One document matched: draft-ietf-idnabis-bidi-01.txt
Differences from draft-ietf-idnabis-bidi-00.txt
Network Working Group H. Alvestrand, Ed.
Internet-Draft Google
Intended status: Standards Track C. Karp, Ed.
Expires: January 7, 2009 Swedish Museum of Natural History
July 6, 2008
An updated IDNA criterion for right-to-left scripts
draft-ietf-idnabis-bidi-01
Status of this Memo
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Abstract
The use of right-to-left scripts in internationalized domain names
has presented several challenges. This memo discusses some problems
with these scripts, and some shortcomings in the 2003 IDNA BIDI
criterion. Based on this discussion, it proposes a new BIDI
criterion for IDNA labels.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Purpose and applicability . . . . . . . . . . . . . . . . 3
1.2. Background and history . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Detailed examples . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Dhivehi . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Yiddish . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Strings with numbers . . . . . . . . . . . . . . . . . . . 7
3. An expanded justification for the BIDI rule . . . . . . . . . 7
4. A replacement for the RFC 3454 rule . . . . . . . . . . . . . 10
5. Other issues in need of resolution . . . . . . . . . . . . . . 12
6. Compatibility considerations . . . . . . . . . . . . . . . . . 12
6.1. Backwards compatibility considerations . . . . . . . . . . 12
6.2. Forward compatibiltiy considerations . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative references . . . . . . . . . . . . . . . . . . . 15
10.2. Informative references . . . . . . . . . . . . . . . . . . 15
Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 15
A.1. Changes from draft-alvestrand-00 to -01 . . . . . . . . . 15
A.2. Changes from -01 to -02 . . . . . . . . . . . . . . . . . 15
A.3. Changes from -02 to -03 . . . . . . . . . . . . . . . . . 15
A.4. Changes from -03 to -04 . . . . . . . . . . . . . . . . . 16
A.5. Changes from draft-alvestrand-04 to draft-ietf -00 . . . . 16
A.6. Changes from idnabis -00 to -01 . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
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1. Introduction
1.1. Purpose and applicability
This document's purpose is to establish a test that can be applied to
Internationalized Domain Name (IDN) labels in Unicode form (U-labels)
containing right-to-left characters.
When labels pass the test, they can be used with a minimal chance of
these labels being displayed in a confusing way by a bidirectional
display algorithm. In order to achieve this stability, it is also
necessary that the test be applied to labels occurring before or
after the label containing right-to-left characters, which prohibits
some LDH-labels that are permitted in other contexts.
[[NOTE IN DRAFT: Verify whether it is enough to place requirements on
the following label, if the label with RTL characters doesn't start
with a digit.]]
This specification does not place any requirements on domain names
that do not contain right-to-left characters.
1.2. Background and history
The IDNA specification "Stringprep", [RFC3454] makes the following
statement in its section 6 on the BIDI algorithm, :
3) If a string contains any RandALCat character, a RandALCat
character MUST be the first character of the string, and a
RandALCat character MUST be the last character of the string.
(A RandALCat character is a character with unambiguously right-to-
left directionality.)
The reasoning behind this prohibition was to ensure that every
component of a displayed domain name has an unambiguously preferred
direction. However, this makes certain words in languages written
with right-to-left scripts invalid as IDN labels, and in at least one
case means that all the words of an entire language are forbidden as
IDN labels.
This will be illustrated below with examples taken from the Dhivehi
and Yiddish languages, as written with the Thaana and Hebrew scripts,
respectively.
In investigating this problem, it was realized that the RFC 3454
specification did not exactly specify what the requirement to be
fulfilled was, and therefore, it was impossible to tell whether a
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simple relaxation of the rule would continue to fulfil the
requirement. A further investigation led to the conclusion that for
one reasonable set of requirements, IDNA2003's BIDI restriction did
not fulfil the requirements. This document therefore proposes
replacing the RFC 3454 BIDI requirement in its entirety.
While the document proposes completely new text, most reasonable
labels that were allowed under the old criterion will also be allowed
under the new criterion, so the operational impact of the rule change
is limited.
1.3. Terminology
In this memo, we use "network order" to describe the sequence of
characters as transmitted on the wire or stored in a file; the terms
"first", "next", "previous", "before" and "after" are used to refer
to the relationship of characters and labels in network order.
