source: draft-ietf-iri-3987bis/draft-ietf-iri-3987bis.xml @ 114

Last change on this file since 114 was 114, checked in by duerst@…, 7 years ago

added Adil's name in Arabic script

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1<?xml version="1.0"?>
2<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
3<!ENTITY rfc2119 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
4<!ENTITY rfc2130 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2130.xml">
5<!ENTITY rfc2141 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2141.xml">
6<!ENTITY rfc2192 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2192.xml">
7<!ENTITY rfc2277 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2277.xml">
8<!ENTITY rfc2384 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2384.xml">
9<!ENTITY rfc2396 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2396.xml">
10<!ENTITY rfc2397 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2397.xml">
11<!ENTITY rfc2616 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2616.xml">
12<!ENTITY rfc2640 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2640.xml">
13<!ENTITY rfc3491 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3491.xml">
14<!ENTITY rfc3986 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3986.xml">
15<!ENTITY rfc5122 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5122.xml">
16<!ENTITY rfc5890 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5890.xml">
17<!ENTITY rfc5891 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5891.xml">
18<!ENTITY rfc6055 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.6055.xml">
19]>
20<?rfc strict='yes'?>
21
22<?xml-stylesheet type='text/css' href='rfc2629.css' ?>
23<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
24<?rfc symrefs='yes'?>
25<?rfc sortrefs='yes'?>
26<?rfc iprnotified="no" ?>
27<?rfc toc='yes'?>
28<?rfc compact='yes'?>
29<?rfc subcompact='no'?>
30<rfc ipr="pre5378Trust200902" docName="draft-ietf-iri-3987bis-11" category="std" xml:lang="en" obsoletes="3987">
31<front>
32<title abbrev="IRIs">Internationalized Resource Identifiers (IRIs)</title>
33
34<author initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst   (Note: Please write &quot;Duerst&quot; with u-umlaut wherever possible, for example as &quot;D&amp;#252;rst&quot; in XML and HTML.)">
35    <organization>Aoyama Gakuin University<ionly> (青山学院大学)</ionly> </organization>
36    <address>
37  <postal>
38  <street>5-10-1 Fuchinobe</street>
39  <street>Chuo-ku</street>
40  <city>Sagamihara</city>
41  <region>Kanagawa</region>
42  <code>252-5258</code>
43  <country>Japan</country>
44  </postal>
45  <phone>+81 42 759 6329</phone>
46  <facsimile>+81 42 759 6495</facsimile>
47  <email>duerst@it.aoyama.ac.jp</email>
48  <uri><aonly>http://www.sw.it.aoyama.ac.jp/D%C3%BCrst/ (Note: This is the percent-encoded form of an IRI)</aonly><ionly>http://www.sw.it.aoyama.ac.jp/Dürst/</ionly></uri>
49  </address>
50</author>
51 
52  <author initials="M.L." surname="Suignard" fullname="Michel Suignard">
53   <organization>Unicode Consortium</organization>
54   <address>
55   <postal>
56   <street></street>
57   <street>P.O. Box 391476</street>
58   <city>Mountain View</city>
59   <region>CA</region>
60   <code>94039-1476</code>
61   <country>U.S.A.</country>
62   </postal>
63   <phone>+1-650-693-3921</phone>
64   <email>michel@unicode.org</email>
65   <uri>http://www.suignard.com</uri>
66   </address>
67</author>
68<author initials="L." surname="Masinter" fullname="Larry Masinter">
69   <organization>Adobe</organization>
70   <address>
71   <postal>
72   <street>345 Park Ave</street>
73   <city>San Jose</city>
74   <region>CA</region>
75   <code>95110</code>
76   <country>U.S.A.</country>
77   </postal>
78   <phone>+1-408-536-3024</phone>
79   <email>masinter@adobe.com</email>
80   <uri>http://larry.masinter.net</uri>
81   </address>
82</author>
83
84<date year="2012" />
85<area>Applications</area>
86<workgroup>Internationalized Resource Identifiers (iri)</workgroup>
87<keyword>IRI</keyword>
88<keyword>Internationalized Resource Identifier</keyword>
89<keyword>UTF-8</keyword>
90<keyword>URI</keyword>
91<keyword>IDN</keyword>
92<keyword>LEIRI</keyword>
93
94<abstract>
95<t>This document defines the Internationalized Resource Identifier
96(IRI) protocol element, as an extension of the Uniform Resource
97Identifier (URI).  An IRI is a sequence of characters from the
98Universal Character Set (Unicode/ISO 10646). Grammar and processing
99rules are given for IRIs and related syntactic forms.</t>
100
101<t>Defining IRI as a new protocol element (rather than updating or
102extending the definition of URI) allows independent orderly
103transitions: protocols and languages that use URIs must
104explicitly choose to allow IRIs.</t>
105
106<t>Guidelines are provided for the use and deployment of IRIs and
107related protocol elements when revising protocols, formats, and
108software components that currently deal only with URIs.</t>
109
110<t>This document is part of a set of documents intended to
111replace RFC 3987.</t>
112
113</abstract>
114  <note title='RFC Editor: Please remove the next paragraph before publication.'>
115    <t>This (and several companion documents) are intended to obsolete RFC 3987,
116    and also move towards IETF Draft Standard.  For discussion and comments on these
117    drafts, please join the IETF IRI WG by subscribing to the mailing
118    list public-iri@w3.org, archives at http://lists.w3.org/archives/public/public-iri/.
119    For a list of open issues, please see
120    the issue tracker of the WG at http://trac.tools.ietf.org/wg/iri/trac/report/1.
121    For a list of individual edits, please see the change history at
122    http://trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis.</t>
123</note>
124</front>
125<middle>
126
127<section title="Introduction">
128
129<section title="Overview and Motivation" anchor="overview">
130
131<t>A Uniform Resource Identifier (URI) is defined in <xref
132target="RFC3986"/> as a sequence of characters chosen from a limited
133subset of the repertoire of US-ASCII <xref target="ASCII"/>
134characters.</t>
135
136<t>The characters in URIs are frequently used for representing words
137of natural languages.  This usage has many advantages: Such URIs are
138easier to memorize, easier to interpret, easier to transcribe, easier
139to create, and easier to guess. For most languages other than English,
140however, the natural script uses characters other than A - Z. For many
141people, handling Latin characters is as difficult as handling the
142characters of other scripts is for those who use only the Latin
143script. Many languages with non-Latin scripts are transcribed with
144Latin letters. These transcriptions are now often used in URIs, but
145they introduce additional difficulties.</t>
146
147<t>The infrastructure for the appropriate handling of characters from
148additional scripts is now widely deployed in operating system and
149application software. Software that can handle a wide variety of
150scripts and languages at the same time is increasingly common. Also,
151an increasing number of protocols and formats can carry a wide range of
152characters.</t>
153
154<t>URIs are composed out of a very limited repertoire of characters;
155this design choice was made to support global transcription (see <xref
156target="RFC3986"/> section 1.2.1.).  Reliable transition between a URI
157(as an abstract protocol element composed of a sequence of characters)
158and a presentation of that URI (written on a napkin, read out loud)
159and back is relatively straightforward, because of the limited
160repertoire of characters used.  IRIs are designed to satisfy a
161different set of use requirements; in particular, to allow IRIs to be
162written in ways that are more meaningful to their users, even at the
163expense of global transcribability. However, ensuring reliability of
164the transition between an IRI and its presentation and back is more
165difficult and complex when dealing with the larger set of Unicode
166characters.  For example, Unicode supports multiple ways of encoding
167complex combinations of characters and accents, with multiple
168character sequences that can result in the same presentation.</t>
169
170<t>This document defines the protocol element called Internationalized
171Resource Identifier (IRI), which allows applications of URIs to be
172extended to use resource identifiers that have a much wider repertoire
173of characters. It also provides corresponding "internationalized"
174versions of other constructs from <xref target="RFC3986"/>, such as
175URI references. The syntax of IRIs is defined in <xref
176target="syntax"/>.
177</t>
178
179<t>Within this document,
180               <xref target="IRIuse"/> discusses the use
181of IRIs in different situations.  <xref target="guidelines"/> gives
182additional informative guidelines.  <xref target="security"/>
183discusses IRI-specific security considerations.</t>
184
185<t>This specification is part of a collection of specifications
186intended to replace <xref target="RFC3987"/>.
187<xref target="Bidi"/> discusses the special case of
188bidirectional IRIs, IRIs using characters from scripts written
189right-to-left.
190<xref target="Equivalence"/> gives guidelines for applications wishing
191to determine if two IRIs are equivalent, as well as defining
192some equivalence methods.
193<xref target="RFC4395bis"/> updates the URI scheme registration
194guidelines and procedures to note that every URI scheme is also
195automatically an IRI scheme and to allow scheme definitions
196to be directly described in terms of Unicode characters.
197</t>
198
199</section> <!-- overview -->
200
201<section title="Applicability" anchor="Applicability">
202
203<t>IRIs are designed to allow protocols and software that deal with
204URIs to be updated to handle IRIs. Processing of
205IRIs is accomplished by extending the URI syntax while retaining (and
206not expanding) the set of "reserved" characters, such that the syntax
207for any URI scheme may be extended to allow non-ASCII
208characters. In addition, following parsing of an IRI, it is possible
209to construct a corresponding URI by first encoding characters outside
210of the allowed URI range and then reassembling the components.
