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<h2 style="text-align: center">
Unicode Technical
Standard #35
</h2>
<h1>
Unicode Locale Data Markup Language (LDML)<br>Part 5: Collation
</h1>
<!-- This header table should be identical across the parts of this UTS. -->
<table border="1" cellpadding="2" cellspacing="0" class="wide">
<tr>
<td>Version</td>
<td>32</td>
</tr>
<tr>
<td>Editors</td>
<td><a
href="https://plus.google.com/117587389715494866571?rel=author">
Markus Scherer</a> (<a href="mailto:markus.icu@gmail.com">markus.icu@gmail.com</a>)
and <a href="tr35.html#Acknowledgments">other CLDR committee
members</a></td>
</tr>
</table>
<p>
For the full header, summary, and status, see <a href="tr35.html">
Part 1: Core</a>
</p>
<h3>
<i>Summary</i>
</h3>
<p>
This document describes parts of an XML format (<i>vocabulary</i>)
for the exchange of structured locale data. This format is used in
the <a href="http://cldr.unicode.org/">Unicode Common Locale Data
Repository</a>.
</p>
<p>
This is a partial document, describing only those parts of the LDML
that are relevant for collation (sorting, searching &amp; grouping).
For the other parts of the LDML see the <a href="tr35.html">main
LDML document</a> and the links above.
</p>
<h3>
<i>Status</i>
</h3>
<!-- NOT YET APPROVED
<p>
<i class="changed">This is a<b><font color="#ff3333">
draft </font></b>document which may be updated, replaced, or superseded by
other documents at any time. Publication does not imply endorsement
by the Unicode Consortium. This is not a stable document; it is
inappropriate to cite this document as other than a work in
progress.
</i>
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<!-- APPROVED -->
<p>
<i>This document has been reviewed by Unicode members and other
interested parties, and has been approved for publication by the
Unicode Consortium. This is a stable document and may be used as
reference material or cited as a normative reference by other
specifications.</i>
</p>
<!-- END APPROVED -->
<blockquote>
<p>
<i><b>A Unicode Technical Standard (UTS)</b> is an independent
specification. Conformance to the Unicode Standard does not imply
conformance to any UTS.</i>
</p>
</blockquote>
<p>
<i>Please submit corrigenda and other comments with the CLDR bug
reporting form [<a href="tr35.html#Bugs">Bugs</a>]. Related
information that is useful in understanding this document is found
in the <a href="tr35.html#References">References</a>. For the latest
version of the Unicode Standard see [<a href="tr35.html#Unicode">Unicode</a>].
For a list of current Unicode Technical Reports see [<a
href="tr35.html#Reports">Reports</a>]. For more information about
versions of the Unicode Standard, see [<a href="tr35.html#Versions">Versions</a>].
</i>
</p>
<h2>
<a name="Parts" href="#Parts">Parts</a>
</h2>
<!-- This section of Parts should be identical in all of the parts of this UTS. -->
<p>The LDML specification is divided into the following parts:</p>
<ul class="toc">
<li>Part 1: <a href="tr35.html#Contents">Core</a> (languages,
locales, basic structure)
</li>
<li>Part 2: <a href="tr35-general.html#Contents">General</a>
(display names &amp; transforms, etc.)
</li>
<li>Part 3: <a href="tr35-numbers.html#Contents">Numbers</a>
(number &amp; currency formatting)
</li>
<li>Part 4: <a href="tr35-dates.html#Contents">Dates</a> (date,
time, time zone formatting)
</li>
<li>Part 5: <a href="tr35-collation.html#Contents">Collation</a>
(sorting, searching, grouping)
</li>
<li>Part 6: <a href="tr35-info.html#Contents">Supplemental</a>
(supplemental data)
</li>
<li>Part 7: <a href="tr35-keyboards.html#Contents">Keyboards</a>
(keyboard mappings)
</li>
</ul>
<h2>
<a name="Contents" href="#Contents">Contents of Part 5, Collation</a>
</h2>
<!-- START Generated TOC: CheckHtmlFiles -->
<ul class="toc">
<li>1 <a href="#CLDR_Collation">CLDR Collation</a>
<ul class="toc">
<li>1.1 <a href="#CLDR_Collation_Algorithm">CLDR Collation
Algorithm</a>
<ul class="toc">
<li>1.1.1 <a href="#Algorithm_FFFE">U+FFFE</a></li>
<li>1.1.2 <a href="#Context_Sensitive_Mappings">Context-Sensitive
Mappings</a></li>
<li>1.1.3 <a href="#Algorithm_Case">Case Handling</a></li>
<li>1.1.4 <a href="#Algorithm_Reordering_Groups">Reordering
Groups</a></li>
<li>1.1.5 <a href="#Combining_Rules">Combining Rules</a></li>
</ul>
</li>
</ul>
</li>
<li>2 <a href="#Root_Collation">Root Collation</a>
<ul class="toc">
<li>2.1 <a href="#grouping_classes_of_characters">Grouping
classes of characters</a></li>
<li>2.2 <a href="#non_variable_symbols">Non-variable
symbols</a></li>
<li>2.3 <a href="#tibetan_contractions">Additional
contractions for Tibetan</a></li>
<li>2.4 <a href="#tailored_noncharacter_weights">Tailored
noncharacter weights</a></li>
<li>2.5 <a href="#Root_Data_Files">Root Collation Data
Files</a></li>
<li>2.6 <a href="#Root_Data_File_Formats">Root Collation
Data File Formats</a>
<ul class="toc">
<li>2.6.1 <a href="#File_Format_allkeys_CLDR_txt">allkeys_CLDR.txt</a></li>
<li>2.6.2 <a href="#File_Format_FractionalUCA_txt">FractionalUCA.txt</a></li>
<li>2.6.3 <a href="#File_Format_UCA_Rules_txt">UCA_Rules.txt</a></li>
</ul>
</li>
</ul>
</li>
<li>3 <a href="#Collation_Tailorings">Collation Tailorings</a>
<ul class="toc">
<li>3.1 <a href="#Collation_Types">Collation Types</a>
<ul class="toc">
<li>3.1.1 <a href="#Collation_Type_Fallback">Collation
Type Fallback</a>
<ul class="toc">
<li>Table: <a
