source: draft-ietf-iri-3987bis/draft-ietf-iri-bidi-guidelines.xml @ 140

Last change on this file since 140 was 140, checked in by duerst@…, 7 years ago

added warning about viewing bidi examples, and an test example that users can verify visually.

File size: 27.5 KB
Line 
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 rfc3490 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3490.xml">
5<!ENTITY rfc3987 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3987.xml">
6<!ENTITY DRAFT "draft-ietf-iri-bidi-guidelines-03">
7<!ENTITY YEAR "2012">
8]>
9<?rfc strict='yes'?>
10
11<?xml-stylesheet type='text/css' href='rfc2629.css' ?>
12<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
13<?rfc symrefs='yes'?>
14<?rfc sortrefs='yes'?>
15<?rfc iprnotified="no" ?>
16<?rfc toc='yes'?>
17<?rfc compact='yes'?>
18<?rfc subcompact='no'?>
19<rfc ipr="pre5378Trust200902" docName="&DRAFT;"
20  category="bcp" xml:lang="en">
21  <front>
22    <title abbrev="Bidi IRI Guidelines">Guidelines for Internationalized
23      Resource Identifiers with Bi-directional Characters (Bidi IRIs)</title>
24    <author initials="M.J." isurname="Dürst" surname="Duerst" ifullname="Martin J. Dürst"
25      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.)">
26      <organization>Aoyama Gakuin University<ionly> (青山学院大学)</ionly> </organization>
27      <address>
28        <postal>
29          <street>5-10-1 Fuchinobe</street>
30          <street>Chuo-ku</street>
31          <city>Sagamihara</city>
32          <region>Kanagawa</region>
33          <code>252-5258</code>
34          <country>Japan</country>
35        </postal>
36        <phone>+81 42 759 6329</phone>
37        <facsimile>+81 42 759 6495</facsimile>
38        <email>duerst@it.aoyama.ac.jp</email>
39        <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>
40      </address>
41    </author>
42    <author initials="L." surname="Masinter" fullname="Larry Masinter">
43      <organization>Adobe</organization>
44      <address>
45        <postal>
46          <street>345 Park Ave</street>
47          <city>San Jose</city>
48          <region>CA</region>
49          <code>95110</code>
50          <country>U.S.A.</country>
51        </postal>
52        <phone>+1-408-536-3024</phone>
53        <email>masinter@adobe.com</email>
54        <uri>http://larry.masinter.net</uri>
55      </address>
56    </author>
57    <author initials="A." isurname="Allawi (عادل علاوي)" surname="Allawi"
58      ifullname="Adil Allawi (عادل علاوي)" fullname="Adil Allawi">
59    <organization>Diwan Software Limited</organization>
60      <address>
61        <postal>
62          <street>37-39 Peckham Road</street>
63          <city>London</city>
64          <code>SE5 8UH</code>
65          <country>United Kingdom</country>
66        </postal>
67        <phone>+44 7718 785850</phone>
68        <facsimile>+44 20 72525444</facsimile>
69        <email>adil@diwan.com</email>
70        <uri>http://ironymark.diwan.com/</uri>
71      </address>
72    </author>
73    <date year="&YEAR;" month="October" />
74    <area>Applications</area>
75    <workgroup>Internationalized Resource Identifiers (iri)</workgroup>
76    <keyword>IRI</keyword>
77    <keyword>Internationalized Resource Identifier</keyword>
78    <keyword>BIDI</keyword>
79    <keyword>URI</keyword>
80    <keyword>URL</keyword>
81    <keyword>IDN</keyword>
82    <abstract>
83      <t>This specification gives guidelines for selection, use, and
84        presentation of International Resource Identifiers (IRIs) which include
85        characters with inherent right-to-left (rtl) writing direction. </t>
86    </abstract>
87  </front>
88  <middle>
89    <section title="Introduction">
90      <section title='Overview'>
91      <t>Some UCS characters, such as those used in the Arabic and Hebrew
92        scripts, have an inherent right-to-left (rtl) writing direction as
93        opposed to characters, such as those in the Latin script, that have an
94        inherent left-to-right (ltr) direction. IRIs containing rtl characters
95        (called bidirectional IRIs or Bidi IRIs) require additional attention
96        because of the non-trivial relation between their logical and visual
97        ordering. The logical order represents the order in which characters are
98        stored on computers and read by people. The visual order is the order in
99        which the characters appear (or are expected to appear) on a computer
100        display or printout.</t>
101      <t>Generally, alphabetic characters in scripts like Arabic and Hebrew are
102        drawn rtl while numbers are drawn ltr. Symbols such as slash ('/') and
103        period ('.') take their visual direction from the surrounding characters.</t>
104      <t>Because of this complex interaction between the logical representation,
105        the visual representation, and the syntax of a Bidi IRI, a balance is
106        needed between various requirements. The main requirements are: <list
107        style="hanging">
108        <t hangText="1.">user-predictable conversion between visual and logical
109          representation;</t>
110        <t hangText="2.">the ability to include a wide range of characters in
111          various parts of the IRI; and</t>
112        <t hangText="3.">minor or no changes or restrictions for
113          implementations.</t>
114        </list></t>
115        </section>
116      <section title='Availability'>
117        <t>This document is available in (line-printer ready) plaintext ASCII and in PDF.