211</t>
212
213<t>Practical use of IRIs forms in place of URIs forms depends on the
214following conditions being met:</t>
215
216<t><list style="hanging">
217   
218<t hangText="a.">A protocol or format element MUST be explicitly designated to be
219  able to carry IRIs. The intent is to avoid introducing IRIs into
220  contexts that are not defined to accept them.  For example, XML
221  schema <xref target="XMLSchema"/> has an explicit type "anyURI" that
222  includes IRIs and IRI references. Therefore, IRIs and IRI references
223  can be used in attributes and elements of type "anyURI".  On the other
224  hand, in HTTP/1.1 (<xref target="RFC2616"/>) , the
225  Request URI is defined as a URI, which means that direct use of IRIs
226  is not allowed in HTTP requests.</t>
227
228<t hangText="b.">The protocol or format carrying the IRIs MUST have a
229  mechanism to represent the wide range of characters used in IRIs,
230  either natively or by some protocol- or format-specific escaping
231  mechanism (for example, numeric character references in <xref
232  target="XML1"/>).</t>
233
234<t hangText="c.">The URI scheme definition, if it explicitly allows a
235  percent sign ("%") in any syntactic component, SHOULD define the
236  interpretation of sequences of percent-encoded octets (using "%XX"
237  hex octets) as octets from sequences of UTF-8 encoded characters; this
238  is recommended in the guidelines for registering new schemes, <xref
239  target="RFC4395bis"/>.  For example, this is the practice for IMAP URLs
240  <xref target="RFC2192"/>, POP URLs <xref target="RFC2384"/> and the
241  URN syntax <xref target="RFC2141"/>). Note that use of
242  percent-encoding may also be restricted in some situations, for
243  example, URI schemes that disallow percent-encoding might still be
244  used with a fragment identifier which is percent-encoded (e.g.,
245  <xref target="XPointer"/>). See <xref target="UTF8use"/> for further
246  discussion.</t>
247</list></t>
248
249</section> <!-- applicability -->
250
251<section title="Definitions" anchor="sec-Definitions">
252 
253<t>The following definitions are used in this document; they follow the
254terms in <xref target="RFC2130"/>, <xref target="RFC2277"/>, and
255<xref target="ISO10646"/>.</t>
256<t><list style="hanging">
257   
258<t hangText="character:">A member of a set of elements used for the
259    organization, control, or representation of data. For example,
260    "LATIN CAPITAL LETTER A" names a character.</t>
261   
262<t hangText="octet:">An ordered sequence of eight bits considered as a
263    unit.</t>
264   
265<t hangText="character repertoire:">A set of characters (set in the
266    mathematical sense).</t>
267   
268<t hangText="sequence of characters:">A sequence of characters (one
269    after another).</t>
270   
271<t hangText="sequence of octets:">A sequence of octets (one after
272    another).</t>
273   
274<t hangText="character encoding:">A method of representing a sequence
275    of characters as a sequence of octets (maybe with variants). Also,
276    a method of (unambiguously) converting a sequence of octets into a
277    sequence of characters.</t>
278   
279<t hangText="charset:">The name of a parameter or attribute used to
280    identify a character encoding.</t>
281   
282<t hangText="UCS:">Universal Character Set. The coded character set
283    defined by ISO/IEC 10646 <xref target="ISO10646"/> and the Unicode
284    Standard <xref target="UNIV6"/>.</t>
285   
286<t hangText="IRI reference:">Denotes the common usage of an
287    Internationalized Resource Identifier. An IRI reference may be
288    absolute or relative.  However, the "IRI" that results from such a
289    reference only includes absolute IRIs; any relative IRI references
290    are resolved to their absolute form.  Note that in <xref
291    target="RFC2396"/> URIs did not include fragment identifiers, but
292    in <xref target="RFC3986"/> fragment identifiers are part of
293    URIs.</t>
294   
295<t hangText="LEIRI (Legacy Extended IRI):">  This term is used in
296   various XML specifications to refer
297   to strings that, although not valid IRIs, are acceptable input to
298   the processing rules in <xref target="LEIRIspec" />.</t>
299
300<t hangText="running text:">Human text (paragraphs, sentences,
301   phrases) with syntax according to orthographic conventions of a
302   natural language, as opposed to syntax defined for ease of
303   processing by machines (e.g., markup, programming languages).</t>
304   
305<t hangText="protocol element:">Any portion of a message that affects
306    processing of that message by the protocol in question.</t>
307   
308<t hangText="create (a URI or IRI):">With respect to URIs and IRIs,
309     the term is used for the initial creation. This may be the
310     initial creation of a resource with a certain identifier, or the
311     initial exposition of a resource under a particular
312     identifier.</t>
313   
314<t hangText="generate (a URI or IRI):">With respect to URIs and IRIs,
315     the term is used when the identifier is generated by derivation
316     from other information.</t>
317
318<t hangText="parsed URI component:">When a URI processor parses a URI
319   (following the generic syntax or a scheme-specific syntax, the result
320   is a set of parsed URI components, each of which has a type
321   (corresponding to the syntactic definition) and a sequence of URI
322   characters.  </t>
323
324<t hangText="parsed IRI component:">When an IRI processor parses
325   an IRI directly, following the general syntax or a scheme-specific
326   syntax, the result is a set of parsed IRI components, each of
327   which has a type (corresponding to the syntactic definition)
328   and a sequence of IRI characters. (This definition is analogous
329   to "parsed URI component".)</t>
330
331<t hangText="IRI scheme:">A URI scheme may also be known as
332   an "IRI scheme" if the scheme's syntax has been extended to
333   allow non-US-ASCII characters according to the rules in this
334   document.</t>
335
336</list></t>
337</section> <!-- definitions -->
338<section title="Notation" anchor="sec-Notation">
339     
340<t>RFCs and Internet Drafts currently do not allow any characters
341outside the US-ASCII repertoire. Therefore, this document uses various
342special notations for such characters in examples.</t>
343     
344<t>In text, characters outside US-ASCII are sometimes referenced by
345using a prefix of 'U+', followed by four to six hexadecimal
346digits.</t>
347
348<t>To represent characters outside US-ASCII in examples, this document
349uses 'XML Notation'.</t>
350
351<t>XML Notation uses a leading '&amp;#x', a trailing ';', and the
352hexadecimal number of the character in the UCS in between. For
353example, &amp;#x42F; stands for CYRILLIC CAPITAL LETTER YA. In this
354notation, an actual '&amp;' is denoted by '&amp;amp;'.</t>
355
356<t>To denote actual octets in examples (as opposed to percent-encoded
357octets), the two hex digits denoting the octet are enclosed in "&lt;"
358and "&gt;".  For example, the octet often denoted as 0xc9 is denoted
359here as &lt;c9&gt;.</t>
360
361<t> In this document, the key words "MUST", "MUST NOT", "REQUIRED",
362"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
363and "OPTIONAL" are to be interpreted as described in <xref
364target="RFC2119"/>.</t>
365
366</section> <!-- notation -->
367</section> <!-- introduction -->
368
369<section title="IRI Syntax" anchor="syntax">
370<t>This section defines the syntax of Internationalized Resource
371Identifiers (IRIs).</t>
372
373<t>As with URIs, an IRI is defined as a sequence of characters, not as
374a sequence of octets.
375This definition accommodates the fact that IRIs
376may be written on paper or read over the radio as well as stored or
377transmitted digitally.  The same IRI might be represented as different
378sequences of octets in different protocols or documents if these
379protocols or documents use different character encodings (and/or
380transfer encodings).  Using the same character encoding as the
381containing protocol or document ensures that the characters in the IRI
382can be handled (e.g., searched, converted, displayed) in the same way
383as the rest of the protocol or document.</t>
384
385<section title="Summary of IRI Syntax" anchor="summary">
386
387<t>The IRI syntax extends the URI syntax in <xref
388target="RFC3986"/> by extending the class of unreserved characters,
389primarily by adding the characters of the UCS (Universal Character Set, <xref
390target="ISO10646"/>) beyond U+007F, subject to the limitations given
391in the syntax rules below and in <xref target="limitations"/>.</t>
392
393<t>The syntax and use of components and reserved characters is the
394same as that in <xref target="RFC3986"/>. Each URI scheme thus also
395functions as an IRI scheme, in that scheme-specific parsing rules
396for URIs of a scheme are extended to allow parsing of IRIs using
397the same parsing rules.</t>
398
399<t>All the operations defined in <xref target="RFC3986"/>, such as the
400resolution of relative references, can be applied to IRIs by
401IRI-processing software in exactly the same way as they are for URIs
402by URI-processing software.</t>
403
404<t>Characters outside the US-ASCII repertoire MUST NOT be reserved and
405therefore MUST NOT be used for syntactical purposes, such as to
406delimit components in newly defined schemes. For example, U+00A2, CENT
407SIGN, is not allowed as a delimiter in IRIs, because it is in the
408'iunreserved' category. This is similar to the fact that it is not
409possible to use '-' as a delimiter in URIs, because it is in the
410'unreserved' category.</t>
411
412</section> <!-- summary -->
413<section title="ABNF for IRI References and IRIs" anchor="abnf">
414
415<t>An ABNF definition for IRI references (which are the most general
416concept and the start of the grammar) and IRIs is given here. The
417syntax of this ABNF is described in <xref target="STD68"/>. Character
418numbers are taken from the UCS, without implying any actual binary
419encoding. Terminals in the ABNF are characters, not octets.</t>
420
421<t>The following grammar closely follows the URI grammar in <xref
422target="RFC3986"/>, except that the range of unreserved characters is
423expanded to include UCS characters, with the restriction that private
424UCS characters can occur only in query parts. The grammar is split
425into two parts: Rules that differ from <xref target="RFC3986"/>
426because of the above-mentioned expansion, and rules that are the same
427as those in <xref target="RFC3986"/>. For rules that are different
428than those in <xref target="RFC3986"/>, the names of the non-terminals
429have been changed as follows. If the non-terminal contains 'URI', this
430has been changed to 'IRI'. Otherwise, an 'i' has been prefixed.
431The rule &lt;pct-form> has been introduced in order to be able to reference it from other parts of
432the document.</t>
433
434<!--
435for line length measuring in artwork (max 72 chars, three chars at start):
436      1         2         3         4         5         6         7
437456789012345678901234567890123456789012345678901234567890123456789012
438-->
439<figure>
440<preamble>The following rules are different from those in <xref target="RFC3986"/>:</preamble>
441<artwork>
442IRI            = scheme ":" ihier-part [ "?" iquery ]
443                 [ "#" ifragment ]
444
445ihier-part     = "//" iauthority ipath-abempty
446               / ipath-absolute
447               / ipath-rootless
448               / ipath-empty
449
450IRI-reference  = IRI / irelative-ref
451
452absolute-IRI   = scheme ":" ihier-part [ "?" iquery ]
453
454irelative-ref  = irelative-part [ "?" iquery ] [ "#" ifragment ]
455
456irelative-part = "//" iauthority ipath-abempty
457               / ipath-absolute
458               / ipath-noscheme
459               / ipath-empty
460
461iauthority     = [ iuserinfo "@" ] ihost [ ":" port ]
462iuserinfo      = *( iunreserved / pct-form / sub-delims / ":" )
463ihost          = IP-literal / IPv4address / ireg-name
464
465pct-form       = pct-encoded
466
467ireg-name      = *( iunreserved / sub-delims )
468
469ipath          = ipath-abempty   ; begins with "/" or is empty
470               / ipath-absolute  ; begins with "/" but not "//"
471               / ipath-noscheme  ; begins with a non-colon segment
472               / ipath-rootless  ; begins with a segment
473               / ipath-empty     ; zero characters
474
475ipath-abempty  = *( path-sep isegment )
476ipath-absolute = path-sep [ isegment-nz *( path-sep isegment ) ]
477ipath-noscheme = isegment-nz-nc *( path-sep isegment )
478ipath-rootless = isegment-nz *( path-sep isegment )
479ipath-empty    = ""
480path-sep       = "/"
481
482isegment       = *ipchar
483isegment-nz    = 1*ipchar
484isegment-nz-nc = 1*( iunreserved / pct-form / sub-delims
485                     / "@" )
486               ; non-zero-length segment without any colon ":"
487
488ipchar         = iunreserved / pct-form / sub-delims / ":"
489               / "@"
490 
491iquery         = *( ipchar / iprivate / "/" / "?" )
492
493ifragment      = *( ipchar / "/" / "?" )
494
495iunreserved    = ALPHA / DIGIT / "-" / "." / "_" / "~" / ucschar
496
497ucschar        = %xA0-D7FF / %xF900-FDCF / %xFDF0-FFEF
498               / %x10000-1FFFD / %x20000-2FFFD / %x30000-3FFFD
499               / %x40000-4FFFD / %x50000-5FFFD / %x60000-6FFFD
500               / %x70000-7FFFD / %x80000-8FFFD / %x90000-9FFFD
501               / %xA0000-AFFFD / %xB0000-BFFFD / %xC0000-CFFFD
502               / %xD0000-DFFFD / %xE1000-EFFFD
503
504iprivate       = %xE000-F8FF / %xE0000-E0FFF / %xF0000-FFFFD
505               / %x100000-10FFFD
506</artwork>
507</figure>
508
509<t>Some productions are ambiguous. The "first-match-wins" (a.k.a. "greedy")
510algorithm applies. For details, see <xref target="RFC3986"/>.</t>
511
512<figure>
513<preamble>The following rules are the same as those in <xref target="RFC3986"/>:</preamble>
514<artwork>
515scheme         = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
516 
517port           = *DIGIT
518 
519IP-literal     = "[" ( IPv6address / IPvFuture  ) "]"
520 
521IPvFuture      = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )
522 
523IPv6address    =                            6( h16 ":" ) ls32
524               /                       "::" 5( h16 ":" ) ls32
525               / [               h16 ] "::" 4( h16 ":" ) ls32
526               / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
527               / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
528               / [ *3( h16 ":" ) h16 ] "::"    h16 ":"   ls32
529               / [ *4( h16 ":" ) h16 ] "::"              ls32
530               / [ *5( h16 ":" ) h16 ] "::"              h16
531               / [ *6( h16 ":" ) h16 ] "::"
532               
533h16            = 1*4HEXDIG
534ls32           = ( h16 ":" h16 ) / IPv4address
535
536IPv4address    = dec-octet "." dec-octet "." dec-octet "." dec-octet
537
538dec-octet      = DIGIT                 ; 0-9
539               / %x31-39 DIGIT         ; 10-99
540               / "1" 2DIGIT            ; 100-199
541               / "2" %x30-34 DIGIT     ; 200-249
542               / "25" %x30-35          ; 250-255
543           
544pct-encoded    = "%" HEXDIG HEXDIG
545
546unreserved     = ALPHA / DIGIT / "-" / "." / "_" / "~"
547reserved       = gen-delims / sub-delims
548gen-delims     = ":" / "/" / "?" / "#" / "[" / "]" / "@"
549sub-delims     = "!" / "$" / "&amp;" / "'" / "(" / ")"
550               / "*" / "+" / "," / ";" / "="
551</artwork></figure>
552
553<t>This syntax does not support IPv6 scoped addressing zone identifiers.</t>
554
555</section> <!-- abnf -->
556
557</section> <!-- syntax -->
558
559<section title="Processing IRIs and related protocol elements" anchor="processing">
560
561<t>IRIs are meant to replace URIs in identifying resources within new
562versions of protocols, formats, and software components that use a
563UCS-based character repertoire.  Protocols and components may use and
564process IRIs directly. However, there are still numerous systems and
565protocols which only accept URIs or components of parsed URIs; that is,
566they only accept sequences of characters within the subset of US-ASCII
567characters allowed in URIs. </t>
568
569<t>This section defines specific processing steps for IRI consumers
570which establish the relationship between the string given and the
571interpreted derivatives. These
572processing steps apply to both IRIs and IRI references (i.e., absolute
573or relative forms); for IRIs, some steps are scheme specific. </t>
574
575<section title="Converting to UCS" anchor="ucsconv"> 
576 
577<t>Input that is already in a Unicode form (i.e., a sequence of Unicode
578 characters or an octet-stream representing a Unicode-based character
579 encoding such as UTF-8 or UTF-16) should be left as is and not
580 normalized or changed.</t>
581
582  <t>An IRI or IRI reference is a sequence of characters from the UCS.