href="#Sample_requested_and_actual_collation_locales_and_types">Sample
requested and actual collation locales and types</a></li>
</ul>
</li>
</ul>
</li>
<li>3.2 <a href="#Collation_Version">Version</a></li>
<li>3.3 <a href="#Collation_Element">Collation Element</a></li>
<li>3.4 <a href="#Setting_Options">Setting Options</a>
<ul class="toc">
<li>Table: <a href="#Collation_Settings">Collation
Settings</a></li>
<li>3.4.1 <a href="#Common_Settings">Common settings
combinations</a></li>
<li>3.4.2 <a href="#Normalization_Setting">Notes on the
normalization setting</a></li>
<li>3.4.3 <a href="#Variable_Top_Settings">Notes on
variable top settings</a></li>
</ul>
</li>
<li>3.5 <a href="#Rules">Collation Rule Syntax</a></li>
<li>3.6 <a href="#Orderings">Orderings</a>
<ul class="toc">
<li>Table: <a href="#Specifying_Collation_Ordering">Specifying
Collation Ordering</a></li>
<li>Table: <a href="#Abbreviating_Ordering_Specifications">Abbreviating
Ordering Specifications</a></li>
</ul>
</li>
<li>3.7 <a href="#Contractions">Contractions</a>
<ul class="toc">
<li>Table: <a href="#Specifying_Contractions">Specifying
Contractions</a></li>
</ul>
</li>
<li>3.8 <a href="#Expansions">Expansions</a></li>
<li>3.9 <a href="#Context_Before">Context Before</a>
<ul class="toc">
<li>Table: <a href="#Specifying_Previous_Context">Specifying
Previous Context</a></li>
</ul>
</li>
<li>3.10 <a href="#Placing_Characters_Before_Others">Placing
Characters Before Others</a></li>
<li>3.11 <a href="#Logical_Reset_Positions">Logical Reset
Positions</a>
<ul class="toc">
<li>Table: <a href="#Specifying_Logical_Positions">Specifying
Logical Positions</a></li>
</ul>
</li>
<li>3.12 <a href="#Special_Purpose_Commands">Special-Purpose
Commands</a>
<ul class="toc">
<li>Table: <a href="#Special_Purpose_Elements">Special-Purpose
Elements</a></li>
</ul>
</li>
<li>3.13 <a href="#Script_Reordering">Collation Reordering</a>
<ul class="toc">
<li>3.13.1 <a href="#Interpretation_reordering">Interpretation
of a reordering list</a></li>
<li>3.13.2 <a href="#Reordering_Groups_allkeys">Reordering
Groups for allkeys.txt</a></li>
</ul>
</li>
<li>3.14 <a href="#Case_Parameters">Case Parameters</a>
<ul class="toc">
<li>3.14.1 <a href="#Case_Untailored">Untailored
Characters</a></li>
<li>3.14.2 <a href="#Case_Weights">Compute Modified
Collation Elements</a></li>
<li>3.14.3 <a href="#Case_Tailored">Tailored Strings</a></li>
</ul>
</li>
<li>3.15 <a href="#Visibility">Visibility</a></li>
<li>3.16 <a href="#Collation_Indexes">Collation Indexes</a>
<ul class="toc">
<li>3.16.1 <a href="#Index_Characters">Index Characters</a></li>
<li>3.16.2 <a href="#CJK_Index_Markers">CJK Index
Markers</a></li>
</ul>
</li>
</ul>
</li>
</ul>
<!-- END Generated TOC: CheckHtmlFiles -->
<h2>
1 <a name="CLDR_Collation" href="#CLDR_Collation">CLDR Collation</a>
</h2>
<p>Collation is the general term for the process and function of
determining the sorting order of strings of characters, for example
for lists of strings presented to users, or in databases for sorting
and selecting records.</p>
<p>Collation varies by language, by application (some languages
use special phonebook sorting), and other criteria (for example,
phonetic vs. visual).</p>
<p>
CLDR provides collation data for many languages and styles. The data
supports not only sorting but also language-sensitive searching and
grouping under index headers. All CLDR collations are based on the [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>] default
order, with common modifications applied in the CLDR root collation,
and further tailored for language and style as needed.
</p>
<h3>
1.1 <a name="CLDR_Collation_Algorithm"
href="#CLDR_Collation_Algorithm">CLDR Collation Algorithm</a>
</h3>
<p>
The CLDR collation algorithm is an extension of the <a
href="http://www.unicode.org/reports/tr10/#Main_Algorithm">Unicode
Collation Algorithm</a>.
</p>
<h4>
1.1.1 <a name="Algorithm_FFFE" href="#Algorithm_FFFE">U+FFFE</a>
</h4>
<p>
U+FFFE maps to a CE with a minimal, unique primary weight. Its
primary weight is not "variable": U+FFFE must not become ignorable in
alternate handling. On the identical level, a minimal, unique
“weight” must be emitted for U+FFFE as well. This allows for <a
href="http://www.unicode.org/reports/tr10/#Merging_Sort_Keys">Merging
Sort Keys</a> within code point space.
</p>
<p>
For example, when sorting names in a database, a sortable string can
be formed with <em>last_name</em> + '\uFFFE' + <em>first_name</em>.
These strings would sort properly, without ever comparing the last
part of a last name with the first part of another first name.
</p>
<p>
For backwards secondary level sorting, text <i>segments</i> separated
by U+FFFE are processed in forward segment order, and <i>within</i>
each segment the secondary weights are compared backwards. This is so
that such combined strings are processed consistently with merging
their sort keys (for example, by concatenating them level by level
with a low separator).
</p>
<p class="note">
Note: With unique, low weights on <i>all</i> levels it is possible to
achieve
<code>sortkey(str1 + "\uFFFE" + str2) ==
mergeSortkeys(sortkey(str1), sortkey(str2))</code>
. When that is not necessary, then code can be a little simpler (no
special handling for U+FFFE except for backwards-secondary), sort
keys can be a little shorter (when using compressible common
non-primary weights for U+FFFE), and another low weight can be used
in tailorings.