118          It is also available in HTML from
119          <vspace/><eref target="http://www.sw.it.aoyama.ac.jp/&YEAR;/pub/&DRAFT;.html"
120            >http://www.sw.it.aoyama.ac.jp/&YEAR;/pub/&DRAFT;.html</eref>,
121          and in UTF-8 plaintext from
122          <vspace/><eref target="http://www.sw.it.aoyama.ac.jp/&YEAR;/pub/&DRAFT;.utf8.txt"
123            >http://www.sw.it.aoyama.ac.jp/&YEAR;/pub/&DRAFT;.utf8.txt</eref>.
124          While all these versions are identical in their technical content,
125          the HTML, PDF, and UTF-8 plaintext versions show non-Unicode characters directly.
126          This often makes it easier to understand examples, and readers are therefore strongly advised
127          to consult these versions in preference or as a supplement to the ASCII version.</t>
128        <t>This document contains bidirectional examples. In order to correctly understand
129           the examples, it is important to view this document with a tool that
130           correctly implements the Unicode Bidirectional Algorithm <xref target="UNI9"/>.
131           Most many text viewers and text editors, and most browsers, currently implement
132           the Unicode Bidirectional Algorithm, but there are some exceptions.
133           In order to check whether a tool implements the Unicode Bidirectional Algorithm,
134            please observe the line of Hebrew characters below:</t>
135           <t><span dir='ltr'>א, אב, אבג, אבגד ,אבגדה, אבגדהו</span><t/>
136           <t>If the shortest word (one letter) is on the right, and the longest word (six characters)
137           is on the left, and the words get longer and longer from right to left,
138           and the commas are between the words, but on the right of the spaces,
139           then your tool should be okay. Otherwise, please use another tool.
140           Please note that the example is only in Hebrew because in Arabic,
141           it is difficult to count characters for people who are not familiar
142           with the script.</t>
143      </section>
144      <section title="Notation">
145        <t>In this document, "Bidi Notation", abbreviated "BN" is used for the given Bidi IRI
146          examples as follows: Lower case letters a-z stand for characters that
147          are written with a left to right ordering (such as Latin characters),
148          whereas upper case letters A-Z represent characters that are written
149          right to left (such as Arabic or Hebrew characters). Numbers and
150          symbols are the same.</t>
151        <t> In this document, the key words "MUST", "MUST NOT", "REQUIRED",
152          "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
153          and "OPTIONAL" are to be interpreted as described in <xref
154            target="RFC2119"/>.</t>
155      </section>
156      <!-- Notation -->
157    </section>
158    <!-- Introduction -->
159    <section title="Logical Storage and Visual Presentation" anchor="visual">
160      <t>When stored or transmitted in digital representation, Bidi IRIs MUST be
161        in full logical order and MUST conform to the IRI syntax rules (which
162        includes the rules relevant to their scheme). This ensures that
163        Bidi IRIs can be processed in the same way as other IRIs.</t>
164      <t>Bidi IRIs MUST be visually ordered by the Unicode Bidirectional
165        Algorithm <xref target="UNIV6"/>, <xref target="UNI9"/>. Bidi IRIs MUST
166        be rendered in the same way as they would be if they were in a
167        left-to-right embedding. </t>
168      <t>In conformance with the Unicode Bidirectional Algorithm, embedding MAY
169        be done in one of two ways: <list style="hanging">
170        <t hangText="1.">precede the IRI with U+202A, LEFT-TO-RIGHT EMBEDDING
171          (LRE), and follow with U+202C, POP DIRECTIONAL FORMATTING (PDF);
172          or</t>
173        <t hangText="2.">use a higher-level protocol (e.g., the dir='ltr'
174          attribute in HTML).</t>
175        </list></t>
176      <t>Preceding and following the Bidi IRI with U+200E, LEFT-TO-RIGHT MARK
