri-bis
o Added tag range to iprivate (issue private-include-tags-115). o Added tag range to iprivate (issue private-include-tags-115).
o Added Specials (U+FFF0-FFFD) to Legacy Extended IRIs. o Added Specials (U+FFF0-FFFD) to Legacy Extended IRIs.
11.10. Changes from -00 to -01 of draft-duerst-iri-bis 12.10. Changes from -00 to -01 of draft-duerst-iri-bis
o Changed from "IRIs with Spaces/Controls" to "Legacy Extended IRI" o Changed from "IRIs with Spaces/Controls" to "Legacy Extended IRI"
based on input from the W3C XML Core WG. Moved the relevant based on input from the W3C XML Core WG. Moved the relevant
subsections to the back and promoted them to a section. subsections to the back and promoted them to a section.
o Added some text re. Legacy Extended IRIs to the security section. o Added some text re. Legacy Extended IRIs to the security section.
o Added a IANA Consideration Section. o Added a IANA Consideration Section.
o Added this Change Log Section. o Added this Change Log Section.
o Added a section about "IRIs with Spaces/Controls" (converting from o Added a section about "IRIs with Spaces/Controls" (converting from
a Note in RFC 3987). a Note in RFC 3987).
11.11. Changes from RFC 3987 to -00 of draft-duerst-iri-bis 12.11. Changes from RFC 3987 to -00 of draft-duerst-iri-bis
Fixed errata (see Fixed errata (see
http://www.rfc-editor.org/cgi-bin/errataSearch.pl?rfc=3987). http://www.rfc-editor.org/cgi-bin/errataSearch.pl?rfc=3987).
12. References 13. References
12.1. Normative References 13.1. Normative References
[ASCII] American National Standards Institute, "Coded Character [ASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information Set -- 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986. Interchange", ANSI X3.4, 1986.
[ISO10646] [ISO10646]
International Organization for Standardization, "ISO/IEC International Organization for Standardization, "ISO/IEC
10646:2011: Information Technology - Universal Multiple- 10646:2011: Information Technology - Universal Multiple-
Octet Coded Character Set (UCS)", ISO Standard 10646, Octet Coded Character Set (UCS)", ISO Standard 10646,
March 20011, <http://standards.iso.org/ittf/ March 20011, <http://standards.iso.org/ittf/
skipping to change at page 37, line 23 skipping to change at page 36, line 50
Internationalized Domain Names for Applications (IDNA)", Internationalized Domain Names for Applications (IDNA)",
RFC 5892, August 2010. RFC 5892, August 2010.
[STD63] Yergeau, F., "UTF-8, a transformation format of ISO [STD63] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[STD68] Crocker, D. and P. Overell, "Augmented BNF for Syntax [STD68] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[UNIV6] The Unicode Consortium, "The Unicode Standard, Version [UNIV6] The Unicode Consortium, "The Unicode Standard, Version
6.1.0 (Mountain View, CA, The Unicode Consortium, 2012, 6.2.0 (Mountain View, CA, The Unicode Consortium, 2012,
ISBN 978-1-936213-02-3)", 2012. ISBN 978-1-936213-07-8)", October 2012.
[UTR15] Davis, M. and M. Duerst, "Unicode Normalization Forms", [UTR15] Davis, M. and M. Duerst, "Unicode Normalization Forms",
Unicode Standard Annex #15, March 2008, Unicode Standard Annex #15, March 2008,
<http://www.unicode.org/unicode/reports/tr15/ <http://www.unicode.org/unicode/reports/tr15/
tr15-23.html>. tr15-23.html>.
12.2. Informative References 13.2. Informative References
[Bidi] Duerst, M., Masinter, L., and A. Allawi, "Guidelines for [Bidi] Duerst, M., Masinter, L., and A. Allawi, "Guidelines for
Internationalized Resource Identifiers with Bi-directional Internationalized Resource Identifiers with Bi-directional
Characters (Bidi IRIs)", draft-ietf-iri-bidi-guidelines-02 Characters (Bidi IRIs)", draft-ietf-iri-bidi-guidelines-02
(work in progress), March 2012. (work in progress), March 2012.
[CharMod] Duerst, M., Yergeau, F., Ishida, R., Wolf, M., and T. [CharMod] Duerst, M., Yergeau, F., Ishida, R., Wolf, M., and T.