</p>
<h4>
1.1.2 <a name="Context_Sensitive_Mappings"
href="#Context_Sensitive_Mappings">Context-Sensitive Mappings</a>
</h4>
<p>Contraction matching, as in the UCA, starts from the first
character of the contraction string. It slows down processing of that
first character even when none of its contractions matches. In some
cases, it is preferrable to change such contractions to mappings with
a prefix (context before a character), so that complex processing is
done only when the less-frequently occurring trailing character is
encountered.</p>
<p>For example, the DUCET contains contractions for several
variants of L· (L followed by middle dot). Collating ASCII text is
slowed down by contraction matching starting with L/l. In the CLDR
root collation, these contractions are replaced by prefix mappings
(L|·) which are triggered only when the middle dot is encountered.
CLDR also uses prefix rules in the Japanese tailoring, for processing
of Hiragana/Katakana length and iteration marks.</p>
<p>The mapping is conditional on the prefix match but does not
change the mappings for the preceding text. As a result, a
contraction mapping for "px" can be replaced by a prefix rule "p|x"
only if px maps to the collation elements for p followed by the
collation elements for "x if after p". In the DUCET, L· maps to CE(L)
followed by a special secondary CE (which differs from CE(·) when ·
is not preceded by L). In the CLDR root collation, L has no
context-sensitive mappings, but · maps to that special secondary CE
if preceded by L.</p>
<p>A prefix mapping for p|x behaves mostly like the contraction
px, except when there is a contraction that overlaps with the prefix,
for example one for "op". A contraction matches only new text (and
consumes it), while a prefix matches only already-consumed text.</p>
<ul>
<li>With mappings for "op" and "px", only the first contraction
matches in text "opx". (It consumes the "op" characters, and there
is no context-sensitive mapping for x.)</li>
<li>With mappings for "op" and "p|x", both the contraction and
the prefix rule match in text "opx". (The prefix always matches
already-consumed characters, regardless of whether they mapped as
part of contractions.)</li>
</ul>
<p class="note">
Note: Matching of discontiguous contractions should be implemented
without rewriting the text (unlike in the [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>] algorithm
specification), so that prefix matching is predictable. (It should
also help with contraction matching performance.) An implementation
that does rewrite the text, as in the UCA, will get different results
for some (unusual) combinations of contractions, prefix rules, and
input text.
</p>
<p>Prefix matching uses a simple longest-match algorithm (op|c
wins over p|c). It is recommended that prefix rules be limited to
mappings where both the prefix string and the mapped string begin
with an NFC boundary (that is, with a normalization starter that does
not combine backwards). (In op|ch both o and c should be starters
(ccc=0) and NFC_QC=Yes.) Otherwise, prefix matching would be affected
by canonical reordering and discontiguous matching, like
contractions. Prefix matching is thus always contiguous.</p>
<p>A character can have mappings with both prefixes (context
before) and contraction suffixes. Prefixes are matched first. This is
to keep them reasonably implementable: When there is a mapping with
both a prefix and a contraction suffix (like in Japanese: ぐ|ゞ), then
the matching needs to go in both directions. The contraction might
involve discontiguous matching, which needs complex text iteration
and handling of skipped combining marks, and will consume the
matching suffix. Prefix matching should be first because, regardless
of whether there is a match, the implementation will always return to
the original text index (right after the prefix) from where it will
start to look at all of the contractions for that prefix.</p>
<p>If there is a match for a prefix but no match for any of the
suffixes for that prefix, then fall back to mappings with the
next-longest matching prefix, and so on, ultimately to mappings with
no prefix. (Otherwise mappings with longer prefixes would “hide”
mappings with shorter prefixes.)</p>
<p>Consider the following mappings.</p>
<ol>
<li>p → CE(p)</li>
<li>h → CE(h)</li>
<li>c → CE(c)</li>
<li>ch → CE(d)</li>
<li>p|c → CE(u)</li>
<li>p|ci → CE(v)</li>
<li>p|ĉ → CE(w)</li>
<li>op|ck → CE(x)</li>
</ol>
<p>With these, text collates like this:</p>
<ul>
<li>pc → CE(p)CE(u)</li>
<li>pci → CE(p)CE(v)</li>
<li>pch → CE(p)CE(u)CE(h)</li>
<li>pĉ → CE(p)CE(w)</li>
<li>pĉ̣ → CE(p)CE(w)CE(U+0323) // discontiguous</li>
<li>opck → CE(o)CE(p)CE(x)</li>
<li>opch → CE(o)CE(p)CE(u)CE(h)</li>
</ul>
<p>
However, if the mapping p|c → CE(u) is missing, then text "pch" maps
to CE(p)CE(d), "opch" maps to CE(o)CE(p)CE(d), and "pĉ̣" maps to
CE(p)CE(c)CE(U+0323)CE(U+0302) (because discontiguous contraction
matching extends <i>an existing match</i> by one non-starter at a
time).
</p>
<h4>
1.1.3 <a name="Algorithm_Case" href="#Algorithm_Case">Case
Handling</a>
</h4>
<p>
CLDR specifies how to sort lowercase or uppercase first, as a
stronger distinction than other tertiary variants (<strong>caseFirst</strong>)
or while completely ignoring all other tertiary distinctions (<strong>caseLevel</strong>).
See <i>Section 3.3 <a href="#Setting_Options">Setting Options</a></i>
and <i>Section 3.13 <a href="#Case_Parameters">Case
Parameters</a></i>.