177        (LRM). Is NOT RECOMMENDED as, there are cases where this may not be
178        sufficient to match full left to right embedding.</t>
179      <t>There is no requirement to use embedding if the display is still the
180        same without the embedding. For example, a Bidi IRI in a text
181        with left-to-right base directionality (such as used for English or
182        Cyrillic) that is preceded and followed by whitespace and strong
183        left-to-right characters does not need an embedding. Also, a
184        bidirectional relative IRI reference that only contains strong
185        right-to-left characters and weak characters (such as symbols) and that
186        starts and ends with a strong right-to-left character and appears in a
187        text with right-to-left base directionality (such as used for Arabic or
188        Hebrew) and is preceded and followed by whitespace and strong characters
189        does not need an embedding.</t>
190      <t>However, Implementers are, RECOMMENDED to use embedding in all cases
191        where they are not completely sure that the display behavior is
192        unaffected without the embedding.</t>
193      <t>The Unicode Bidirectional Algorithm (<xref target="UNI9"/>, section
194        4.3) permits higher-level protocols to influence bidirectional
195        rendering. Such changes by higher-level protocols MUST NOT be used if
196        they change the rendering of IRIs.</t>
197      <t>The bidirectional formatting characters that may be used before or
198        after the IRI to ensure correct display are not themselves part of the
199        IRI. IRIs MUST NOT contain bidirectional formatting characters (LRM,
200        RLM, LRE, RLE, LRO, RLO, and PDF). They affect the visual rendering of
201        the IRI but do not appear themselves. It would therefore not be possible
202        to input an IRI with such characters correctly.</t>
203    </section>
204    <!-- visual -->
205    <section title="Bidi IRI Structure" anchor="bidi-structure">
206      <t>The Unicode Bidirectional Algorithm is designed for general purpose
207        text. To make sure that it does not affect the rendering of Bidi IRIs
208        outside of the requirements of this document, some restrictions on Bidi
209        IRIs are necessary. These restrictions are given in terms of delimiters
210        (structural characters, mostly punctuation such as "@", ".", ":", and
211        "/") and components (usually consisting mostly of letters and
212        digits).</t>
213      <t>The following syntax rules from the ABNF of <xref target="RFC3987bis"/>
214        correspond to components for the purpose of Bidi behavior: iuserinfo,
215        ireg-name, isegment, isegment-nz, isegment-nz-nc, ireg-name, iquery, and
216        ifragment.</t>
217      <t>Specifications that define the syntax of any of the above components
218        MAY divide them further and define smaller parts to be components
219        according to this document. As an example, the restrictions of <xref
220          target="RFC3490"/> on bidirectional domain names correspond to treating
221        each label of a domain name as a component for schemes with ireg-name as
222        a domain name. Even where the components are not defined formally, it
223        may be helpful to think about some syntax in terms of components and to
224        apply the relevant restrictions. For example, for the usual name/value
225        syntax in query parts, it is convenient to treat each name and each
226        value as a component. As another example, the extensions in a resource
227        name can be treated as separate components.</t>
228      <t>For each component, the following restrictions apply:</t>
229      <t> <list style="hanging">
230        <t hangText="1.">A component SHOULD NOT use both right-to-left and
231          left-to-right characters.</t>
232        <t hangText="2.">A component using right-to-left characters SHOULD start
233          and end with right-to-left characters.</t>
234      </list></t>
235      <t>The above restrictions are given as "SHOULD"s, rather than as "MUST"s.