583    For input from presentations (written on paper, read aloud)
584    or translation from other representations (a text stream using a legacy character
585    encoding), convert the input to Unicode.
586    Note that some character encodings or transcriptions can be converted
587    to or represented by more than one sequence of Unicode characters.
588
589    Ideally the resulting IRI would use a normalized form,
590    such as Unicode Normalization Form C <xref target="UTR15"/>,
591    since that ensures a stable, consistent representation
592    that is most likely to produce the intended results.
593    Previous versions of this specification required
594    normalization at this step. However, attempts to
595    require normalization in other protocols have met with
596    strong enough resistance that requiring normalization
597    here was considered impractical.
598    Implementers and users are cautioned that, while denormalized character sequences are valid,
599    they might be difficult for other users or processes to reproduce
600    and might lead to unexpected results.
601  <!-- raise on list:
602    It is recommended
603    that the processing of IRI components treat
604    strings with the same normalized forms as equivalent.
605   -->
606  </t>
607
608</section> <!-- ucsconv -->
609
610<section title="Parse the IRI into IRI components">
611
612<t>Parse the IRI, either as a relative reference (no scheme)
613or using scheme specific processing (according to the scheme
614given); the result is a set of parsed IRI components.</t>
615
616</section> <!-- parse -->
617
618<section title="General percent-encoding of IRI components" anchor="compmapping">
619   
620<t>Except as noted in the following subsections, IRI components are mapped
621to the equivalent URI components by percent-encoding those characters
622not allowed in URIs. Previous processing steps will have removed
623some characters, and the interpretation of reserved characters will
624have already been done (with the syntactic reserved characters outside
625of the IRI component). This mapping is defined for all sequences
626of Unicode characters, whether or not they are valid for the component
627in question. </t>
628   
629<t>For each character which is not allowed anywhere in a valid URI
630 apply the following steps. </t>
631<t><list style="hanging">
632
633<t hangText="Convert to UTF-8:">Convert the character to a sequence of
634  one or more octets using UTF-8 <xref target="STD63"/>.</t>
635
636<t hangText="Percent encode:">Convert each octet of this sequence to %HH,
637   where HH is the hexadecimal notation of the octet value. The
638   hexadecimal notation SHOULD use uppercase letters. (This is the
639   general URI percent-encoding mechanism in Section 2.1 of <xref
640   target="RFC3986"/>.)</t>
641   
642</list></t>
643
644<t>Note that the mapping is an identity transformation for parsed URI
645components of valid URIs, and is idempotent: applying the mapping a
646second time will not change anything.</t>
647</section> <!-- general conversion -->
648
649<section title="Mapping ireg-name" anchor="dnsmapping">
650  <t>The mapping from &lt;ireg-name> to a &lt;reg-name> requires a choice
651    between one of the two methods described below.</t>
652  <section title='Mapping using Percent-Encoding' anchor='dnspercent'>
653  <t>The ireg-name component SHOULD be converted
654    according to the general procedure for percent-encoding
655    of IRI components described in <xref target="compmapping"/>.</t>
656 
657  <t>For example, the IRI
658    <vspace/>"http://r&amp;#xE9;sum&amp;#xE9;.example.org"<vspace/> will be
659    converted to <vspace/>"http://r%C3%A9sum%C3%A9.example.org".</t>
660
661  <t>This conversion for ireg-name is in line with Section 3.2.2
662    of <xref target="RFC3986"/>, which does not mandate
663    a particular registered name lookup technology. For further background,
664    see <xref target="RFC6055"/> and <xref target="Gettys"/>.</t>
665</section> <!-- dnspercent -->
666<section title="Mapping using Punycode" anchor='dnspunycode'>
667  <t>In situations where it is certain that &lt;ireg-name> is intended
668    to be used as a domain name to be processed by Domain Name Lookup
669    (as per <xref target="RFC5891"/>), an alternative method MAY be
670    used, converting &lt;ireg-name> as follows:</t>
671
672  <t>If there are any sequences of &lt;pct-encoded&gt;, and their
673    corresponding octets all represent valid UTF-8
674    octet sequences, then convert these back to Unicode
675    character sequences. (If any &lt;pct-encoded&gt; sequences are not
676    valid UTF-8 octet sequences, then leave the entire field as is
677    without any change, since punycode encoding would not succeed.)</t>
678
679<t>Replace the ireg-name part of the IRI by the part converted using
680the Domain Name Lookup procedure (Subsections 5.3 to 5.5) of <xref target="RFC5891"/>.
681  on each dot-separated label, and by using U+002E
682(FULL STOP) as a label separator.
683This procedure may fail, but this would mean that the IRI cannot be resolved.
684In such cases, if the domain name conversion fails, then the
685entire IRI conversion fails. Processors that have no mechanism for
686signalling a failure MAY instead substitute an otherwise
687invalid host name, although such processing SHOULD be avoided.</t>
688
689<t>For example, the IRI
690<vspace/>"http://r&amp;#xE9;sum&amp;#xE9;.example.org"<vspace/> is
691converted to <vspace/>"http://xn--rsum-bad.example.org".</t>
692  <t>This conversion for ireg-name will be better able to deal with legacy
693    infrastructure that cannot handle percent-encoding in domain names.</t>
694</section> <!-- punicode -->
695  <section title="Additional Considerations">
696
697<t><list style="hanging"> 
698<t hangText="Note:">Domain Names may appear in parts of an IRI other
699than the ireg-name part.  It is the responsibility of scheme-specific
700implementations (if the Internationalized Domain Name is part of the
701scheme syntax) or of server-side implementations (if the
702Internationalized Domain Name is part of 'iquery') to apply the
703necessary conversions at the appropriate point. Example: Trying to
704validate the Web page at<vspace/>
705http://r&amp;#xE9;sum&amp;#xE9;.example.org would lead to an IRI of
706<vspace/>http://validator.w3.org/check?uri=http%3A%2F%2Fr&amp;#xE9;sum&amp;#xE9;.<vspace/>example.org,
707which would convert to a URI
708of<vspace/>http://validator.w3.org/check?uri=http%3A%2F%2Fr%C3%A9sum%C3%A9.<vspace/>example.org.
709The server-side implementation is responsible for making the
710necessary conversions to be able to retrieve the Web page.</t>
711
712<t hangText="Note:">In this process, characters allowed in URI
713references and existing percent-encoded sequences are not encoded further.
714(This mapping is similar to, but different from, the encoding applied
715when arbitrary content is included in some part of a URI.)
716
717For example, an IRI of
718<vspace/>"http://www.example.org/red%09ros&amp;#xE9;#red"
719(in XML notation) is converted to
720<vspace/>"http://www.example.org/red%09ros%C3%A9#red", not to
721something like
722<vspace/>"http%3A%2F%2Fwww.example.org%2Fred%2509ros%C3%A9%23red".</t>
723
724</list></t>
725</section> <!-- additional -->
726</section> <!-- dnsmapping -->
727
728<section title="Mapping query components" anchor="querymapping">
729
730<t>For compatibility with existing deployed HTTP infrastructure,
731the following special case applies for schemes "http" and "https"
732and IRIs whose origin has a document charset other than one which
733is UCS-based (e.g., UTF-8 or UTF-16). In such a case, the "query"
734component of an IRI is mapped into a URI by using the document
735charset rather than UTF-8 as the binary representation before
736pct-encoding. This mapping is not applied for any other scheme
737or component.</t>
738
739</section> <!-- querymapping -->
740
741<section title="Mapping IRIs to URIs" anchor="mapping">
742
743<t>The mapping from an IRI to URI is accomplished by applying the
744mapping above (from IRI to URI components) and then reassembling a URI
745from the parsed URI components using the original punctuation that
746delimited the IRI components. </t>
747
748</section> <!-- mapping -->
749</section> <!-- processing -->
750
751<section title="Converting URIs to IRIs" anchor="URItoIRI">
752
753  <t>In some situations, for presentation and further processing,
754it is desirable to convert a URI into an equivalent IRI
755without unnecessary percent encoding.
756Of course, every URI is already an IRI in its own right without any
757conversion. This section gives one possible procedure for URI to IRI mapping.</t>
758
759<t>
760The conversion described in this section, if given a valid URI, will
761result in an IRI that maps back to the URI used as an input for the
762conversion (except for potential case differences in percent-encoding
763and for potential percent-encoded unreserved characters).
764
765However, the IRI resulting from this conversion may differ
766from the original IRI (if there ever was one).</t> 
767
768<t>URI-to-IRI conversion removes percent-encodings, but not all
769percent-encodings can be eliminated. There are several reasons for
770this:</t>
771
772<t><list style="hanging">
773
774<t hangText="1.">Some percent-encodings are necessary to distinguish
775    percent-encoded and unencoded uses of reserved characters.</t>
776
777<t hangText="2.">Some percent-encodings cannot be interpreted as sequences
778    of UTF-8 octets.<vspace blankLines="1"/>
779    (Note: The octet patterns of UTF-8 are highly regular.