</p>
<h4>
1.1.4 <a name="Algorithm_Reordering_Groups"
href="#Algorithm_Reordering_Groups">Reordering Groups</a>
</h4>
<p>CLDR specifies how to do parametric reordering of groups of
scripts (e.g., “native script first”) as well as special groups
(e.g., “digits after letters”), and provides data for the effective
implementation of such reordering.</p>
<h4>
1.1.5 <a name="Combining_Rules"
href="#Combining_Rules">Combining Rules</a>
</h4>
<p>Rules from different sources can be combined, with the later rules overriding the earlier ones. The following is an example of how this can be useful.</p>
<p>There is a root collation for &quot;emoji&quot; in CLDR. So use of &quot;-u-co-emoji&quot; in a Unicode locale identifier will access that ordering. </p>
<p>Example, using ICU:</p>
<blockquote>
<p>collator = Collator.getInstance(ULocale.forLanguageTag(&quot;en-u-co-emoji&quot;)); </p>
</blockquote>
<p>However, use of the emoji will supplant the language's customizations. So the above is the equivalent of: </p>
<blockquote>
<p>collator = Collator.getInstance(ULocale.forLanguageTag(&quot;und-u-co-emoji&quot;)); </p>
</blockquote>
<p>The same structure will not work for a language that does require customization, like Danish. That is, the following will fail.</p>
<blockquote>
<p> collator = Collator.getInstance(ULocale.forLanguageTag(&quot;da-u-co-emoji&quot;)); </p>
</blockquote>
<p>For that, a slightly more cumbersome method needs to be employed, which is to take the rules for Danish, and explicitly add the rules for emoji. </p>
<blockquote>
<p>RuleBasedCollator collator = new RuleBasedCollator(<br>
((RuleBasedCollator) Collator.getInstance(ULocale.forLanguageTag(&quot;da&quot;))).getRules() +<br>
((RuleBasedCollator) Collator.getInstance(ULocale.forLanguageTag(&quot;und-u-co-emoji&quot;)))<br>
.getRules());</p>
</blockquote>
<p>The following table shows the differences. When emoji ordering is supported, the two faces will be adjacent. When Danish ordering is supported, the ü is after the y.</p>
<table class='simple'>
<tbody>
<tr>
<td>code point order</td>
<td>,</td>
<td></td>
<td></td>
<td>Z</td>
<td>a</td>
<td>y</td>
<td>ü</td>
<td>☹️</td>
<td>✈️️</td>
<td>글</td>
<td>😀</td>
</tr>
<tr>
<td>en</td>
<td>,</td>
<td>☹️</td>
<td>✈️️</td>
<td>😀</td>
<td>a</td>
<td>ü</td>
<td>y</td>
<td>Z</td>
<td>글</td>
</tr>
<tr>
<td>en-u-co-emoji</td>
<td>,</td>
<td>😀</td>
<td>☹️</td>
<td>✈️️</td>
<td>a</td>
<td>ü</td>
<td>y</td>
<td>Z</td>
<td>글</td>
</tr>
<tr>
<td>da</td>
<td>,</td>
<td>☹️</td>
<td>✈️️</td>
<td>😀</td>
<td>a</td>
<td>y</td>
<td><strong><u>ü</u></strong></td>
<td>Z</td>
<td>글</td>
</tr>
<tr>
<td>da-u-co-emoji</td>
<td>,</td>
<td>😀</td>
<td>☹️</td>
<td>✈️️</td>
<td>a</td>
<td><strong><u>ü</u></strong></td>
<td>y</td>
<td>Z</td>
<td>글</td>
</tr>
<tr>
<td>combined rules</td>
<td>,</td>
<td>😀</td>
<td>☹️</td>
<td>✈️️</td>
<td>a</td>
<td>y</td>
<td><strong><u>ü</u></strong></td>
<td>Z</td>
<td>글</td>
</tr>
</tbody>
</table>
<br>
<p>&nbsp;</p>
<p> </p>
<h2>
2 <a name="Root_Collation" href="#Root_Collation">Root Collation</a>
</h2>
<p>
The CLDR root collation order is based on the <a
href="http://www.unicode.org/reports/tr10/#Default_Unicode_Collation_Element_Table">Default
Unicode Collation Element Table (DUCET)</a> defined in <em>UTS #10:
Unicode Collation Algorithm</em> [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>]. It is
used by all other locales by default, or as the base for their
tailorings. (For a chart view of the UCA, see Collation Chart [<a
href="tr35.html#UCAChart">UCAChart</a>].)
</p>
<p>Starting with CLDR 1.9, CLDR uses modified tables for the root
collation order. The root locale ordering is tailored in the
following ways:</p>
<h3>
2.1 <a name="grouping_classes_of_characters"
href="#grouping_classes_of_characters">Grouping classes of
characters</a>
</h3>
<p>As of Version 6.1.0, the DUCET puts characters into the
following ordering:</p>
<ul>
<li>First &quot;common characters&quot;: whitespace,
punctuation, general symbols, some numbers, currency symbols, and
other numbers.</li>
<li>Then &quot;script characters&quot;: Latin, Greek, and the
rest of the scripts.</li>
</ul>
<p>(There are a few exceptions to this general ordering.)</p>
<p>The CLDR root locale modifies the DUCET tailoring by ordering
the common characters more strictly by category:</p>
<ul>
<li>whitespace, punctuation, general symbols, currency symbols,
and numbers.</li>
</ul>
<p>What the regrouping allows is for users to parametrically
reorder the groups. For example, users can reorder numbers after all
scripts, or reorder Greek before Latin.</p>
<p>The relative order within each of these groups still matches
the DUCET. Symbols, punctuation, and numbers that are grouped with a
particular script stay with that script. The differences between CLDR
and the DUCET order are:</p>
<ol>
<li>CLDR groups the numbers together after currency symbols,
instead of splitting them with some before and some after. Thus the
following are put <em>after</em> currencies and just before all the
other numbers.
<blockquote>
<p>
U+09F4 ( ৴ ) [No] BENGALI CURRENCY NUMERATOR ONE<br> ...<br>
U+1D371 ( 𝍱 ) [No] COUNTING ROD TENS DIGIT NINE
</p>
</blockquote>
</li>
<li>CLDR handles a few other characters differently
<ol>
<li>U+10A7F ( 𐩿 ) [Po] OLD SOUTH ARABIAN NUMERIC INDICATOR is
put with punctuation, not symbols</li>
<li>U+20A8 ( ₨ ) [Sc] RUPEE SIGN and U+FDFC ( ﷼ ) [Sc] RIAL
SIGN are put with currency signs, not with R and REH.</li>
</ol>
</li>
</ol>
<h3>
2.2 <a name="non_variable_symbols" href="#non_variable_symbols">Non-variable
symbols</a>
</h3>
<p>
There are multiple <a
href="http://www.unicode.org/reports/tr10/#Variable_Weighting">Variable-Weighting</a>
options in the UCA for symbols and punctuation, including <em>non-ignorable</em>
and <em>shifted</em>. With the <em>shifted</em> option, almost all
symbols and punctuation are ignored—except at a fourth level. The
CLDR root locale ordering is modified so that symbols are not
affected by the <em>shifted</em> option. That is, by default, symbols
are not “variable” in CLDR. So <em>shifted</em> only causes
whitespace and punctuation to be ignored, but not symbols (like ♥).