236        For IRIs that are never presented visually, they are not relevant.
237        However, for IRIs in general, they are very important to ensure
238        consistent conversion between visual presentation and logical
239        representation, in both directions.</t>
240      <t><list style="hanging">
241        <t hangText="Note:">In some components, the above restrictions may
242          actually be strictly enforced. For example, <xref target="RFC3490"/>
243          requires that these restrictions apply to the labels of a host name
244          for those schemes where ireg-name is a host name. In some other
245          components (for example, path components) following these restrictions
246          may not be too difficult. For other components, such as parts of the
247          query part, it may be very difficult to enforce the restrictions
248          because the values of query parameters may be arbitrary character
249          sequences.</t>
250      </list></t>
251      <t>If the above restrictions cannot be satisfied otherwise, the affected
252        component can always be mapped to URI notation using the general
253        percent-encoding of IRI components, as described in <xref
254          target="RFC3987bis"/>. Please note that the whole component has to be
255        mapped (see also Example 9 below).</t>
256    </section>
257    <!-- bidi-structure -->
258    <section title="Input of Bidi IRIs" anchor="bidiInput">
259      <t>Bidi input methods MUST generate Bidi IRIs in logical order while
260        rendering them according to <xref target="visual"/>. During input,
261        rendering SHOULD be updated after every new character is input to avoid
262        end-user confusion.</t>
263    </section>
264    <!-- bidiInput -->
265    <section title="Examples">
266      <t>This section gives examples of Bidi IRIs in Bidi Notation. It shows
267        legal IRIs with the relationship between their logical and visual
268        representation and explains how certain phenomena in this relationship
269        may look strange to somebody not familiar with bidirectional behavior,
270        but familiar to users of Arabic and Hebrew. It also shows what happens
271        if the restrictions given in <xref target="bidi-structure"/> are not
272        followed. The examples below can be seen at <xref target="BidiEx"/>, in
273        Arabic, Hebrew, and Bidi Notation variants.</t>
274      <t>To read the bidi text in the examples, read the visual representation
275        from left to right until you encounter a block of rtl text. Read the rtl
276        block (including slashes and other special characters) from right to
277        left, then continue at the next unread ltr character.</t>
278      <t>Please note that "BN" stands for "Bidi Notation", see <eref target="Notation" />.
279        AR stands for Arabic, HE for Hebrew.</t>
280
281      <t>Example 1: A single component with rtl characters is inverted:
282
283        <vspace/>Logical representation (BN): "http://ab.CDEFGH.ij/kl/mn/op.html"
284        <vspace/>Visual representation (BN): "http://ab.HGFEDC.ij/kl/mn/op.html"
285        <ionly>
286        <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.تثجحخد.ij/kl/mn/op.html</span>"
287        <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.גדהוזח.ij/kl/mn/op.html</span>"
288        </ionly>
289        <vspace/>Components can be read one
290        by one, and each component can be read in its natural direction.</t>
291
292      <t>Example 2: More than one consecutive component with rtl characters is
293        inverted as a whole:
294
295        <vspace/>Logical representation (BN): "http://ab.CDE.FGH/ij/kl/mn/op.html"
296        <vspace/>Visual representation (BN): "http://ab.HGF.EDC/ij/kl/mn/op.html"
297        <ionly>
298          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.تثج.حخد/ij/kl/mn/op.html</span>"
299          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.גדה.וזח/ij/kl/mn/op.html</span>"
300        </ionly>
301       
302        <vspace/> A sequence of rtl
303        components is read rtl, in the same way as a sequence of rtl words is
304        read rtl in a bidi text.</t>
305
306      <t>Example 3: All components of an IRI (except for the scheme) are rtl.