780    Therefore, there is a very high probability, but no guarantee,
781    that percent-encodings that can be interpreted as sequences of UTF-8
782    octets actually originated from UTF-8. For a detailed discussion,
783    see <xref target="Duerst97"/>.)</t>
784
785<t hangText="3.">The conversion may result in a character that is not
786    appropriate in an IRI. See <xref target="abnf"/>,
787      and <xref target="limitations"/> for further details.</t>
788
789<t hangText="4.">IRI to URI conversion has different rules for
790    dealing with domain names and query parameters.</t>
791
792</list></t>
793
794<t>Conversion from a URI to an IRI MAY be done by using the following
795steps:
796
797<list style="hanging">
798<t hangText="1.">Represent the URI as a sequence of octets in
799       US-ASCII.</t>
800
801<t hangText="2.">Convert all percent-encodings ("%" followed by two
802      hexadecimal digits) to the corresponding octets, except those
803      corresponding to "%", characters in "reserved", and characters
804      in US-ASCII not allowed in URIs.</t> 
805
806<t hangText="3.">Re-percent-encode any octet produced in step 2 that
807      is not part of a strictly legal UTF-8 octet sequence.</t>
808
809
810<t hangText="4.">Re-percent-encode all octets produced in step 3 that
811      in UTF-8 represent characters that are not appropriate according
812      to <xref target="abnf"/>  and <xref
813      target="limitations"/>.</t> 
814
815<t hangText="5.">Interpret the resulting octet sequence as a sequence
816      of characters encoded in UTF-8.</t>
817
818<t hangText="6.">URIs known to contain domain names in the reg-name
819      component SHOULD convert punycode-encoded domain name labels to
820      the corresponding characters using the ToUnicode procedure. </t>
821</list></t>
822
823<t>This procedure will convert as many percent-encoded characters as
824possible to characters in an IRI. Because there are some choices when
825step 4 is applied (see <xref target="limitations"/>), results may
826vary.</t>
827
828<t>Conversions from URIs to IRIs MUST NOT use any character
829encoding other than UTF-8 in steps 3 and 4, even if it might be
830possible to guess from the context that another character encoding
831than UTF-8 was used in the URI.  For example, the URI
832"http://www.example.org/r%E9sum%E9.html" might with some guessing be
833interpreted to contain two e-acute characters encoded as
834iso-8859-1. It must not be converted to an IRI containing these
835e-acute characters. Otherwise, in the future the IRI will be mapped to
836"http://www.example.org/r%C3%A9sum%C3%A9.html", which is a different
837URI from "http://www.example.org/r%E9sum%E9.html".</t>
838
839<section title="Examples">
840
841<t>This section shows various examples of converting URIs to IRIs.
842Each example shows the result after each of the steps 1 through 6 is
843applied. XML Notation is used for the final result.  Octets are
844denoted by "&lt;" followed by two hexadecimal digits followed by
845"&gt;".</t>
846
847<t>The following example contains the sequence "%C3%BC", which is a
848strictly legal UTF-8 sequence, and which is converted into the actual
849character U+00FC, LATIN SMALL LETTER U WITH DIAERESIS (also known as
850u-umlaut).
851
852<list style="hanging">
853<t hangText="1.">http://www.example.org/D%C3%BCrst</t>
854<t hangText="2.">http://www.example.org/D&lt;c3&gt;&lt;bc&gt;rst</t>
855<t hangText="3.">http://www.example.org/D&lt;c3&gt;&lt;bc&gt;rst</t>
856<t hangText="4.">http://www.example.org/D&lt;c3&gt;&lt;bc&gt;rst</t>
857<t hangText="5.">http://www.example.org/D&amp;#xFC;rst</t>
858<t hangText="6.">http://www.example.org/D&amp;#xFC;rst</t>
859</list>
860</t>
861
862<t>The following example contains the sequence "%FC", which might
863represent U+00FC, LATIN SMALL LETTER U WITH DIAERESIS, in
864the<vspace/>iso-8859-1 character encoding.  (It might represent other
865characters in other character encodings. For example, the octet
866&lt;fc&gt; in iso-8859-5 represents U+045C, CYRILLIC SMALL LETTER
867KJE.)  Because &lt;fc&gt; is not part of a strictly legal UTF-8
868sequence, it is re-percent-encoded in step 3.
869
870
871<list style="hanging">
872<t hangText="1.">http://www.example.org/D%FCrst</t>
873<t hangText="2.">http://www.example.org/D&lt;fc&gt;rst</t>
874<t hangText="3.">http://www.example.org/D%FCrst</t>
875<t hangText="4.">http://www.example.org/D%FCrst</t>
876<t hangText="5.">http://www.example.org/D%FCrst</t>
877<t hangText="6.">http://www.example.org/D%FCrst</t>
878</list>
879</t>
880
881<t>The following example contains "%e2%80%ae", which is the percent-encoded<vspace/>UTF-8
882character encoding of U+202E, RIGHT-TO-LEFT OVERRIDE.
883The direct use of this character is forbiddin in an IRI. Therefore, the
884corresponding octets are re-percent-encoded in step 4. This example shows
885that the case (upper- or lowercase) of letters used in percent-encodings may not be preserved.
886The example also contains a punycode-encoded domain name label (xn--99zt52a),
887which is not converted.
888
889<list style="hanging">
890<t hangText="1.">http://xn--99zt52a.example.org/%e2%80%ae</t>
891<t hangText="2.">http://xn--99zt52a.example.org/&lt;e2&gt;&lt;80&gt;&lt;ae&gt;</t>
892<t hangText="3.">http://xn--99zt52a.example.org/&lt;e2&gt;&lt;80&gt;&lt;ae&gt;</t>
893<t hangText="4.">http://xn--99zt52a.example.org/%E2%80%AE</t>
894<t hangText="5.">http://xn--99zt52a.example.org/%E2%80%AE</t>
895<t hangText="6.">http://&amp;#x7D0D;&amp;#x8C46;.example.org/%E2%80%AE</t>
896</list></t>
897
898<t>Note that the label "xn--99zt52a" is converted to U+7D0D U+8C46
899(Japanese Natto). ((EDITOR NOTE: There is some inconsistency in this note.))</t>
900
901</section> <!-- examples -->
902</section> <!-- URItoIRI -->
903
904
905<section title="Use of IRIs" anchor="IRIuse">
906
907<section title="Limitations on UCS Characters Allowed in IRIs" anchor="limitations">
908
909<t>This section discusses limitations on characters and character
910sequences usable for IRIs beyond those given in <xref target="abnf"/>.
911The considerations in this section are
912relevant when IRIs are created and when URIs are converted to
913IRIs.</t>
914
915<t>
916
917<list style="hanging"><t hangText="a.">The repertoire of characters allowed
918    in each IRI component is limited by the definition of that component.
919    For example, the definition of the scheme component does not allow
920    characters beyond US-ASCII.
921    <vspace blankLines="1"/>
922    (Note: In accordance with URI practice, generic IRI
923    software cannot and should not check for such limitations.)</t>
924
925<t hangText="b.">The UCS contains many areas of characters for which
926    there are strong visual look-alikes. Because of the likelihood of
927    transcription errors, these also should be avoided. This includes
928    the full-width equivalents of Latin characters, half-width
929    Katakana characters for Japanese, and many others. It also
930    includes many look-alikes of "space", "delims", and "unwise",
931    characters excluded in <xref target="RFC3491"/>.</t>
932 
933<t hangText="c.">At the start of a component, the use of combining marks is strongly discouraged. As
934    an example, a COMBINING TILDE OVERLAY (U+0334) would be very confusing at the start of
935    a &lt;isegment>. Combined with the preceeding '/', it might look like a solidus
936    with combining tilde overlay, but IRI processing software will parse and process the
937    '/' separately.</t>
938<t hangText='d.'>The ZERO WIDTH NON-JOINER (U+200C) and ZERO WIDTH
939    JOINER (U+200D) are invisible in most contexts, but are crucial in
940    some very limited contexts. Appendix A of <xref target="RFC5892"/>
941    contains contextual restrictions for these and some other characters.
942    The use of these characters are strongly discouraged except
943    in the relevant contexts.</t>
944</list>
945</t>
946
947<t>Additional information is available from <xref target="UNIXML"/>.
948    <xref target="UNIXML"/> is written in the context of running text
949    rather than in that of identifiers. Nevertheless, it discusses
950    many of the categories of characters not appropriate for IRIs.</t>
951</section> <!-- limitations -->
952
953<section title="Software Interfaces and Protocols">
954
955<t>Although an IRI is defined as a sequence of characters, software
956interfaces for URIs typically function on sequences of octets or other
957kinds of code units. Thus, software interfaces and protocols MUST
958define which character encoding is used.</t>
959
960<t>Intermediate software interfaces between IRI-capable components and
961URI-only components MUST map the IRIs per <xref target="mapping"/>,
962when transferring from IRI-capable to URI-only components.
963
964This mapping SHOULD be applied as late as possible. It SHOULD NOT be
965applied between components that are known to be able to handle IRIs.</t>
966</section> <!-- software -->
967
968<section title="Format of URIs and IRIs in Documents and Protocols">
969
970<t>Document formats that transport URIs may have to be upgraded to allow
971the transport of IRIs. In cases where the document as a whole
972has a native character encoding, IRIs MUST also be encoded in this
973character encoding and converted accordingly by a parser or interpreter.