The DUCET behavior can be specified with a locale ID using the
&quot;kv&quot; keyword, to set the Variable section to include all of
the symbols below it, or be set parametrically where implementations
allow access.
</p>
<p>See also:</p>
<ul>
<li><i>Section 3.3, <a href="#Setting_Options">Setting
Options</a></i></li>
<li><a href="http://www.unicode.org/charts/collation/">http://www.unicode.org/charts/collation/</a></li>
</ul>
<h3>
2.3 <a name="tibetan_contractions" href="#tibetan_contractions">Additional
contractions for Tibetan</a>
</h3>
<p>
Ten contractions are added for Tibetan: Two to fulfill <a
href="http://www.unicode.org/reports/tr10/#WF5">well-formedness
condition 5</a>, and eight more to preserve the default order for
Tibetan. For details see <i>UTS #10, Section 3.8.2, <a
href="http://www.unicode.org/reports/tr10/#Well_Formed_DUCET">Well-Formedness
of the DUCET</a></i>.
</p>
<h3>
2.4 <a name="tailored_noncharacter_weights"
href="#tailored_noncharacter_weights">Tailored noncharacter
weights</a>
</h3>
<p>U+FFFE and U+FFFF have special tailorings:</p>
<blockquote>
<p>
<strong>U+FFFF: </strong>This code point is tailored to have a
primary weight higher than all other characters. This allows the
reliable specification of a range, such as &ldquo;Sch&rdquo; ≤ X ≤
&ldquo;Sch\uFFFF&rdquo;, to include all strings starting with
&quot;sch&quot; or equivalent.
</p>
<p>
<strong>U+FFFE: </strong>This code point produces a CE with minimal,
unique weights on primary and identical levels. For details see the
<i><a href="#Algorithm_FFFE">CLDR Collation Algorithm</a></i> above.
</p>
</blockquote>
<p>
UCA (beginning with version 6.3) also maps <strong>U+FFFD</strong> to
a special collation element with a very high primary weight, so that
it is reliably non-<a
href="http://www.unicode.org/reports/tr10/#Variable_Weighting">variable</a>,
for use with <a
href="http://www.unicode.org/reports/tr10/#Handling_Illformed">ill-formed
code unit sequences</a>.
</p>
<p>
In CLDR, so as to maintain the special collation elements, <strong>U+FFFD..U+FFFF
</strong> are not further tailorable, and nothing can tailor to them. That is,
neither can occur in a collation rule. For example, the following
rules are illegal:
</p>
<p>
<code>&amp;\uFFFF &lt; x</code>
</p>
<p>
<code>&amp;x &lt;\uFFFF</code>
<br>
</p>
<p class="note">
<b>Note:</b>
</p>
<ul>
<li class="note">Java uses an early version of this collation
syntax, but has not been updated recently. It does not support any
of the syntax marked with [...], and its default table is not the
DUCET nor the CLDR root collation.</li>
</ul>
<h3>
2.5 <a name="Root_Data_Files" href="#Root_Data_Files">Root
Collation Data Files</a>
</h3>
<p>
The CLDR root collation data files are in the CLDR repository and
release, under the path <a
href="http://unicode.org/repos/cldr/tags/latest/common/uca/">common/uca/</a>.
</p>
<p>
For most data files there are <strong>_SHORT</strong> versions
available. They contain the same data but only minimal comments, to
reduce the file sizes.
</p>
<p>Comments with DUCET-style weights in files other than
allkeys_CLDR.txt and allkeys_DUCET.txt use the weights defined in
allkeys_CLDR.txt.</p>
<ul>
<li><strong>allkeys_CLDR</strong> - A file that provides a
remapping of UCA DUCET weights for use with CLDR.</li>
<li><strong>allkeys_DUCET</strong> - The same as DUCET
allkeys.txt, but in alternate=non-ignorable sort order, for easier
comparison with allkeys_CLDR.txt.</li>
<li><strong>FractionalUCA</strong> - A file that provides a
remapping of UCA DUCET weights for use with CLDR. The weight values
are modified:
<ul>
<li>The weights have variable length, with 1..4 bytes each.
Each secondary or tertiary weight currently uses at most 2 bytes.</li>
<li>There are tailoring gaps between adjacent weights, so that
a number of characters can be tailored to sort between any two
root collation elements.</li>
<li>There are collation elements with primary weights at the
boundaries between reordering groups and Unicode scripts, so that
tailoring around the first or last primary of a group/script
results in new collation elements that sort and reorder together
with that group or script. These boundary weights also define the
primary weight ranges for parametric group and script reordering.
</li>
</ul> An implementation may modify the weights further to fit the needs
of its data structures.</li>
<li><strong>UCA_Rules</strong> - A file that specifies the root
collation order in the form of <a href="#Collation_Tailorings">tailoring
rules</a>. This is only an approximation of the FractionalUCA data,
since the rule syntax cannot express every detail of the collation
elements. For example, in the DUCET and in FractionalUCA, tertiary
differences are usually expressed with special tertiary weights on
all collation elements of an expansion, while a typical from-rules
builder will modify the tertiary weight of only one of the collation
elements.</li>
<li><strong>CollationTest_CLDR</strong> - The CLDR versions of
the CollationTest files, which use the tailorings for CLDR. For
information on the format, see <a
href="http://www.unicode.org/Public/UCA/latest/CollationTest.html">CollationTest.html</a>
in the <a href="http://www.unicode.org/reports/tr10/#Data10">UCA
data directory</a>.