We use "display order" to talk about the sequence of characters as
imaged on a display medium; the terms "left" and "right" are used to
refer to the relationship of characters and labels in display order.
Most of the time, the examples use the abbreviations for the Unicode
BIDI classes to denote the directionality of the characters; in some
examples, the convention that uppercase characters are of class R or
AL, and lowercase characters are of class L is used - thus, the
example string ABC.abc would consist of 3 right-to-left characters
and 3 left-to-right characters.
The other terminology used to describe IDNA concepts is defined in
[I-D.ietf-idnabis-rationale]
2. Detailed examples
2.1. Dhivehi
Dhivehi, the official language of the Maldives, is written with the
Thaana script. This displays some of the characteristics of Arabic
script, including its directional properties, and the indication of
vowels by the diacritical marking of consonantal base characters.
This marking is obligatory, and both double vowels and syllable-final
consonants are indicated by the marking of special unvoiced
characters. Every Dhivehi word therefore ends with a combining mark.
The word for "computer", which is romanized as "konpeetaru", is
written with the following sequence of Unicode code points:
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U+0786 THAANA LETTER KAAFU (AL)
U+07AE THAANA OBOFILI (NSM)
U+0782 THAANA LETTER NOONU (AL)
U+07B0 THAANA SUKUN (NSM)
U+0795 THAANA LETTER PAVIYANI (AL)
U+07A9 THAANA LETTER EEBEEFILI (AL)
U+0793 THAANA LETTER TAVIYANI (AL)
U+07A6 THAANA ABAFILI (NSM)
U+0783 THAANA LETTER RAA (AL)
U+07AA THAANA UBIUFILI (NSM)
The directionality class of U+07AA in the Unicode database is NSM
(non-spacing mark), which is not R or AL; a conformant implementation
of the IDNA2003 algorithm will say that "this is not in RandALCat",
and refuse to encode the string.
2.2. Yiddish
Yiddish is one of several languages written with the Hebrew script
(others include Hebrew and Ladino). This is basically a consonantal
alphabet (also termed an "abjad") but Yiddish is written using an
extended form that is fully vocalic. The vowels are indicated in
several ways, of which one is by repurposing letters that are
consonants in Hebrew. Other letters are used both as vowels and
consonants, with combining marks, called "points", used to
differentiate between them. Finally, some base characters can
indicate several different vowels, which are also disambiguated by
combining marks. Pointed characters can appear in word-final
position and may therefore also be needed at the end of labels. This
is not an invariable attribute of a Yiddish string and there is thus
greater latitude here than there is with Dhivehi.
The organization now known as the "YIVO Institute for Jewish
Research" developed orthographic rules for modern Standard Yiddish
during the 1930s on the basis of work conducted in several venues
since earlier in that century. These are given in, "The Standardized
Yiddish Orthography: Rules of Yiddish Spelling, 6th ed., YIVO
Institute for Jewish Research, New York, 1999, ISBN 0-914512-25-0",
("SYO") and are taken as normatively descriptive of modern Standard
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Yiddish in any context where that notion is deemed relevant. They
have been applied exclusively in all Yiddish dictionaries published
since their establishment, and are similarly dominant in academic and
bibliographic regards.
It therefore appears appropriate for this repertoire also to be
supported fully by IDNA. This presents no difficulty with characters
in initial and medial positions, but pointed characters are regularly
used in final position as well. All of the characters in the SYO
repertoire appear in both marked and unmarked form with one
exception: the HEBREW LETTER PE (U+05E4). The SYO only permits this
with a HEBREW POINT DAGESH (U+05BC), providing the Yiddish equivalent
to the Latin letter "p", or a HEBREW POINT RAFE (U+05BF), equivalent
to the Latin letter "f". There is, however, a separate unpointed
allograph, the HEBREW LETTER FINAL PE (U+05E3), for the latter
character when it appears in final position. The constraint on the
use of the SYO repertoire resulting from the proscription of
combining marks at the end of RTL strings thus reduces to nothing
more, or less, than the equivalent of saying that a string of Latin
characters cannot end with the letter "p". It must also be noted
that the HEBREW LETTER PE with HEBREW POINT DAGESH is characteristic
of almost all traditional Yiddish orthographies that predate (or
remain in use in parallel to) the SYO, being the first pointed
character to appear in any of them.