974
975IRI characters not expressible in the native character encoding SHOULD
976be escaped by using the escaping conventions of the document format if
977such conventions are available. Alternatively, they MAY be
978percent-encoded according to <xref target="mapping"/>. For example, in
979HTML or XML, numeric character references SHOULD be used. If a
980document as a whole has a native character encoding and that character
981encoding is not UTF-8, then IRIs MUST NOT be placed into the document
982in the UTF-8 character encoding.</t>
983
984<t>((UPDATE THIS NOTE)) Note: Some formats already accommodate IRIs,
985although they use different terminology. HTML 4.0 <xref
986target="HTML4"/> defines the conversion from IRIs to URIs as
987error-avoiding behavior. XML 1.0 <xref target="XML1"/>, XLink <xref
988target="XLink"/>, XML Schema <xref target="XMLSchema"/>, and
989specifications based upon them allow IRIs. Also, it is expected that
990all relevant new W3C formats and protocols will be required to handle
991IRIs <xref target="CharMod"/>.</t>
992
993</section> <!-- format -->
994
995<section title="Use of UTF-8 for Encoding Original Characters" anchor="UTF8use">
996
997<t>This section discusses details and gives examples for point c) in
998<xref target="Applicability"/>. To be able to use IRIs, the URI
999corresponding to the IRI in question has to encode original characters
1000into octets by using UTF-8.  This can be specified for all URIs of a
1001URI scheme or can apply to individual URIs for schemes that do not
1002specify how to encode original characters.  It can apply to the whole
1003URI, or only to some part. For background information on encoding
1004characters into URIs, see also Section 2.5 of <xref
1005target="RFC3986"/>.</t>
1006
1007<t>For new URI schemes, using UTF-8 is recommended in <xref
1008target="RFC4395bis"/>.  Examples where UTF-8 is already used are the URN
1009syntax <xref target="RFC2141"/>, IMAP URLs <xref target="RFC2192"/>,
1010POP URLs <xref target="RFC2384"/>, XMPP URLs <xref target='RFC5122'/>,
1011and the 'mailto:' scheme <xref target='RFC6068'/>. On the other hand, because the
1012HTTP URI scheme does not specify how to encode original characters,
1013only some HTTP URLs can have corresponding but different IRIs.</t>
1014
1015<t>For example, for a document with a URI
1016of<vspace/>"http://www.example.org/r%C3%A9sum%C3%A9.html", it is
1017possible to construct a corresponding IRI (in XML notation, see <xref
1018target="sec-Notation"/>):
1019"http://www.example.org/r&amp;#xE9;sum&amp;#xE9;.html" ("&amp;#xE9;"
1020stands for the e-acute character, and "%C3%A9" is the UTF-8 encoded
1021and percent-encoded representation of that character). On the other
1022hand, for a document with a URI of
1023"http://www.example.org/r%E9sum%E9.html", the percent-encoded octets
1024cannot be converted to actual characters in an IRI, as the
1025percent-encoding is not based on UTF-8.</t>
1026
1027<t>For most URI schemes, there is no need to upgrade their scheme
1028definition in order for them to work with IRIs.  The main case where
1029upgrading makes sense is when a scheme definition, or a particular
1030component of a scheme, is strictly limited to the use of US-ASCII
1031characters with no provision to include non-ASCII characters/octets
1032via percent-encoding, or if a scheme definition currently uses highly
1033scheme-specific provisions for the encoding of non-ASCII characters.</t>
1034
1035<t>This specification updates the IANA registry of URI schemes to note
1036their applicability to IRIs, see <xref target="iana"/>.  All IRIs use
1037URI schemes, and all URIs with URI schemes can be used as IRIs, even
1038though in some cases only by using URIs directly as IRIs, without any
1039conversion.</t>
1040
1041<t>Scheme definitions can impose restrictions on the syntax of
1042scheme-specific URIs; i.e., URIs that are admissible under the generic
1043URI syntax <xref target="RFC3986"/> may not be admissible due to
1044narrower syntactic constraints imposed by a URI scheme
1045specification. URI scheme definitions cannot broaden the syntactic
1046restrictions of the generic URI syntax; otherwise, it would be
1047possible to generate URIs that satisfied the scheme-specific syntactic
1048constraints without satisfying the syntactic constraints of the
1049generic URI syntax. However, additional syntactic constraints imposed
1050by URI scheme specifications are applicable to IRI, as the
1051corresponding URI resulting from the mapping defined in <xref
1052target="mapping"/> MUST be a valid URI under the syntactic
1053restrictions of generic URI syntax and any narrower restrictions
1054imposed by the corresponding URI scheme specification.</t>
1055
1056<t>The requirement for the use of UTF-8 generally applies to all parts
1057of a URI.  However, it is possible that the capability of IRIs to
1058represent a wide range of characters directly is used just in some
1059parts of the IRI (or IRI reference). The other parts of the IRI may
1060only contain US-ASCII characters, or they may not be based on
1061UTF-8. They may be based on another character encoding, or they may
1062directly encode raw binary data (see also <xref
1063target="RFC2397"/>). </t>
1064
1065<t>For example, it is possible to have a URI reference
1066of<vspace/>"http://www.example.org/r%E9sum%E9.xml#r%C3%A9sum%C3%A9",
1067where the document name is encoded in iso-8859-1 based on server
1068settings, but where the fragment identifier is encoded in UTF-8 according
1069to <xref target="XPointer"/>. The IRI corresponding to the above
1070URI would be (in XML notation)<vspace/>"http://www.example.org/r%E9sum%E9.xml#r&amp;#xE9;sum&amp;#xE9;".</t>
1071
1072<t>Similar considerations apply to query parts. The functionality
1073of IRIs (namely, to be able to include non-ASCII characters) can
1074only be used if the query part is encoded in UTF-8.</t>
1075
1076</section> <!-- utf8 -->
1077
1078<section title="Relative IRI References">
1079<t>Processing of relative IRI references against a base is handled
1080straightforwardly; the algorithms of <xref target="RFC3986"/> can
1081be applied directly, treating the characters additionally allowed
1082in IRI references in the same way that unreserved characters are treated in URI
1083references.</t>
1084
1085</section> <!-- relative -->
1086</section> <!-- IRIuse -->
1087
1088  <section title="Legacy Extended IRIs (LEIRIs)">
1089    <t>In some cases, there have been formats which have used a protocol element
1090      which is a variant of the IRI definition; these variants have usually been
1091      somewhat less restricted in syntax. This section provides
1092      a definition and a name (Legacy Extended IRI or LEIRI) for one of these
1093      variants used widely in XML-based protocols. This variant has to be used with care;
1094      it requires further processing before being fully interchangeable as IRIs.
1095
1096      New protocols and formats SHOULD NOT use Legacy Extended IRIs.
1097      Even where Legacy Extended IRIs are allowed, only IRIs fully conforming
1098      to the syntax definition in <xref target="abnf"></xref> SHOULD be created,
1099      generated, and used. The provisions in this section also apply to
1100      Legacy Extended IRI references.</t>
1101   
1102    <section title="Legacy Extended IRI Syntax">
1103      <figure>
1104
1105        <preamble>This section defines Legacy Extended IRIs (LEIRIs).  The syntax of
1106   Legacy Extended IRIs is the same as that for &lt;IRI-reference&gt;, except
1107   that the ucschar production is replaced by the leiri-ucschar
1108   production:
1109
1110</preamble>
1111        <artwork>
1112leiri-ucschar  = " " / "&lt;" / "&gt;" / '"' / "{" / "}" / "|"
1113               / "\" / "^" / "`" / %x0-1F / %x7F-D7FF
1114               / %xE000-FFFD / %x10000-10FFFF
1115        </artwork>
1116        <postamble>The restriction on bidirectional formatting characters in <xref target="Bidi"></xref> is lifted.
1117        The iprivate production becomes redundant.</postamble>
1118      </figure>
1119
1120      <t>Likewise, the syntax for Legacy Extended IRI references
1121      (LEIRI references) is the same as that for IRI references with
1122      the above replacement of ucschar with leiri-ucschar.</t>
1123
1124     </section>
1125    <section title="Conversion of Legacy Extended IRIs to IRIs" anchor="LEIRIspec">
1126      <t>To convert a Legacy Extended IRI (reference) to
1127      an IRI (reference), each character allowed in a Legacy Extended IRI (reference)
1128      but not allowed in an IRI (reference) (see <xref target="notAllowed"></xref>)  MUST be percent-encoded
1129      by applying the steps in <xref target="compmapping"></xref>.</t>
1130    </section>
1131     
1132    <section title="Characters Allowed in Legacy Extended IRIs but not in IRIs" anchor="notAllowed">
1133      <t>This section provides a list of the groups of characters and code points
1134        that are allowed in Legacy Extedend IRIs, but are not allowed in IRIs
1135        or are allowed in IRIs only in the query part. For each group of characters,
1136        advice on the usage of these characters is also given, concentrating on the
1137        reasons for why not to use them.</t>
1138      <t>
1139        <list>
1140          <t>Space (U+0020): Some formats and applications use space as a delimiter,
1141            e.g., for items in a list. Appendix C of <xref target="RFC3986"></xref>
1142            also mentions that white space may have to be added when displaying
1143            or printing long URIs; the same applies to long IRIs.
1144            Spaces might disappear, or a single Legacy Extended IRI
1145            might incorrectly be interpreted as two or more separate ones.</t>
1146     
1147          <t>Delimiters "&lt;" (U+003C), "&gt;" (U+003E), and '"' (U+0022):
1148            Appendix C of <xref target="RFC3986"></xref> suggests the use of
1149            double-quotes ("http://example.com/") and angle brackets
1150        (&lt;http://example.com/&gt;) as delimiters for URIs in plain text.
1151        These conventions are often used, and also apply to IRIs.
1152        Legacy Extended IRIs using these characters might be cut off at the wrong place.</t>
1153     
1154          <t>Unwise characters "\" (U+005C),
1155          "^" (U+005E), "`" (U+0060), "{" (U+007B), "|" (U+007C), and "}" (U+007D):
1156          These characters originally were excluded from URIs because
1157          the respective codepoints are assigned to different graphic characters
1158          in some 7-bit or 8-bit encoding. Despite the move to Unicode,
1159          some of these characters are still occasionally displayed differently
1160          on some systems, e.g., U+005C as a Japanese Yen symbol.
1161     
1162          Also, the fact that these characters are not used in URIs or IRIs
1163          has encouraged their use outside URIs or IRIs in contexts that may
1164          include URIs or IRIs. In case a Legacy Extended IRI with such a character
1165          is used in such a context, the Legacy Extended IRI will be interpreted piecemeal.</t>
1166     
1167          <t>The controls (C0 controls, DEL, and C1 controls, #x0  - #x1F  #x7F - #x9F):
1168            There is no way to transmit these characters reliably except potentially
1169            in electronic form. Even when in electronic form, some software components
1170            might silently filter out some of these characters,
1171            or may stop processing alltogether when encountering some of them.
1172            These characters may affect text display in subtle, unnoticable ways
1173            or in drastic, global, and irreversible ways depending
1174            on the hardware and software involved.
1175            The use of some of these characters may allow malicious users
1176            to manipulate the display of a Legacy Extended IRI and its context.</t>
1177          <t>Bidi formatting characters (U+200E, U+200F, U+202A-202E):
1178            These characters affect the display ordering of characters.
1179            Displayed Legacy Extended IRIs containing these characters
1180            cannot be converted back to electronic form (logical order) unambiguously.
1181            These characters may allow malicious users to manipulate
1182            the display of a Legacy Extended IRI and its context.</t>
1183          <t>Specials (U+FFF0-FFFD): These code points provide functionality
1184            beyond that useful in a Legacy Extended IRI, for example byte order identification,
1185            annotation, and replacements for unknown characters and objects.
1186            Their use and interpretation in a Legacy Extended IRI
1187            serves no purpose and may lead to confusing display variations.</t>
1188          <t>Private use code points (U+E000-F8FF, U+F0000-FFFFD, U+100000-10FFFD):
1189            Display and interpretation of these code points is by definition
1190            undefined without private agreement. Therefore, these code points
1191            are not suited for use on the Internet. They are not interoperable and may have
1192            unpredictable effects.</t>
1193          <t>Tags (U+E0000-E0FFF): These characters provide a way to language tag in Unicode plain text.
1194            They are not appropriate for Legacy Extended IRIs because language information
1195            in identifiers cannot reliably be input, transmitted
1196            (e.g., on a visual medium such as paper), or recognized.</t>
1197          <t>Non-characters (U+FDD0-FDEF, U+1FFFE-1FFFF, U+2FFFE-2FFFF, U+3FFFE-3FFFF,
1198            U+4FFFE-4FFFF, U+5FFFE-5FFFF, U+6FFFE-6FFFF, U+7FFFE-7FFFF, U+8FFFE-8FFFF,
1199            U+9FFFE-9FFFF, U+AFFFE-AFFFF, U+BFFFE-BFFFF, U+CFFFE-CFFFF, U+DFFFE-DFFFF,
1200            U+EFFFE-EFFFF, U+FFFFE-FFFFF, U+10FFFE-10FFFF):
1201            These code points are defined as non-characters. Applications may use
1202            some of them internally, but are not prepared to interchange them.</t>
1203        </list>
1204      </t>
1205      <t>For reference, we here also list the code points and code units
1206        not even allowed in Legacy Extended IRIs:
1207        <list>
1208         
1209          <t>Surrogate code units (D800-DFFF):
1210          These do not represent Unicode codepoints.</t>
1211           <t>Non-characters (U+FFFE-FFFF): These are not allowed in XML nor LEIRIs.</t>
1212     
1213        </list>
1214      </t>
1215    </section>
1216  </section>
1217 
1218<section title="URI/IRI Processing Guidelines (Informative)" anchor="guidelines">
1219
1220<t>This informative section provides guidelines for supporting IRIs in
1221the same software components and operations that currently process
1222URIs: Software interfaces that handle URIs, software that allows users
1223to enter URIs, software that creates or generates URIs, software that
1224displays URIs, formats and protocols that transport URIs, and software
1225that interprets URIs. These may all require modification before
1226functioning properly with IRIs. The considerations in this section
1227also apply to URI references and IRI references.</t>
1228
1229<section title="URI/IRI Software Interfaces">
1230<t>Software interfaces that handle URIs, such as URI-handling APIs and
1231protocols transferring URIs, need interfaces and protocol elements
1232that are designed to carry IRIs.</t>
1233
1234<t>In case the current handling in an API or protocol is based on
1235US-ASCII, UTF-8 is recommended as the character encoding for IRIs, as
1236it is compatible with US-ASCII, is in accordance with the
1237recommendations of <xref target="RFC2277"/>, and makes converting to
1238URIs easy. In any case, the API or protocol definition must clearly
1239define the character encoding to be used.</t>
1240
1241<t>The transfer from URI-only to IRI-capable components requires no
1242mapping, although the conversion described in <xref
1243target="URItoIRI"/> above may be performed. It is preferable not to
1244perform this inverse conversion unless it is certain this can be done
1245correctly.</t>
1246</section><!-- software interfaces -->
1247
1248<section title="URI/IRI Entry">
1249
1250<t>Some components allow users to enter URIs into the system
1251by typing or dictation, for example. This software must be updated to allow
1252for IRI entry.</t>
1253
1254<t>A person viewing a visual presentation of an IRI (as a sequence
1255of glyphs, in some order, in some visual display)
1256will use an entry method for characters in the user's language to
1257input the IRI. Depending on the script and the input method used, this
1258may be a more or less complicated process.</t>
1259
1260<t>The process of IRI entry must ensure, as much as possible, that the
1261restrictions defined in <xref target="abnf"/> are met. This may be
1262done by choosing appropriate input methods or variants/settings
1263thereof, by appropriately converting the characters being input, by
1264eliminating characters that cannot be converted, and/or by issuing a
1265warning or error message to the user.</t>
1266
1267<t>As an example of variant settings, input method editors for East
1268Asian Languages usually allow the input of Latin letters and related
1269characters in full-width or half-width versions. For IRI input, the
1270input method editor should be set so that it produces half-width Latin
1271letters and punctuation and full-width Katakana.</t>
1272
1273<t>An input field primarily or solely used for the input of URIs/IRIs
1274might allow the user to view an IRI as it is mapped to a URI.  Places
1275where the input of IRIs is frequent may provide the possibility for
1276viewing an IRI as mapped to a URI. This will help users when some of
1277the software they use does not yet accept IRIs.</t>
1278
1279<t>An IRI input component interfacing to components that handle URIs,
1280but not IRIs, must map the IRI to a URI before passing it to these
1281components.</t>
1282
1283<t>For the input of IRIs with right-to-left characters, please see
1284<xref target="Bidi"></xref>.</t>
1285</section><!-- entry -->
1286
1287<section title="URI/IRI Transfer between Applications">
1288
1289<t>Many applications (for example, mail user agents) try to detect
1290URIs appearing in plain text. For this, they use some heuristics based
1291on URI syntax. They then allow the user to click on such URIs and
1292retrieve the corresponding resource in an appropriate (usually
1293scheme-dependent) application.</t>
1294
1295<t>Such applications would need to be upgraded, in order to use the
1296IRI syntax as a base for heuristics. In particular, a non-ASCII
1297character should not be taken as the indication of the end of an IRI.