<ul>
<li>CollationTest_CLDR_NON_IGNORABLE.txt</li>
<li>CollationTest_CLDR_SHIFTED.txt</li>
</ul></li>
</ul>
<h3>
2.6 <a name="Root_Data_File_Formats" href="#Root_Data_File_Formats">Root
Collation Data File Formats</a>
</h3>
<p>The file formats may change between versions of CLDR. The
formats for CLDR 23 and beyond are as follows. As usual, text after a
# is a comment.</p>
<h4>
2.6.1 <a name="File_Format_allkeys_CLDR_txt"
href="#File_Format_allkeys_CLDR_txt">allkeys_CLDR.txt</a>
</h4>
<p>
This file defines CLDR’s tailoring of the DUCET, as described in <i>Section
2, <a href="#Root_Collation">Root Collation</a>
</i>.
</p>
<p>
The format is similar to that of <a
href="http://www.unicode.org/reports/tr10/#File_Format">allkeys.txt</a>,
although there may be some differences in whitespace.
</p>
<h4>
2.6.2 <a name="File_Format_FractionalUCA_txt"
href="#File_Format_FractionalUCA_txt">FractionalUCA.txt</a>
</h4>
<p>The format is illustrated by the following sample lines, with
commentary afterwards.</p>
<pre>[UCA version = 6.0.0]</pre>
<blockquote>
<p>Provides the version number of the UCA table.</p>
</blockquote>
<pre>[Unified_Ideograph 4E00..9FCC FA0E..FA0F FA11 FA13..FA14 FA1F FA21 FA23..FA24 FA27..FA29 3400..4DB5 20000..2A6D6 2A700..2B734 2B740..2B81D]</pre>
<blockquote>
<p>
Lists the ranges of Unified_Ideograph characters in collation order.
(New in CLDR 24.) They map to collation elements with <a
href="http://www.unicode.org/reports/tr10/#Implicit_Weights">implicit
(constructed) primary weights</a>.
</p>
</blockquote>
<pre>[radical 6=⼅亅:亅𠄌了𠄍-𠄐亇𠄑予㐧𠄒-𠄔争𠀩𠄕亊𠄖-𠄘𪜜事㐨𠄙-𠄛𪜝𠄜𠄝]
[radical 210=⿑齊:齊𪗄𪗅齋䶒䶓𪗆齌𠆜𪗇𪗈齍𪗉-𪗌齎𪗎𪗍齏𪗏-𪗓]
[radical 210'=⻬齐:齐齑]
[radical end]</pre>
<blockquote>
<p>
Data for Unihan radical-stroke order. (New in CLDR 26.) Following
the [Unified_Ideograph] line, a section of
<code>[radical ...]</code>
lines defines a radical-stroke order of the Unified_Ideograph
characters.
</p>
<p>
For Han characters, an implementation may choose either to implement
the order defined in the UCA and the [Unified_Ideograph] data, or to
implement the order defined by the
<code>[radical ...]</code>
lines. Beginning with CLDR 26, the CJK type="unihan" tailorings
assume that the root collation order sorts Han characters in Unihan
radical-stroke order according to the
<code>[radical ...]</code>
data. The CollationTest_CLDR files only contain Han characters that
are in the same relative order using implicit weights or the
radical-stroke order.
</p>
<p>
The root collation radical-stroke order is derived from the first
(normative) values of the <a
href="http://www.unicode.org/reports/tr38/#kRSUnicode">Unihan
kRSUnicode</a> field for each Han character. Han characters are ordered
by radical, with traditional forms sorting before simplified ones.
Characters with the same radical are ordered by residual stroke
count. Characters with the same radical-stroke values are ordered by
block and code point, as for <a
href="http://www.unicode.org/reports/tr10/#Implicit_Weights">UCA
implicit weights</a>.
</p>
<p>
There is one
<code>[radical ...]</code>
line per radical, in the order of radical numbers. Each line shows
the radical number and the representative characters from the <a
href="http://www.unicode.org/reports/tr44/#UCD_Files_Table">UCD
file CJKRadicals.txt</a>, followed by a colon (“:”) and the Han
characters with that radical in the order as described above. A
range like
<code>万-丌</code>
indicates that the code points in that range sort in code point
order.
</p>
<p>
The radical number and characters are informational. The sort order
is established only by the order of the
<code>[radical ...]</code>
lines, and within each line by the characters and ranges between the
colon (“:”) and the bracket (“]”).
</p>
<p>
Each Unified_Ideograph occurs exactly once. Only Unified_Ideograph
characters are listed on
<code>[radical ...]</code>
lines.
</p>
<p>
This section is terminated with one
<code>[radical end]</code>
line.
</p>
</blockquote>
<pre>0000; [,,] # Zyyy Cc [0000.0000.0000] * &lt;NULL&gt;</pre>
<blockquote>
<p>
Provides a weight line. The first element (before the &quot;;&quot;)
is a hex codepoint sequence. The second field is a sequence of
collation elements. Each collation element has 3 parts separated by
commas: the primary weight, secondary weight, and tertiary weight.
The tertiary weight actually consists of two components: the top two
bits (0xC0) are used for the <em>case level</em>, and should be
masked off where a case level is not used.
</p>
<p>A weight is either empty (meaning a zero or ignorable weight)
or is a sequence of one or more bytes. The bytes are interpreted as
a &quot;fraction&quot;, meaning that the ordering is 04 &lt; 05 05
&lt; 06. The weights are constructed so that no weight is an initial
subsequence of another: that is, having both the weights 05 and 05
05 is illegal. The above line consists of all ignorable weights.</p>
<p>The vertical bar (“|”) character is used to indicate context,
as in:</p>
</blockquote>
<pre>006C | 00B7; [, DB A9, 05]</pre>
<blockquote>
This example indicates that if U+00B7 appears immediately after
U+006C, it is given the corresponding collation element instead. This
syntax is roughly equivalent to the following contraction, but is
more efficient. For details see the specification of <i><a
href="#Context_Sensitive_Mappings">Context-Sensitive Mappings</a></i>
above.
</blockquote>
<pre>006C 00B7; <em>CE(006C)</em> [, DB A9, 05]</pre>
<blockquote>
<p>Single-byte primary weights are given to particularly frequent
characters, such as space, digits, and a-z. More frequent characters
are given two-byte weights, while relatively infrequent characters
are given three-byte weights. For example:</p>
</blockquote>
<pre>...