Texin, "Character Model for the World Wide Web 1.0: Texin, "Character Model for the World Wide Web 1.0:
Resource Identifiers", W3C Candidate Recommendation CR- Resource Identifiers", W3C Candidate Recommendation CR-
charmod-resid-20041122, November 2004, charmod-resid-20041122, November 2004,
<http://www.w3.org/TR/2004/CR-charmod-resid/>. <http://www.w3.org/TR/2004/CR-charmod-resid/>.
[Duerst97] [Duerst97]
Duerst, M., "The Properties and Promises of UTF-8", Proc. Duerst, M., "The Properties and Promises of UTF-8", Proc.
11th International Unicode Conference, San Jose , 11th International Unicode Conference, San Jose ,
September 1997, <http://www.ifi.unizh.ch/mml/mduerst/ September 1997,
papers/PDF/IUC11-UTF-8.pdf>. <http://www.sw.it.aoyama.ac.jp/2012/pub/IUC11-UTF-8.pdf>.
[Equivalence] [Equivalence]
Masinter, L. and M. Duerst, "Equivalence and Masinter, L. and M. Duerst, "Equivalence and
Canonicalization of Internationalized Resource Identifiers Canonicalization of Internationalized Resource Identifiers
(IRIs)", draft-ietf-iri-comparison-01 (work in progress), (IRIs)", draft-ietf-iri-comparison-01 (work in progress),
March 2012. March 2012.
[Gettys] Gettys, J., "URI Model Consequences", [Gettys] Gettys, J., "URI Model Consequences",
<http://www.w3.org/DesignIssues/ModelConsequences>. <http://www.w3.org/DesignIssues/ModelConsequences>.
[HTML4] Raggett, D., Le Hors, A., and I. Jacobs, "HTML 4.01 [HTML4] Raggett, D., Le Hors, A., and I. Jacobs, "HTML 4.01
Specification", W3C Recommendation REC-html401-19991224, Specification", W3C Recommendation REC-html401-19991224,
December 1999, <http://www.w3.org/TR/1999/REC-html401>. December 1999, <http://www.w3.org/TR/1999/REC-html401>.
[RFC2130] Weider, C., Preston, C., Simonsen, K., Alvestrand, H., [HTMLURL] van Kesteren, A., "URL", October 2012,
Atkinson, R., Crispin, M., and P. Svanberg, "The Report of <http://url.spec.whatwg.org/>.
the IAB Character Set Workshop held 29 February - 1 March,
1996", RFC 2130, April 1997.
[RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.
[RFC2192] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997. [RFC2192] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997.
[RFC2277] Alvestrand, H., "IETF Policy on Character Sets and [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998. Languages", BCP 18, RFC 2277, January 1998.
[RFC2384] Gellens, R., "POP URL Scheme", RFC 2384, August 1998. [RFC2384] Gellens, R., "POP URL Scheme", RFC 2384, August 1998.
skipping to change at page 39, line 15 skipping to change at page 38, line 40
Extensible Messaging and Presence Protocol (XMPP)", Extensible Messaging and Presence Protocol (XMPP)",
RFC 5122, February 2008. RFC 5122, February 2008.
[RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
Encodings for Internationalized Domain Names", RFC 6055, Encodings for Internationalized Domain Names", RFC 6055,
February 2011. February 2011.
[RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto' [RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
URI Scheme", RFC 6068, October 2010. URI Scheme", RFC 6068, October 2010.
[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
September 2011.
[UNIXML] Duerst, M. and A. Freytag, "Unicode in XML and other [UNIXML] Duerst, M. and A. Freytag, "Unicode in XML and other
Markup Languages", Unicode Technical Report #20, World Markup Languages", Unicode Technical Report #20, World
Wide Web Consortium Note, June 2003, Wide Web Consortium Note, June 2003,
<http://www.w3.org/TR/unicode-xml/>. <http://www.w3.org/TR/unicode-xml/>.
[UTR36] Davis, M. and M. Suignard, "Unicode Security [UTR36] Davis, M. and M. Suignard, "Unicode Security
Considerations", Unicode Technical Report #36, Considerations", Unicode Technical Report #36,
August 2010, <http://unicode.org/reports/tr36/>. August 2010, <http://unicode.org/reports/tr36/>.
[XLink] DeRose, S., Maler, E., Orchard, D., and N. Walsh, "XML [XLink] DeRose, S., Maler, E., Orchard, D., and N. Walsh, "XML
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