1298Such applications also would need to make sure that they correctly
1299convert the detected IRI from the character encoding of the document
1300or application where the IRI appears, to the character encoding used
1301by the system-wide IRI invocation mechanism, or to a URI (according to
1302<xref target="mapping"/>) if the system-wide invocation mechanism only
1303accepts URIs.</t>
1304
1305<t>The clipboard is another frequently used way to transfer URIs and
1306IRIs from one application to another. On most platforms, the clipboard
1307is able to store and transfer text in many languages and scripts.
1308Correctly used, the clipboard transfers characters, not octets, which
1309will do the right thing with IRIs.</t>
1310</section><!-- transfer -->
1311
1312<section title="URI/IRI Generation">
1313
1314<t>Systems that offer resources through the Internet, where those
1315resources have logical names, sometimes automatically generate URIs
1316for the resources they offer. For example, some HTTP servers can
1317generate a directory listing for a file directory and then respond to
1318the generated URIs with the files.</t>
1319
1320<t>Many legacy character encodings are in use in various file systems.
1321Many currently deployed systems do not transform the local character
1322representation of the underlying system before generating URIs.</t>
1323
1324<t>For maximum interoperability, systems that generate resource
1325identifiers should make the appropriate transformations. For example,
1326if a file system contains a file named
1327"r&amp;#xE9;sum&amp;#xE9;.html", a server should expose this as
1328"r%C3%A9sum%C3%A9.html" in a URI, which allows use of
1329"r&amp;#xE9;sum&amp;#xE9;.html" in an IRI, even if locally the file
1330name is kept in a character encoding other than UTF-8.
1331</t>
1332
1333<t>This recommendation particularly applies to HTTP servers. For FTP
1334servers, similar considerations apply; see <xref target="RFC2640"/>.</t>
1335</section><!-- generation -->
1336
1337<section title="URI/IRI Selection" anchor="selection">
1338<t>In some cases, resource owners and publishers have control over the
1339IRIs used to identify their resources. This control is mostly
1340executed by controlling the resource names, such as file names,
1341directly.</t>
1342
1343<t>In these cases, it is recommended to avoid choosing IRIs that are
1344easily confused. For example, for US-ASCII, the lower-case ell ("l") is
1345easily confused with the digit one ("1"), and the upper-case oh ("O") is
1346easily confused with the digit zero ("0"). Publishers should avoid
1347confusing users with "br0ken" or "1ame" identifiers.</t>
1348
1349<t>Outside the US-ASCII repertoire, there are many more opportunities for
1350confusion; a complete set of guidelines is too lengthy to include
1351here. As long as names are limited to characters from a single script,
1352native writers of a given script or language will know best when
1353ambiguities can appear, and how they can be avoided. What may look
1354ambiguous to a stranger may be completely obvious to the average
1355native user. On the other hand, in some cases, the UCS contains
1356variants for compatibility reasons; for example, for typographic purposes.
1357These should be avoided wherever possible. Although there may be exceptions,
1358newly created resource names should generally be in NFKC
1359<xref target="UTR15"></xref> (which means that they are also in NFC).</t>
1360
1361<t>As an example, the UCS contains the "fi" ligature at U+FB01
1362for compatibility reasons.
1363Wherever possible, IRIs should use the two letters "f" and "i" rather
1364than the "fi" ligature. An example where the latter may be used is
1365in the query part of an IRI for an explicit search for a word written
1366containing the "fi" ligature.</t>
1367
1368<t>In certain cases, there is a chance that characters from different
1369scripts look the same. The best known example is the similarity of the
1370Latin "A", the Greek "Alpha", and the Cyrillic "A". To avoid such
1371cases, IRIs should only be created where all the characters in a
1372single component are used together in a given language. This usually
1373means that all of these characters will be from the same script, but
1374there are languages that mix characters from different scripts (such
1375as Japanese).  This is similar to the heuristics used to distinguish
1376between letters and numbers in the examples above. Also, for Latin,
1377Greek, and Cyrillic, using lowercase letters results in fewer
1378ambiguities than using uppercase letters would.</t>
1379</section><!-- selection -->
1380
1381<section title="Display of URIs/IRIs" anchor="display">
1382<t>
1383In situations where the rendering software is not expected to display
1384non-ASCII parts of the IRI correctly using the available layout and font
1385resources, these parts should be percent-encoded before being displayed.</t>
1386
1387<t>For display of Bidi IRIs, please see <xref target="Bidi"/>.</t>
1388</section> <!-- display -->
1389
1390<section title="Interpretation of URIs and IRIs">
1391<t>Software that interprets IRIs as the names of local resources should
1392accept IRIs in multiple forms and convert and match them with the
1393appropriate local resource names.</t>
1394
1395<t>First, multiple representations include both IRIs in the native
1396character encoding of the protocol and also their URI counterparts.</t>
1397
1398<t>Second, it may include URIs constructed based on character
1399encodings other than UTF-8. These URIs may be produced by user agents that do
1400not conform to this specification and that use legacy character encodings to
1401convert non-ASCII characters to URIs. Whether this is necessary, and what
1402character encodings to cover, depends on a number of factors, such as
1403the legacy character encodings used locally and the distribution of
1404various versions of user agents. For example, software for Japanese
1405may accept URIs in Shift_JIS and/or EUC-JP in addition to UTF-8.</t>
1406
1407<t>Third, it may include additional mappings to be more user-friendly
1408and robust against transmission errors. These would be similar to how
1409some servers currently treat URIs as case insensitive or perform
1410additional matching to account for spelling errors. For characters
1411beyond the US-ASCII repertoire, this may, for example, include
1412ignoring the accents on received IRIs or resource names. Please note
1413that such mappings, including case mappings, are language
1414dependent.</t>
1415
1416<t>It can be difficult to identify a resource unambiguously if too
1417many mappings are taken into consideration. However, percent-encoded
1418and not percent-encoded parts of IRIs can always be clearly distinguished.
1419Also, the regularity of UTF-8 (see <xref target="Duerst97"/>) makes the
1420potential for collisions lower than it may seem at first.</t>
1421</section> <!-- interpretation -->
1422
1423<section title="Upgrading Strategy">
1424<t>Where this recommendation places further constraints on software
1425for which many instances are already deployed, it is important to
1426introduce upgrades carefully and to be aware of the various
1427interdependencies.</t>
1428
1429<t>If IRIs cannot be interpreted correctly, they should not be created,
1430generated, or transported. This suggests that upgrading URI interpreting
1431software to accept IRIs should have highest priority.</t>
1432
1433<t>On the other hand, a single IRI is interpreted only by a single or
1434very few interpreters that are known in advance, although it may be
1435entered and transported very widely.</t>
1436
1437<t>Therefore, IRIs benefit most from a broad upgrade of software to be
1438able to enter and transport IRIs. However, before an
1439individual IRI is published, care should be taken to upgrade the corresponding
1440interpreting software in order to cover the forms expected to be
1441received by various versions of entry and transport software.</t>
1442
1443<t>The upgrade of generating software to generate IRIs instead of using a
1444local character encoding should happen only after the service is upgraded
1445to accept IRIs. Similarly, IRIs should only be generated when the service
1446accepts IRIs and the intervening infrastructure and protocol is known
1447to transport them safely.</t>
1448
1449<t>Software converting from URIs to IRIs for display should be upgraded
1450only after upgraded entry software has been widely deployed to the
1451population that will see the displayed result.</t>
1452
1453
1454<t>Where there is a free choice of character encodings, it is often
1455possible to reduce the effort and dependencies for upgrading to IRIs
1456by using UTF-8 rather than another encoding. For example, when a new
1457file-based Web server is set up, using UTF-8 as the character encoding
1458for file names will make the transition to IRIs easier. Likewise, when
1459a new Web form is set up using UTF-8 as the character encoding of the
1460form page, the returned query URIs will use UTF-8 as the character
1461encoding (unless the user, for whatever reason, changes the character
1462encoding) and will therefore be compatible with IRIs.</t>
1463
1464
1465<t>These recommendations, when taken together, will allow for the
1466extension from URIs to IRIs in order to handle characters other than
1467US-ASCII while minimizing interoperability problems. For
1468considerations regarding the upgrade of URI scheme definitions, see
1469<xref target="UTF8use"/>.</t>
1470
1471</section> <!-- upgrading -->
1472</section> <!-- guidelines -->
1473
1474<section title="IANA Considerations" anchor="iana">
1475
1476<t>NOTE: THIS SECTION NEEDS REVIEW AGAINST HAPPIANA WORK.</t>
1477
1478<t>RFC Editor and IANA note: Please Replace RFC XXXX with the
1479number of this document when it issues as an RFC, and RFC YYYY
1480with the number of the RFC issued for draft-ietf-iri-rfc3987bis. </t>
1481
1482<t>IANA maintains a registry of "URI schemes".  This document attempts
1483to make it clear from the registry that a "URI scheme" also serves an
1484"IRI scheme", and makes several changes to the registry. </t>
1485
1486<t>The description of the registry should be changed: "RFC 4395
1487defined an IANA-maintained registry of URI Schemes. RFC XXXX updates
1488this registry to make it clear that the registered values also serve
1489as IRI schemes, as defined in RFC YYYY." </t>
1490
1491<t>The registry includes schemes marked as Permanent or Provisional.
1492Previously, this was accomplished by having two sections, "Permanent"
1493and "Provisional". However, in order to allow other status
1494("Historical", and possibly a Proposed status for proposals which have
1495been received but not accepted), the registry should be changed so
1496that the status is indicated in a separate "Status" column, whose
1497values may be "Permanent", "Provisional" or "Historical".