0009; [03 05, 05, 05] # Zyyy Cc [0100.0020.0002] * &lt;CHARACTER TABULATION&gt;
...
1B60; [06 14 0C, 05, 05] # Bali Po [0111.0020.0002] * BALINESE PAMENENG
...
0031; [14, 05, 05] # Zyyy Nd [149B.0020.0002] * DIGIT ONE</pre>
<blockquote>
<p>The assignment of 2 vs 3 bytes does not reflect importance, or
exact frequency.</p>
</blockquote>
<pre>
3041; [76 06, 05, 03] # Hira Lo [3888.0020.000D] * HIRAGANA LETTER SMALL A
3042; [76 06, 05, 85] # Hira Lo [3888.0020.000E] * HIRAGANA LETTER A
30A1; [76 06, 05, 10] # Kana Lo [3888.0020.000F] * KATAKANA LETTER SMALL A
30A2; [76 06, 05, 9E] # Kana Lo [3888.0020.0011] * KATAKANA LETTER A</pre>
<blockquote>
<p>
Beginning with CLDR 27, some primary or secondary collation elements
may have below-common tertiary weights (e.g.,
<code>03</code>
), in particular to allow normal Hiragana letters to have common
tertiary weights.
</p>
</blockquote>
<pre># SPECIAL MAX/MIN COLLATION ELEMENTS
FFFE; [02, 05, 05] # Special LOWEST primary, for merge/interleaving
FFFF; [EF FE, 05, 05] # Special HIGHEST primary, for ranges</pre>
<blockquote>
<p>The two tailored noncharacters have their own primary weights.
</p>
</blockquote>
<pre>
F967; [U+4E0D] # Hani Lo [FB40.0020.0002][CE0D.0000.0000] * CJK COMPATIBILITY IDEOGRAPH-F967
2F02; [U+4E36, 10] # Hani So [FB40.0020.0004][CE36.0000.0000] * KANGXI RADICAL DOT
2E80; [U+4E36, 70, 20] # Hani So [FB40.0020.0004][CE36.0000.0000][0000.00FC.0004] * CJK RADICAL REPEAT</pre>
<blockquote>
<p>Some collation elements are specified by reference to other
mappings. This is particularly useful for Han characters which are
given implicit/constructed primary weights; the reference to a
Unified_Ideograph makes these mappings independent of implementation
details. This technique may also be used in other mappings to show
the relationship of character variants.</p>
<p>The referenced character must have a mapping listed earlier in
the file, or the mapping must have been defined via the
[Unified_Ideograph] data line. The referenced character must map to
exactly one collation element.</p>
<p>
<code>[U+4E0D]</code>
copies U+4E0D’s entire collation element.
<code>[U+4E36, 10]</code>
copies U+4E36’s primary and secondary weights and specifies a
different tertiary weight.
<code>[U+4E36, 70, 20]</code>
only copies U+4E36’s primary weight and specifies other secondary
and tertiary weights.
</p>
<p>FractionalUCA.txt does not have any explicit mappings for
implicit weights. Therefore, an implementation is free to choose an
algorithm for computing implicit weights according to the principles
specified in the UCA.</p>
</blockquote>
<pre>
FDD1 20AC; [0D 20 02, 05, 05] # CURRENCY first primary
FDD1 0034; [0E 02 02, 05, 05] # DIGIT first primary starts new lead byte
FDD0 FF21; [26 02 02, 05, 05] # REORDER_RESERVED_BEFORE_LATIN first primary starts new lead byte
FDD1 004C; [28 02 02, 05, 05] # LATIN first primary starts new lead byte
FDD0 FF3A; [5D 02 02, 05, 05] # REORDER_RESERVED_AFTER_LATIN first primary starts new lead byte
FDD1 03A9; [5F 04 02, 05, 05] # GREEK first primary starts new lead byte (compressible)
FDD1 03E2; [5F 60 02, 05, 05] # COPTIC first primary (compressible)</pre>
<blockquote>
<p>
These are special mappings with primaries at the boundaries of
scripts and reordering groups. They serve as tailoring boundaries,
so that tailoring near the first or last character of a script or
group places the tailored item into the same group. Beginning with
CLDR 24, each of these is a contraction of U+FDD1 with
a character of the corresponding script
(or of the General_Category [Z, P, S, Sc, Nd]
corresponding to a special reordering group),
mapping to the first possible primary weight per
script or group. They can be enumerated for implementations of <a
href="#Collation_Indexes">Collation Indexes</a>. (Earlier versions
mapped contractions with U+FDD0 to the last primary weights of each
group but not each script.)
</p>
<p>Beginning with CLDR 27, these mappings alone define the
boundaries for reordering single scripts. (There are no mappings for
Hrkt, Hans, or Hant because they are not fully distinct scripts;
they share primary weights with other scripts: Hrkt=Hira=Kana &amp;
Hans=Hant=Hani.) There are some reserved ranges, beginning at
boundaries marked with U+FDD0 plus following characters as shown
above. The reserved ranges are not used for collation elements and
are not available for tailoring.</p>
<p>Some primary lead bytes must be reserved so that reordering of
scripts along partial-lead-byte boundaries can “split” the primary
lead byte and use up a reserved byte. This is for implementations
that write sort keys, which must reorder primary weights by
offsetting them by whole lead bytes. There are reorder-reserved
ranges before and after Latin, so that reordering scripts with few
primary lead bytes relative to Latin can move those scripts into the
reserved ranges without changing the primary weights of any other
script. Each of these boundaries begins with a new two-byte primary;
that is, no two groups/scripts/ranges share the top 16 bits of their
primary weights.</p>
</blockquote>
<pre>
FDD0 0034; [11, 05, 05] # lead byte for numeric sorting</pre>
<blockquote>
<p>This mapping specifies the lead byte for numeric sorting. It
must be different from the lead byte of any other primary weight,
otherwise numeric sorting would generate ill-formed collation
elements. Therefore, this mapping itself must be excluded from the
set of regular mappings. This value can be ignored by
implementations that do not support numeric sorting. (Other
contractions with U+FDD0 can normally be ignored altogether.)</p>
</blockquote>
<pre>
# HOMELESS COLLATION ELEMENTS
FDD0 0063; [, 97, 3D] # [15E4.0020.0004] [1844.0020.0004] [0000.0041.001F] * U+01C6 LATIN SMALL LETTER DZ WITH CARON
FDD0 0064; [, A7, 09] # [15D1.0020.0004] [0000.0056.0004] * U+1DD7 COMBINING LATIN SMALL LETTER C CEDILLA
FDD0 0065; [, B1, 09] # [1644.0020.0004] [0000.0061.0004] * U+A7A1 LATIN SMALL LETTER G WITH OBLIQUE STROKE</pre>
<blockquote>
<p>The DUCET has some weights that don't correspond directly to a
character. To allow for implementations to have a mapping for each
collation element (necessary for certain implementations of
tailoring), this requires the construction of special sequences for
those weights. These collation elements can normally be ignored.</p>
</blockquote>
<p>Next, a number of tables are defined. The function of each of
the tables is summarized afterwards.</p>
<pre># VALUES BASED ON UCA
...