A more general instantiation of the basic problem can be seen in the
representation of the YIVO acronym. This is written with the Hebrew
letters YOD YOD HIRIQ VAV VAV ALEF QAMATS, where HIRIQ and QAMATS are
combining points:
U+05D9 HEBREW LETTER YOD (R)
U+05B4 HEBREW POINT HIRIQ (NSM)
U+05D5 HEBREW LETTER VAV (R)
U+05D0 HEBREW LETTER ALEF (R)
U+05B8 HEBREW POINT QAMATS (NSM)
The directionality class of U+05B8 HEBREW POINT QAMATS in the Unicode
database is NSM, which again causes the IDNA2003 algorithm to reject
the string.
It may also be noted that all of the combined characters mentioned
above exist in precomposed form at separate positions in the Unicode
chart. However, by invoking Stringprep, the IDNA2003 algorithm also
rejects those codepoints, for reasons not discussed here.
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2.3. Strings with numbers
RFC 3454, in its insistence that the first or last character of a
string be category R or AL, prohibited strings that contained right-
to-left characters and numbers at the end.
Consider the strings ALEF 5 (HEBREW LETTER ALEF + DIGIT FIVE) and 5
ALEF. Displayed in a LTR context, the first one will be displayed
from left to right as 5 ALEF (with the 5 being considered right-to-
left because of the leading ALEF), while 5 ALEF will be displayed in
exactly the same order (5 taking the direction from context).
Clearly, only one of those should be permitted as a registered label.
3. An expanded justification for the BIDI rule
One issue with RFC 3454 was that it did not give an explicit
justification for the BIDI rule, thus it was hard to tell if a
modified rule would continue to fulfil the purpose for which the RFC
3454 rule was written.
This document proposes an explicit justification, by stating a set of
requirements for which it is possible to test whether or not the
modified rule fulfils the requirement.
All the text in this document assumes that text containing the labels
under consideration will be displayed using the Unicode bidirectional
algorithm [UAX9].
The requirements proposed are these:
o Label Uniqueness: No two labels, when presented in display order
in the same paragraph, should have the same sequence of characters
without also having the same sequence of characters in network
order. (This is the criterion that is explicit in RFC 3454).
o Character Grouping: In a display of a string of labels, the
characters of each label should remain grouped between the
characters delimiting the labels.
o These requirements should be satisfied both when the string is
embedded in a paragraph with LTR direction and when it's embedded
in a paragraph with RTL direction. [[NOTE IN DRAFT: The need for
this requirement has been challenged. Should be decided by WG.]]
Several stronger statements were considered and rejected, because
they seem to be impossible to fulfil within the constraints of the
Unicode bidirectional algorithm. These include:
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o The appearance of a label should be unaffected by its embedding
context. This proved impossible even for ASCII labels; the label
"123-456" will have a different display order in an RTL context
than in a LTR context.
o The sequence of labels should be consistent with network order.
This proved impossible - a domain name consisting of the labels
(in network order) L1.R1.R2.L2 will be displayed as L1.R2.R1.L2 in
an LTR context.
o The Label Uniqueness property should hold true between LTR
paragraphs and RTL paragraphs. This was shown to be unsound.
o No two domain names should be displayed the same, even under
differing directionality. This was shown to be unsound, since the
domain name (network) ABC.abc will have display order CBA.abc in
an LTR context and abc.CBA in an RTL context, while the domain
name (network) abc.ABC will have display order abc.CBA in an LTR
context and CBA.abc in an RTL context.
One specific requirement was thought to be problematic, but turned
out to be satisfied by a string that obeys the proposed rules:
o The Character Grouping requirement should be satisfied when
directional controls (LRE, RLE, RLO, LRO, PDF) are used in the
same paragraph (outside of the labels). Because these controls
affect presentation order in non-obvious ways, by affecting the
"sor" and "eor" properties of the Unicode BIDI algorithm, the
conditions above would be very hard to satisfy for an useful set
of strings if this was true. As long as these controls have no
influence over the display of the domain name, no problem will be
caused, but the exact criterion for "will not influence" is hard
to codify.