307        All rtl components are inverted overall:
308
309        <vspace/>Logical representation (BN): "http://AB.CD.EF/GH/IJ/KL?MN=OP;QR=ST#UV"
310        <vspace/>Visual representation (BN): "http://VU#TS=RQ;PO=NM?LK/JI/HG/FE.DC.BA"
311        <ionly>
312          <vspace/>Visual representation (AR): "<span dir='ltr'>http://اب.تث.جح/خد/ذر/زس?شص=ضط;ظع=غف#قك</span>"
313          <vspace/>Visual representation (HE): "<span dir='ltr'>http://אב.גד.הו/זח/טי/כל?מן=סע;פץ=קר#שת</span>"
314        </ionly>
315       
316        <vspace/> The
317        whole IRI (except the scheme) is read rtl. Delimiters between rtl
318        components stay between the respective components; delimiters between
319        ltr and rtl components don't move.</t>
320
321      <t>Example 4: Each of several sequences of rtl components is inverted on
322        its own:
323
324        <vspace/>Logical representation (BN): "http://AB.CD.ef/gh/IJ/KL.html"
325        <vspace/>Visual representation (BN): "http://DC.BA.ef/gh/LK/JI.html"
326        <ionly>
327          <vspace/>Visual representation (AR): "<span dir='ltr'>http://اب.تث.ef/gh/ذر/زس.html</span>"
328          <vspace/>Visual representation (HE): "<span dir='ltr'>http://אב.גד.ef/gh/טי/כל.html</span>"
329        </ionly>
330       
331        <vspace/> Each sequence of rtl components
332        is read rtl, in the same way as each sequence of rtl words in an ltr
333        text is read rtl.</t>
334
335      <t>Example 5: Example 2, applied to components of different kinds:
336
337        <vspace/>Logical representation (BN): "http://ab.cd.EF/GH/ij/kl.html"
338        <vspace/>Visual representation (BN): "http://ab.cd.HG/FE/ij/kl.html"
339        <ionly>
340          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.cd.جح/خد/ij/kl.html</span>"
341          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.cd.הו/זח/ij/kl.html</span>"
342        </ionly>
343       
344        <vspace/>
345        The inversion of the domain name label and the path component may be
346        unexpected, but it is consistent with other bidi behavior. For
347        reassurance that the domain component really is "ab.cd.EF", it may be
348        helpful to read aloud the visual representation following the Unicode
349        Bidirectional Algorithm. After "http://ab.cd." one reads the RTL block
350        "E-F-slash-G-H", which corresponds to the logical representation. </t>
351
352      <t>Example 6: Same as Example 5, with more rtl components:
353       
354        <vspace/>Logical representation (BN): "http://ab.CD.EF/GH/IJ/kl.html"
355        <vspace/>Visual representation (BN): "http://ab.JI/HG/FE.DC/kl.html"
356        <ionly>
357          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.تث.جح/خد/ذر/kl.html</span>"
358          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.גד.הו/זח/טי/kl.html</span>"
359        </ionly>
360       
361        <vspace/> The inversion of the domain
362        name labels and the path components may be easier to identify because
363        the delimiters also move.</t>
364     
365      <t>Example 7: A single rtl component includes digits:
366
367        <vspace/>Logical representation (BN): "http://ab.CDE123FGH.ij/kl/mn/op.html"
368        <vspace/>Visual representation (BN): "http://ab.HGF123EDC.ij/kl/mn/op.html"
369        <ionly>
370          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.تثج123حخد.ij/kl/mn/op.html</span>"
371          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.גדה123וזח.ij/kl/mn/op.html</span>"
372        </ionly>
373       
374        <vspace/> Numbers
375        are written ltr in all cases but are treated as an additional embedding
376        inside a run of rtl characters. This is completely consistent with usual
377        bidirectional text.</t>
378
379      <t>Example 8 (not allowed): Numbers are at the start or end of an rtl
380        component:
381       
382        <vspace/>Logical representation (BN): "http://ab.cd.ef/GH1/2IJ/KL.html"
383        <vspace/>Visual representation (BN): "http://ab.cd.ef/LK/JI1/2HG.html"
384        <ionly>
385          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.cd.ef/خد1/2ذر/زس.html</span>"
386          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.cd.ef/זח1/2טי/כל.html</span>"
387        </ionly>
388       
389        <vspace/> The sequence "1/2" is
390        interpreted by the Bidirectional Algorithm as a fraction, fragmenting the
391        components and leading to confusion. There are other characters that are
392        interpreted in a special way close to numbers; in particular, "+", "-",
393        "#", "$", "%", ",", ".", and ":".</t>
394
395      <t>Example 9 (not allowed): The numbers in the previous example are
396        percent-encoded:
397       
398        <vspace/>Logical representation (BN): "http://ab.cd.ef/GH%31/%32IJ/KL.html"
399        <vspace/>Visual representation (BN): "http://ab.cd.ef/LK/JI%32/%31HG.html"
400        <ionly>
401          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.cd.ef/זח%31/%32טי/כל.html</span>"
402          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.cd.ef/خد%31/%32ذر/زس.html</span>"
403        </ionly>
404       
405      </t>