1498Changes in status as well as updates to the entire registration
1499may be accomplished by requests and expert review.
1500</t>
1501
1502
1503</section> <!-- IANA -->
1504   
1505<section title="Security Considerations" anchor="security">
1506<t>The security considerations discussed in <xref target="RFC3986"/>
1507also apply to IRIs. In addition, the following issues require
1508particular care for IRIs.</t>
1509<t>Incorrect encoding or decoding can lead to security problems.
1510For example, some UTF-8 decoders do not check against overlong
1511byte sequences. See <xref target='UTR36'/> Section 3 for details.</t>
1512
1513  <t>There are serious difficulties with relying on a human to verify that a
1514    an IRI (whether presented visually or aurally)
1515    is the same as another IRI or is the one intended.
1516    These problems exist with ASCII-only URIs (bl00mberg.com vs. bloomberg.com)
1517    but are strongly exacerbated when using the much larger character repertoire of Unicode.
1518    For details, see Section 2 of <xref target='UTR36'/>.
1519    Using administrative and technical means to reduce the availability
1520    of such exploits is possible, but they are difficult to eliminate altogether.
1521    User agents SHOULD NOT rely on visual or perceptual comparison or verification of IRIs
1522    as a means of validating or assuring safety, correctness or appropriateness of an IRI.
1523    Other means of presenting users with the validity, safety, or appropriateness
1524    of visited sites are being developed in the browser community
1525    as an alternative means of avoiding these difficulties.</t>
1526
1527<t>Besides the large character repertoire of Unicode, reasons for
1528  confusion include different forms of normalization and different normalization
1529  expectations, use of percent-encoding with various legacy encodings,
1530  and bidirectionality issues. See also <xref target="Bidi"/>.</t>
1531
1532<t>Confusion can occur in various IRI components, such as the
1533domain name part or the path part, or between IRI components. For considerations specific
1534to the domain name part, see <xref target="RFC5890"/>. For considerations specific to
1535particular protocols or schemes, see the security sections of the relevant specifications
1536and registration templates.
1537Administrators of sites that allow independent
1538users to create resources in the same sub area have to be careful.
1539Details are discussed in <xref target="selection"/>.</t>
1540
1541  <t>The characters additionally allowed in Legacy Extended IRIs
1542    introduce additional security issues. For details, see <xref target='notAllowed'/>.</t>
1543</section><!-- security -->
1544
1545<section title="Acknowledgements">
1546<t>This document was derived from <xref target="RFC3987"/>; the acknowledgments from
1547that specification still apply.</t>
1548<t>In addition, this document was influenced by contributions from (in no particular order)
1549  Norman Walsh, Richard Tobin,
1550  Henry S. Thomson, John Cowan, Paul Grosso, the XML Core Working Group of the W3C,
1551  Chris Lilley, Bjoern Hoehrmann,
1552Felix Sasaki, Jeremy Carroll, Frank Ellermann, Michael Everson, Cary Karp, Matitiahu Allouche,
1553Richard Ishida, Addison Phillips, Jonathan Rosenne, Najib Tounsi, Debbie Garside, Mark Davis, Sarmad
1554Hussain, Ted Hardie, Konrad Lanz, Thomas Roessler, Lisa Dusseault, Julian Reschke, Giovanni
1555Campagna, Anne van Kesteren, Mark Nottingham, Erik van der Poel, Marcin Hanclik, Marcos Caceres, Roy
1556Fielding, Greg Wilkins, Pieter Hintjens, Daniel R. Tobias, Marko Martin, Maciej Stanchowiak, Wil
1557Tan, Yui Naruse, Michael A. Puls II, Dave Thaler, Tom Petch, John Klensin, Shawn Steele, Peter
1558Saint-Andre, Geoffrey Sneddon, Chris Weber, Alex Melnikov, Slim Amamou, S. Moonesamy, Tim Berners-Lee, Yaron
1559Goland, Sam Ruby, Adam Barth, Abdulrahman I. ALGhadir, Aharon Lanin, Thomas Milo, Murray Sargent,
1560Marc Blanchet, and Mykyta Yevstifeyev.</t>
1561</section> <!-- Acknowledgements -->
1562
1563<section title="Main Changes Since RFC 3987">
1564  <t>This section describes the main changes since <xref target="RFC3987"></xref>.</t>
1565  <section title="Split out Bidi, processing guidelines, comparison sections">
1566    <t>Move some components (comparison, bidi, processing) into separate documents.</t>
1567  </section>
1568  <section title="Major restructuring of IRI processing model" anchor="forkChanges">
1569    <t>Major restructuring of IRI processing model to make scheme-specific translation
1570      necessary to handle IDNA requirements and for consistency with web implementations. </t>
1571    <t>Starting with IRI, you want one of:
1572      <list style="hanging">
1573        <t hangText="a"> IRI components (IRI parsed into UTF8 pieces)</t>
1574        <t hangText="b"> URI components (URI parsed into ASCII pieces, encoded correctly) </t>
1575        <t hangText="c"> whole URI  (for passing on to some other system that wants whole URIs) </t>
1576      </list></t>
1577   
1578    <section title="OLD WAY">
1579      <t><list style="numbers">
1580       
1581        <t>Pct-encoding on the whole thing to a URI.
1582          (c1) If you want a (maybe broken) whole URI, you might
1583          stop here.</t>
1584       
1585        <t>Parsing the URI into URI components.
1586          (b1) If you want (maybe broken) URI components, stop here.</t>
1587       
1588        <t> Decode the components (undoing the pct-encoding).
1589          (a) if you want IRI components, stop here.</t>
1590       
1591        <t> reencode:  Either using a different encoding some components
1592          (for domain names, and query components in web pages, which
1593          depends on the component, scheme and context), and otherwise
1594          using pct-encoding.
1595          (b2) if you want (good) URI components, stop here.</t>
1596       
1597        <t> reassemble the reencoded components.
1598          (c2) if you want a (*good*) whole URI stop here.</t>
1599      </list>
1600       
1601      </t>
1602     
1603    </section>
1604   
1605    <section title="NEW WAY">
1606      <t>
1607        <list style="numbers">
1608         
1609          <t> Parse the IRI into IRI components using the generic syntax.
1610            (a) if you want IRI components, stop here.</t>
1611         
1612          <t> Encode each components, using pct-encoding, IDN encoding, or
1613            special query part encoding depending on the component
1614            scheme or context. (b) If you want URI components, stop here.</t>
1615          <t> reassemble the a whole URI from URI components.
1616            (c) if you want a whole URI stop here.</t>
1617        </list></t>
1618    </section>
1619    <section title="Extension of Syntax">
1620      <t>Added the tag range (U+E0000-E0FFF) to the iprivate production.
1621        Some IRIs generated with the new syntax may fail to pass very strict checks
1622        relying on the old syntax. But characters in this range should be extremely infrequent
1623        anyway.</t>
1624    </section>
1625    <section title="More to be added"><t>TODO: There are more main changes that need to be
1626      documented in this section.</t></section>
1627</section>
1628
1629<section title="Change Log">
1630
1631<t>Note to RFC Editor: Please completely remove this section before publication.</t>
1632
1633<section title='Changes after draft-ietf-iri-3987bis-01'>
1634    <t>Changes from draft-ietf-iri-3987bis-01 onwards are available as changesets
1635      in the IETF tools subversion repository at
1636      http://trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis/draft-ietf-iri-3987bis.xml.</t>
1637</section>
1638 
1639<section title='Changes from draft-duerst-iri-bis-07 to draft-ietf-iri-3987bis-00'>
1640     <t>Changed draft name, date, last paragraph of abstract, and titles in change log, and added this section
1641     in moving from draft-duerst-iri-bis-07 (personal submission) to draft-ietf-iri-3987bis-00 (WG document).</t>
1642</section>
1643
1644<section title="Changes from -06 to -07 of draft-duerst-iri-bis">
1645  <t>Major restructuring of the processing model, see <xref target="forkChanges"></xref>.</t>
1646</section>
1647</section>
1648
1649<section title='Changes from -00 to -01'><t><list style="symbols">
1650  <t>Removed 'mailto:' before mail addresses of authors.</t>
1651  <t>Added "&lt;to be done&gt;" as right side of 'href-strip' rule. Fixed '|' to '/' for
1652    alternatives.</t>
1653</list></t>
1654</section>
1655
1656<section title="Changes from -05 to -06 of draft-duerst-iri-bis-00"><t><list style="symbols">
1657<t>Add HyperText Reference, change abstract, acks and references for it</t>
1658<t>Add Masinter back as another editor.</t>
1659<t>Masinter integrates HRef material from HTML5 spec.</t>
1660<t>Rewrite introduction sections to modernize.</t>
1661</list></t>
1662</section>
1663
1664<section title="Changes from -04 to -05 of draft-duerst-iri-bis">
1665  <t><list style="symbols">
1666    <t>Updated references.</t>
1667    <t>Changed IPR text to pre5378Trust200902.</t></list></t>
1668</section>
1669
1670<section title="Changes from -03 to -04 of draft-duerst-iri-bis">
1671  <t><list style="symbols">
1672    <t>Added explicit abbreviation for LEIRIs.</t>
1673    <t>Mentioned LEIRI references.</t>
1674    <t>Completed text in LEIRI section about tag characters and about specials.</t></list></t>
1675</section>
1676
1677<section title="Changes from -02 to -03 of draft-duerst-iri-bis">
1678  <t><list style="symbols">
1679    <t>Updated some references.</t>
1680    <t>Updated Michel Suginard's coordinates.</t></list></t>
1681</section>
1682
1683<section title="Changes from -01 to -02 of draft-duerst-iri-bis">
1684  <t><list style="symbols">
1685    <t>Added tag range to iprivate (issue private-include-tags-115).</t>
1686    <t>Added Specials (U+FFF0-FFFD) to Legacy Extended IRIs.</t></list></t>
1687</section>
1688<section title="Changes from -00 to -01 of draft-duerst-iri-bis">
1689  <t><list style="symbols">
1690    <t>Changed from "IRIs with Spaces/Controls" to "Legacy Extended IRI"
1691      based on input from the W3C XML Core WG.