For reference, here are the values that the Unicode BIDI property can
have:
o L - Left-to-right - most letters in LTR scripts
o R - Right-to-left - most letters in non-Arabic RTL scripts
o AL - Arabic letters - most letters in the Arabic script
o EN - European Number (0-9, and Extended Arabic-Indic numbers)
o ES - European Number Separator (+ and -)
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o ET - European Number Terminator (currency symbols, the hash sign,
the percent sign and so on)
o AN - Arabic Number
o CS - Common Number Separator (. , / : et al)
o NSM - Non spacing Mark - most combining accents
o BN - Boundary Neutral - control characters
o B - Paragraph Separator
o S - Segment Separator
o WS - Whitespace, including the SPACE character
o ON - Other Neutrals, including @, &, parentheses, MIDDLE DOT
o LRE, LRO, RLE, RLO, PDF - these are "directional control
characters", and are not used in IDNA labels.
In the following descriptions, first-level bullets are used to
indicate rules or normative statements; second-level bullets are
commentary.
The Character Grouping requirement can be more formally stated as:
o Let "Delimiterchars" be a set of characters with the Unicode BIDI
properties CS, WS, ON. (These are commonly used to delimit labels
- both the FULL STOP and the space are included.)
* ET, though it commonly occurs next to domain names in practice,
is problematic: the context R CS L EN ET (for instance A.a1%)
makes the label L EN not satisfy the character grouping
requirement.
* ES commonly occurs in labels as HYPHEN-MINUS, but could also be
used as a delimiter (for instance, the plus sign). It is left
out here.
A label L satisfies the Character Grouping requirement when, for any
Delimiter Character D1 and D2, and for any legal label S1 and S2
(which may have length zero):
If the string formed by concatenating S1, D1, L, D2 and S2 is
reordered according to the BIDI algorithm, then all the characters of
L in the reordered string are between D1 and D2, and no other
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characters are between D1 and D2, both if the overall paragraph
direction is LTR and if the overall paragraph direction is RTL.
Note that the definition is self-referential, since S1 and S2 are
constrained to be "legal" by this definition; this makes testing
changes to proposed rules a little complex, but does not create
problems for testing whether or not a given proposed rule satisfies
the criterion.
In a paragraph with an embedded string formed from the substrings A B
L C D, where A and D are (possibly zero-length) legal labels, and B
and C are single "Delimiter chars", the label L satisfies the
requirement if, for all A, B, C and D, the BIDI position of all
characters in L is within the range of positions for the characters
of L in the string, and the BIDI position of B and C is on opposite
sides of the string, for both the LTR and RTL paragraph direction.
(The "zero-length" case represents the case where a domain name is
next to something that isn't a domain name, separated by a delimiter
character).
The Label Uniqueness requirement can be formally stated as:
If two labels L and L', embedded as for the test above, displayed in
paragraphs with the same directionality, are reordered by the BIDI
algorithm into the same sequence of codepoints, at most one of the
labels L and L' is a legal label.
4. A replacement for the RFC 3454 rule
Based on the above discussion, and on testing, the following rule has
been developed for BIDI domain names:
A label containing a character of type R, AL or AN MUST satisfy the
criterion below. In addition, any label in a domain name immediately
after a label containing a character of type R, AL or AN MUST satisfy
the same criterion.
The main bullets give the rule, subordinate bullets (if any) give
justifications or examples of things that break if this rule is not
present.
Exhaustive testing has verified that all strings that satisfy this
criterion satisfy both the requirements above at least for all
strings up to 6 characters.
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1. Only characters with the BIDI properties L, R, AL, AN, EN, ES,
BN, ON and NSM are allowed.
* B, S and WS are excluded because they are separators or
spaces.
* LRE, LRO, RLE, RLO, PDF are excluded because they are BIDI
controls.
* ET is excluded because the string L ET does not satisfy the
Character Grouping requirement.
* CS is excluded because the string L CS does not satisfy the
Character Grouping requirement.
2. ES and ON are not allowed in the first position
* ES R and ON R do not satisfy the Character Grouping
requirement.
3. ES and ON, followed by zero or more NSM, is not allowed in the
last position
* L ON and L ES both fail the Character Grouping requirement.
4. If an L is present, no R, AL or AN may be present, and vice
versa.