406     
407      <t>Example 10 (allowed but not recommended):
408       
409        <vspace/>Logical representation (BN): "http://ab.CDEFGH.123/kl/mn/op.html"
410        <vspace/>Visual representation (BN): "http://ab.123.HGFEDC/kl/mn/op.html"
411        <ionly>
412          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.تثجحخد.123/kl/mn/op.html</span>"
413          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.גדהוזח.123/kl/mn/op.html</span>"
414        </ionly>
415       
416        <vspace/> Components
417        consisting of only numbers are allowed (it would be rather difficult to
418        prohibit them), but these may interact with adjacent RTL components in
419        ways that are not easy to predict.</t>
420
421      <t>Example 11 (allowed but not recommended):
422       
423        <vspace/>Logical representation (BN): "http://ab.CDEFGH.123ij/kl/mn/op.html"
424        <vspace/>Visual representation (BN): "http://ab.123.HGFEDCij/kl/mn/op.html"
425        <ionly>
426          <vspace/>Visual representation (AR): "<span dir='ltr'>http://ab.تثجحخد.123ij/kl/mn/op.html</span>"
427          <vspace/>Visual representation (HE): "<span dir='ltr'>http://ab.גדהוזח.123ij/kl/mn/op.html</span>"
428        </ionly>
429       
430        <vspace/>
431        Components consisting of numbers and left-to-right characters are
432        allowed, but these may interact with adjacent RTL components in ways
433        that are not easy to predict.</t>
434    </section>
435    <!-- examples -->
436    <section title="IANA Considerations" anchor="iana">
437      <t>This document makes no changes to IANA registries.</t>
438    </section>
439    <!-- IANA -->
440    <section title="Security Considerations" anchor="security">
441      <t>Confusion can occur with bidirectional IRIs, if the restrictions in
442        <xref target="bidi-structure"/> are not followed. The same visual
443        representation may be interpreted as different logical representations,
444        and vice versa. It is also very important that a correct Unicode
445        bidirectional implementation be used.</t>
446    </section>
447    <!-- security -->
448    <section title="Acknowledgements">
449      <t>This document was derived from <xref target="RFC3987"/> and <xref
450        target="RFC3987bis"/> and the acknowledgments of those documents
451        apply.</t>
452    </section>
453    <!-- acknowledgements -->
454    <section title="Main Changes Since RFC 3987">
455      <t>This section describes the main changes since <xref target="RFC3987"></xref>.</t>       
456        <t>Note to RFC Editor: Please remove this paragraph before publication.
457          Detailled change logs are available in the IETF tools subversion repository at
458          http://trac.tools.ietf.org/wg/iri/trac/log/draft-ietf-iri-3987bis/draft-ietf-iri-bidi-guidelines.xml.</t>
459       
460      <t><list style="symbols">
461        <t>Separated out the section on bidi in <xref target="RFC3987"/> to this document.</t>
462        <t>Added examples in Arabic and Hebrew, which can be seen in html/pdf/utf8.txt versions.</t>
463        <t>TODO: check for major changes between RFC3987 and draft -02.</t>
464      </list>
465      </t>
466    </section>
467  </middle>
468  <back>
469    <references title="Normative References">
470      <reference anchor="RFC3987bis"
471        target="http://tools.ietf.org/id/draft-ietf-iri-3987bis">
472        <front>
473          <title>Internationalized Resource Identifiers (IRIs)</title>
474          <author initials="M." surname="Duerst"/>
475          <author initials="L." surname="Masinter" fullname="Larry Masinter"/>
476          <author initials="M." surname="Suignard"/>
477          <date year="2011" month="August" day="14"/>
478        </front>
479      </reference>
480      &rfc2119;
481      &rfc3490;
482      <reference anchor="UNIV6">
483        <front>
484          <title>The Unicode Standard, Version 6.0.0 (Mountain View, CA, The
485            Unicode Consortium, 2011, ISBN 978-1-936213-01-6)</title>
486          <author>
487            <organization>The Unicode Consortium</organization>
488          </author>
489          <date year="2010" month="October"/>
490        </front>
491      </reference>
492      <reference anchor="UNI9"
493        target="http://www.unicode.org/reports/tr9/tr9-13.html">
494        <front>
495          <title>The Unicode Bidirectional Algorithm</title>
496          <author initials="M." surname="Davis" fullname="Mark Davis">
497            <organization/>
498          </author>
499          <date year="2004" month="March"/>
500        </front>
501        <seriesInfo name="Unicode Standard Annex" value="#9"/>
502      </reference>
503    </references>
504    <references title="Informative References">
505      <reference anchor="BidiEx"
506        target="http://www.w3.org/International/iri-edit/BidiExamples">
507        <front>
508          <title>Examples of Bidi IRIs</title>
509          <author>
510            <organization/>
511          </author>
512          <date year="" month=""/>
513        </front>
514      </reference> &rfc3987; </references>
515  </back>
516</rfc>
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