1692      Moved the relevant subsections to the back and promoted them to a section.</t>
1693    <t>Added some text re. Legacy Extended IRIs to the security section.</t>
1694    <t>Added a IANA Consideration Section.</t>
1695    <t>Added this Change Log Section.</t>
1696    <t>Added a section about "IRIs with Spaces/Controls" (converting from a Note in RFC 3987).</t></list></t>
1697</section> <!-- -00 to -01 -->
1698<section title="Changes from RFC 3987 to -00 of draft-duerst-iri-bis">
1699  <t><list>
1700    <t>Fixed errata (see http://www.rfc-editor.org/cgi-bin/errataSearch.pl?rfc=3987).</t></list></t>
1701</section> <!-- from 3987 -->
1702</section>
1703</middle>
1704
1705<back>
1706<references title="Normative References">
1707
1708<reference anchor="ASCII">
1709<front>
1710<title>Coded Character Set -- 7-bit American Standard Code for Information
1711Interchange</title>
1712<author>
1713<organization>American National Standards Institute</organization>
1714</author>
1715<date year="1986"/>
1716</front>
1717<seriesInfo name="ANSI" value="X3.4"/>
1718</reference>
1719
1720  <reference anchor="ISO10646" target='http://standards.iso.org/ittf/PubliclyAvailableStandards/c051273_ISO_IEC_10646_2011(E).zip'>
1721<front>
1722<title>ISO/IEC 10646:2011: Information Technology -
1723Universal Multiple-Octet Coded Character Set (UCS)</title>
1724<author>
1725<organization>International Organization for Standardization</organization>
1726</author>
1727<date month="March" year="20011"/>
1728</front>
1729<seriesInfo name="ISO" value="Standard 10646"/>
1730</reference>
1731
1732&rfc2119;
1733&rfc3491;
1734
1735  <reference anchor="STD63">
1736    <front>
1737      <title abbrev="UTF-8">UTF-8, a transformation format of ISO 10646</title>
1738      <author initials="F." surname="Yergeau" ifullname="François Yergeau" fullname="Francois Yergeau"></author>
1739      <date month="November" year="2003"/>
1740    </front>
1741    <seriesInfo name="STD" value="63"/>
1742    <seriesInfo name="RFC" value="3629"/>
1743   
1744  </reference>
1745 
1746&rfc3986;
1747
1748<reference anchor="STD68">
1749<front>
1750<title abbrev="ABNF">Augmented BNF for Syntax Specifications: ABNF</title>
1751<author initials="D." surname="Crocker" fullname="Dave Crocker"><organization/></author>
1752<author initials="P." surname="Overell" fullname="Paul Overell"><organization/></author>
1753<date month="January" year="2008"/></front>
1754<seriesInfo name="STD" value="68"/><seriesInfo name="RFC" value="5234"/>
1755</reference>
1756 
1757&rfc5890;
1758&rfc5891;
1759
1760  <reference anchor="RFC5892">
1761    <front>
1762      <title>The Unicode Code Points and Internationalized Domain Names for Applications (IDNA)</title>
1763      <author initials="P." surname="Faltstrom" isurname="Fältström" fullname="P. Faltstrom" ifullname="P. Fältström">
1764        <organization/>
1765      </author>
1766      <date year="2010" month="August"/>
1767    </front>
1768    <seriesInfo name="RFC" value="5892"/>
1769    <format type="TXT" octets="187370" target="http://www.rfc-editor.org/rfc/rfc5892.txt"/>
1770  </reference>
1771
1772<reference anchor="UNIV6">
1773<front>
1774<title>The Unicode Standard, Version 6.1.0 (Mountain View, CA, The Unicode Consortium, 2012, ISBN 978-1-936213-02-3)</title>
1775<author><organization>The Unicode Consortium</organization></author>
1776<date year="2012" />
1777</front>
1778</reference>
1779
1780<reference anchor="UTR15" target="http://www.unicode.org/unicode/reports/tr15/tr15-23.html">
1781<front>
1782<title>Unicode Normalization Forms</title>
1783<author initials="M." surname="Davis" fullname="Mark Davis"><organization/></author>
1784  <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"><organization/></author>
1785<date year="2008" month="March"/>
1786</front>
1787<seriesInfo name="Unicode Standard Annex" value="#15"/>
1788</reference>
1789
1790</references>
1791
1792<references title="Informative References">
1793
1794  <reference anchor='CharMod' target='http://www.w3.org/TR/2004/CR-charmod-resid/'>
1795    <front>
1796      <title>Character Model for the World Wide Web 1.0: Resource Identifiers</title>
1797      <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"/>
1798      <author initials="F." surname="Yergeau" ifullname="François Yergeau" fullname="Francois Yergeau"></author>
1799      <author fullname='Richard Ishida' surname='Ishida' initials='R. '/>
1800      <author fullname='Misha Wolf' surname='Wolf' initials='M. '/>
1801      <author fullname='Tex Texin' surname='Texin' initials='T. '/>
1802      <date year='2004' month='November' day='22'/>
1803    </front>
1804    <seriesInfo name='W3C Candidate Recommendation' value='CR-charmod-resid-20041122'/>
1805  </reference>
1806
1807<reference anchor="Duerst97" target="http://www.ifi.unizh.ch/mml/mduerst/papers/PDF/IUC11-UTF-8.pdf">
1808<front>
1809<title>The Properties and Promises of UTF-8</title>
1810  <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"></author>
1811<date year="1997" month="September"/>
1812</front>
1813<seriesInfo name="Proc. 11th International Unicode Conference, San Jose" value=""/>
1814</reference>
1815
1816<reference anchor="Gettys" target="http://www.w3.org/DesignIssues/ModelConsequences">
1817<front>
1818<title>URI Model Consequences</title>
1819<author initials="J." surname="Gettys" fullname="Jim Gettys"><organization/></author>
1820<date month="" year=""/>
1821</front>
1822</reference>
1823
1824<reference anchor='HTML4' target='http://www.w3.org/TR/1999/REC-html401'>
1825<front>
1826<title>HTML 4.01 Specification</title>
1827<author fullname='David Raggett' surname='Raggett' initials='D. '/>
1828<author fullname='Arnaud Le Hors' surname='Le Hors' initials='A. '/>
1829<author fullname='Ian Jacobs' surname='Jacobs' initials='I. '/>
1830<date year='1999' month='December' day='24'/>
1831</front>
1832<seriesInfo name='W3C Recommendation' value='REC-html401-19991224'/>
1833</reference>
1834&rfc2130;
1835&rfc2141;
1836&rfc2192;
1837&rfc2277;
1838&rfc2384;
1839&rfc2396;
1840&rfc2397;
1841&rfc2616;
1842&rfc2640;
1843
1844  <reference anchor="RFC3987">
1845    <front>
1846      <title>Internationalized Resource Identifiers (IRIs)</title>
1847      <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"/>
1848      <author initials="M." surname="Suignard" fullname="M. Suignard">
1849        <organization/>
1850      </author>
1851      <date year="2005" month="January"/>
1852    </front>
1853    <seriesInfo name="RFC" value="3987"/>
1854    <format type="TXT" octets="111190" target="http://www.rfc-editor.org/rfc/rfc3987.txt"/>
1855  </reference>
1856
1857&rfc5122;
1858&rfc6055;
1859
1860  <reference anchor="RFC6068">
1861    <front>
1862      <title>
1863        The 'mailto' URI Scheme
1864      </title>
1865      <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"/>
1866      <author initials="L." surname="Masinter" fullname="L. Masinter">
1867        <organization/>
1868      </author>
1869      <author initials="J." surname="Zawinski" fullname="J. Zawinski">
1870        <organization/>
1871      </author>
1872      <date year="2010" month="October"/>
1873    </front>
1874    <seriesInfo name="RFC" value="6068"/>
1875    <format type="TXT" octets="36683" target="http://www.rfc-editor.org/rfc/rfc6068.txt"/>
1876  </reference>
1877
1878<reference anchor='Bidi'>
1879  <front>
1880    <title>Guidelines for Internationalized Resource Identifiers with Bi-directional Characters (Bidi IRIs)</title>
1881    <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"/>
1882    <author initials='L.' surname='Masinter' />
1883    <author initials="A." isurname="Allawi (عادل علاوي)" surname="Allawi"
1884      ifullname="عادل علاوي" fullname="Adil Allawi"/>    <date year="2012" month="March" day="9" />
1885  </front>
1886  <seriesInfo name="Internet-Draft" value="draft-ietf-iri-bidi-guidelines-02"/>
1887</reference>
1888
1889<reference anchor='Equivalence'>
1890  <front>
1891    <title>Equivalence and Canonicalization of Internationalized Resource Identifiers (IRIs)</title>
1892    <author initials='L.' surname='Masinter' />
1893    <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"/>
1894    <date year="2012" month="March" day="2" />
1895  </front>
1896  <seriesInfo name="Internet-Draft" value="draft-ietf-iri-comparison-01"/>
1897</reference>
1898
1899<reference anchor='RFC4395bis'>
1900  <front>
1901    <title>Guidelines and Registration Procedures for New URI/IRI Schemes</title>
1902    <author initials='T.' surname='Hansen' fullname="Tony Hansen"><organization/></author>
1903    <author initials='T.' surname='Hardie' fullname="Ted Hardie"><organization/></author>
1904    <author initials='L.' surname='Masinter' fullname="Larry Masinter"><organization/></author>
1905    <date year='2011' month='December'/>
1906    <workgroup>IRI</workgroup>
1907  </front>
1908  <seriesInfo name="Internet-Draft" value="draft-ietf-iri-4395bis-irireg-04"/>
1909</reference>
1910 
1911 
1912<reference anchor="UNIXML" target="http://www.w3.org/TR/unicode-xml/">
1913<front>
1914<title>Unicode in XML and other Markup Languages</title>
1915  <author  initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst" fullname="Martin J. Duerst"><organization/></author>
1916<author initials="A." surname="Freytag" fullname="Asmus Freytag"><organization/></author>
1917<date year="2003" month="June" day="18"/>
1918</front>
1919<seriesInfo name="Unicode Technical Report" value="#20"/>
1920<seriesInfo name="World Wide Web Consortium" value="Note"/>
1921</reference>
1922 
1923<reference anchor="UTR36" target="http://unicode.org/reports/tr36/">
1924<front>
1925<title>Unicode Security Considerations</title>
1926<author initials="M." surname="Davis" fullname="Mark Davis"><organization/></author>
1927<author initials="M." surname="Suignard" fullname="Michel Suignard"><organization/></author>
1928<date year="2010" month="August" day="4"/>
1929</front>
1930<seriesInfo name="Unicode Technical Report" value="#36"/>
1931</reference>
1932
1933<reference anchor='XLink' target='http://www.w3.org/TR/xlink11/#link-locators'>
1934<front>
1935<title>XML Linking Language (XLink) Version 1.1</title>
1936<author fullname='Steve DeRose' surname='DeRose' initials='S. '/>
1937<author fullname='Eve Maler' surname='Maler' initials='E. '/>
1938<author fullname='David Orchard' surname='Orchard' initials='D. '/>
1939<author fullname='Norman Walsh' surname='Walsh' initials='N. '/>
1940<date year='2010' month='May' day='06'/>
1941</front>
1942<seriesInfo name='W3C Recommendation' value='REC-xlink11-20100506'/>
1943</reference>
1944 
1945<reference anchor='XML1' target='http://www.w3.org/TR/2008/REC-xml/'>
1946<front>
1947<title>Extensible Markup Language (XML) 1.0 (Fifth Edition)</title>
1948<author fullname='Tim Bray' surname='Bray' initials='T. '/>
1949<author fullname='Jean Paoli' surname='Paoli' initials='J. '/>
1950<author fullname='C. M. Sperberg-McQueen' surname='Sperberg-McQueen' initials='C. M. '/>
1951<author fullname='Eve Maler' surname='Maler' initials='E. '/>
1952<author initials="F." surname="Yergeau" ifullname="François Yergeau" fullname="Francois Yergeau"/>
1953<date year='2008' month='November' day='26'/>
1954</front>
1955<seriesInfo name='W3C Recommendation' value='REC-xml-20081126'/>
1956</reference>
1957 
1958<reference anchor="XMLSchema" target="http://www.w3.org/TR/xmlschema-2/#anyURI">
1959<front>
1960<title>XML Schema Part 2: Datatypes Second Edition</title>
1961<author fullname='Paul V. Biron' surname='Biron' initials='P. V. '/>
1962<author fullname='Ashok Malhotra' surname='Malhotra' initials='A. '/>
1963<date year='2004' month='October' day='28'/>
1964</front>
1965<seriesInfo name='W3C Recommendation' value='REC-xmlschema-2-20041028'/>
1966</reference>
1967 
1968<reference anchor="XPointer" target="http://www.w3.org/TR/xptr-framework/#escaping">
1969<front>
1970<title>XPointer Framework</title>
1971<author fullname='Paul Grosso' surname='Grosso' initials='P. '/>
1972<author fullname='Eve Maler' surname='Maler' initials='E. '/>
1973<author fullname='Jonathan Marsh' surname='Marsh' initials='J. '/>
1974<author fullname='Norman Walsh' surname='Walsh' initials='N. '/>
1975<date year='2003' month='March' day='25'/>
1976</front>
1977<seriesInfo name='W3C Recommendation' value='REC-xptr-framework-20030325'/>
1978</reference>
1979
1980</references>
1981
1982</back>
1983</rfc>
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