5. If an EN is present, no AN may be present, and vice versa.
6. The first character may not be an NSM
7. The first character may not be an EN (European Number) or an AN
(Arabic Number).
* If the character on both sides of a CS is an EN or an AN, the
labels fail the Character Grouping requirement.
* Some domain names where some of the labels use leading EN and
AN may be problem-free, but there's no way of verifying this
while looking at a single label in isolation.
* NOTE: This is a restriction on ASCII labels when used together
with IDNA labels. This is a change from the existing rules
for ASCII labels.
* We could achieve stability by barring numbers at the end of
labels, but this may be more disruptive in practice.
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5. Other issues in need of resolution
This document concerns itself only with the rules that are needed
when dealing with domain names with characters that have differing
BIDI properties, and considers characters only in terms of their BIDI
properties. All other issues with these scripts have to be
considered in other contexts.
One such issue is the need to keep numbers separate; several scripts,
such as Arabic, have multiple sets of numbers. The algorithm in this
document disallows occurrences of AN-class characters ("Arabic-Indic
digits", U+0660 to U+0669) together with EN-class characters (which
includes "European" digits, U+0030 to U+0039 and "extended Arabic-
Indic digits", U+06F0 to U+06F9), but does not help in preventing the
mixing of, for instance, Bengali digits (U+09E6 to U+09EF) and
Gujarati digits (U+0AE6 to U+0AEF), both of which have BIDI class L.
Any registry or script community that wishes to create rules for the
mixing of digits in a label will have to specify these restrictions
at the registry level.
Another set of issues concerns the proper display of IDNs with a
mixture of LTR and RTL labels, or only RTL labels.
It is unrealistic to expect that applications will display domain
names using embedded formatting codes between their labels (for one
thing, no reliable algorithm for identifying domain names in running
text exist); thus, the display order will be determined by the
bidirectional algorithm. Thus, a sequence (in network order) of
R1.R2.ltr will be displayed in the order 2R.1R.ltr in a LTR context,
which might surprise someone expecting to see labels displayed in
hierarchical order. Again, this memo does not attempt to suggest a
solution to this problem.
6. Compatibility considerations
6.1. Backwards compatibility considerations
As with any change to an existing standard, it is important to
consider what happens with existing implementations when the change
is introduced. The following troublesome cases have been noted:
o Old program used to input the newly allowed string. If the old
program checks the input against RFC 3454, the string will not be
allowed, and that domain name will remain inaccessible.
o Old program is asked to display the newly allowed string, and
checks it against RFC 3454 before displaying. The program will
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perform some kind of fallback, most likely displaying the Punycode
form of the string.
o Old program tries to display the newly allowed string. If the old
program has code for displaying the last character of a string
that is different from the code used to display the characters in
the middle of the string, display may be inconsistent and cause
confusion.
One particular example of the last case is if a program chooses to
examine the last character (in network order) of a string in order to
determine its directionality, rather than its first; if it finds an
NSM character and tries to display the string as if it was a left-to-
right string, the resulting display may be interesting, but not
useful.
The editors believe that these cases will have less harmful impact in
practice than continuing to deny the use of words from the languages
for which these strings are necessary as IDN labels.
This specification forbids using leading European numbers in ASCII-
only labels; this is in conflict with a large installed base of such
labels. The harm resulting from violating this rule is seen when a
label at the next level down in the hierarchy ends with a number
(Arabic or European). Zone managers, both registries and private
zone managers, can check for this particular condition before they
allow registration of any string with right-to-left characters in it;
generally it is best to not allow registration of any right-to-left
strings in a zone where the label at the level above begins with a
digit.
6.2. Forward compatibiltiy considerations
This text is, intentionally, specified strictly in terms of the
Unicode BIDI properties. The determination that the condition is
sufficient to fulfil the criteria depends on the Unicode BIDI
algorithm; it is unlikely that drastic changes will be made to this
algorithm.
However, the determination of validity for any string depends on the
Unicode BIDI property values, which are not declared immutable by the
Unicode Consortium. Furthermore, the behaviour of the algorithm for
any given character is likely to be linguistically and culturally
sensitive, so that it's not unlikely that later versions of the
Unicode standard may change the BIDI properties assigned to certain
Unicode characters.
This memo does not propose a solution for this problem.
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7. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
8. Security Considerations
This modification will allow some strings to be used in Stringprep
contexts that are not allowed today. It is possible that differences
in the interpretation of the specification between old and new
implementations could pose a security risk, but it is difficult to
envision any specific instantiation of this.
Any rational attempt to compute, for instance, a hash over an
identifier processed by Stringprep would use network order for its
computation, and thus be unaffected by the changes proposed here.
While it is not believed to pose a problem, if display routines had
been written with specific knowledge of the RFC 3454 Stringprep
prohibitions, it is possible that the potential problems noted under
"backwards compatibility" could cause new kinds of confusion.
The rule about leading numbers, which is more restrictive than
current practice for domain names, has a peculiar interaction with
the DNAME record; a DNAME record can point to a zone where right-to-
left labels are registered without the knowledge or consent of the
zone owner; if the name of the DNAME begins with a number, this can
cause display of the right-to-left labels in the zone to be
confusing. It is recommended that DNAMEs pointing to zones allowing
right-to-left labels should not start with a digit, but a pointed-to
zone owner has no way of enforcing this.
9. Acknowledgements
While the listed editors held the pen, this document represents the
joint work and conclusions of an ad hoc design team. In addition to
the editors this consisted of, in alphabetic order, Tina Dam, Patrik
Faltstrom, and John Klensin. Many further specific contributions and
helpful comments were received from the people listed below, and
others who have contributed to the development and use of the IDNA
protocols.
The team wishes in particular to thank Roozbeh Pournader for calling
its attention to the issue with the Thaana script, Paul Hoffmann for
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pointing out the need to be explicit about backwards compatibility
considerations, Ken Whistler for suggesting the basis of the
formalized "character grouping" requirement, Mark Davis for
commentary, and Erik van der Poel for careful review, comments and
verification of the rulesets.
10. References
10.1. Normative references
[I-D.ietf-idnabis-rationale]
Klensin, J., "Internationalizing Domain Names for
Applications (IDNA): Definitions, Background and
Rationale", draft-ietf-idnabis-rationale-00 (work in
progress), May 2008.
[UAX9] Davis, M., "Unicode Standard Annex #9: The Bidirectional
Algorithm, revision 15", 03 2005.
10.2. Informative references
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
Appendix A. Change log
This appendix is intended to be removed by the RFC Editor when this
document is published as an RFC.
A.1. Changes from draft-alvestrand-00 to -01
Suggested a possible new algorithm.
Multiple smaller changes.
A.2. Changes from -01 to -02
Date of publication updated.
Change log added.
A.3. Changes from -02 to -03
Intro changed to reflect addressing the deeper issues with the BIDI
algorithm.
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Gave formalized criteria for "valid strings", and documented the new
set of requirements for strings that satisfy the criteria.
Removed most of section 5, "Other problems", and noted that this memo
focuses ONLY on issues that can be evaluated by looking at the BIDI
properties of characters.
A.4. Changes from -03 to -04
Added back AN to the list of allowed characters; it had been left out
by accident in -03.
Removed some rules that were redundant.
Added some considerations for backwards compatibility and interaction
with ASCII labels that start with a number.
Mentioned the issue with DNAME pointing to a zone containing RTL
labels in the security considerations section.
Wording updates in multiple places, including some spelling errors.
Rewrote the introduction section.
Split references into "normative" and "informative".
A.5. Changes from draft-alvestrand-04 to draft-ietf -00
Changed name of draft.
Added a couple of "note in draft" statements to remind the WG of open
issues.
Noted that BIDI controls in the paragraph are unproblematic with the
given ruleset.
A.6. Changes from idnabis -00 to -01
Added text to section 5 describing issues with mixture of numbers in
labels
Addressed some of the issues raised by Mark Davis in March 2008 in
regard to document clarity.
Changed the formulation of the label uniqueness requirement to be
consistent with the text under "Labels with numbers".
Spell-checked document.
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Authors' Addresses
Harald Tveit Alvestrand (editor)
Google
Beddingen 10
Trondheim, 7014
Norway
Email: harald@alvestrand.no
Cary Karp (editor)
Swedish Museum of Natural History
Frescativ. 40
Stockholm, 10405
Sweden
Phone: +46 8 5195 4055
Fax:
Email: ck@nrm.museum
URI:
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