[first regular [0D 0A, 05, 05]] # U+0060 GRAVE ACCENT
[last regular [7A FE, 05, 05]] # U+1342E EGYPTIAN HIEROGLYPH AA032
[first implicit [E0 04 06, 05, 05]] # CONSTRUCTED
[last implicit [E4 DF 7E 20, 05, 05]] # CONSTRUCTED
[first trailing [E5, 05, 05]] # CONSTRUCTED
[last trailing [E5, 05, 05]] # CONSTRUCTED
...</pre>
<blockquote>
<p>This table summarizes ranges of important groups of characters
for implementations.</p>
</blockquote>
<pre># Top Byte =&gt; Reordering Tokens
[top_byte 00 TERMINATOR ] # [0] TERMINATOR=1
[top_byte 01 LEVEL-SEPARATOR ] # [0] LEVEL-SEPARATOR=1
[top_byte 02 FIELD-SEPARATOR ] # [0] FIELD-SEPARATOR=1
[top_byte 03 SPACE ] # [9] SPACE=1 Cc=6 Zl=1 Zp=1 Zs=1
...</pre>
<blockquote>
<p>This table defines the reordering groups, for script
reordering. The table maps from the first bytes of the fractional
weights to a reordering token. The format is &quot;[top_byte &quot;
byte-value reordering-token &quot;COMPRESS&quot;? &quot;]&quot;. The
&quot;COMPRESS&quot; value is present when there is only one byte in
the reordering token, and primary-weight compression can be applied.
Most reordering tokens are script values; others are special-purpose
values, such as PUNCTUATION. Beginning with CLDR 24, this table
precedes the regular mappings, so that parsers can use this
information while processing and optimizing mappings. Beginning with
CLDR 27, most of this data is irrelevant because single scripts can
be reordered. Only the "COMPRESS" data is still useful.</p>
</blockquote>
<pre># Reordering Tokens =&gt; Top Bytes
[reorderingTokens Arab 61=910 62=910 ]
[reorderingTokens Armi 7A=22 ]
[reorderingTokens Armn 5F=82 ]
[reorderingTokens Avst 7A=54 ]
...</pre>
<blockquote>
<p>This table is an inverse mapping from reordering token to top
byte(s). In terms like &quot;61=910&quot;, the first value is the
top byte, while the second is informational, indicating the number
of primaries assigned with that top byte.</p>
</blockquote>
<pre># General Categories =&gt; Top Byte
[categories Cc 03{SPACE}=6 ]
[categories Cf 77{Khmr Tale Talu Lana Cham Bali Java Mong Olck Cher Cans Ogam Runr Orkh Vaii Bamu}=2 ]
[categories Lm 0D{SYMBOL}=25 0E{SYMBOL}=22 27{Latn}=12 28{Latn}=12 29{Latn}=12 2A{Latn}=12...</pre>
<blockquote>
<p>This table is informational, providing the top bytes, scripts,
and primaries associated with each general category value.</p>
</blockquote>
<pre># FIXED VALUES
[fixed first implicit byte E0]
[fixed last implicit byte E4]
[fixed first trail byte E5]
[fixed last trail byte EF]
[fixed first special byte F0]
[fixed last special byte FF]
[fixed secondary common byte 05]
[fixed last secondary common byte 45]
[fixed first ignorable secondary byte 80]
[fixed tertiary common byte 05]
[fixed first ignorable tertiary byte 3C]
</pre>
<blockquote>
<p>The final table gives certain hard-coded byte values. The
&quot;trail&quot; area is provided for implementation of the
&quot;trailing weights&quot; as described in the UCA.</p>
</blockquote>
<p class="note">Note: The particular primary lead bytes for Hani
vs. IMPLICIT vs. TRAILING are only an example. An implementation is
free to move them if it also moves the explicit TRAILING weights.
This affects only a small number of explicit mappings in
FractionalUCA.txt, such as for U+FFFD, U+FFFF, and the “unassigned
first primary”. It is possible to use no SPECIAL bytes at all, and to
use only the one primary lead byte FF for TRAILING weights.</p>
<h4>
2.6.3 <a name="File_Format_UCA_Rules_txt"
href="#File_Format_UCA_Rules_txt">UCA_Rules.txt</a>
</h4>
<p>
The format for this file uses the CLDR collation syntax, see <i>Section
3, <a href="#Collation_Tailorings">Collation Tailorings</a>
</i>.
</p>
<h2>
3 <a name="Collation_Tailorings" href="#Collation_Tailorings">Collation
Tailorings</a>
</h2>
<p class="dtd">&lt;!ELEMENT collations (alias |
(defaultCollation?, collation*, special*)) &gt;</p>
<p class="dtd">&lt;!ELEMENT defaultCollation ( #PCDATA ) &gt;</p>
<p>
This element of the LDML format contains one or more <span
class="element">collation</span> elements, distinguished by type.
Each <span class="element">collation</span> contains elements with
parametric settings, or rules that specify a certain sort order, as a
tailoring of the root order, or both.
</p>
<p class="note">
Note: CLDR collation tailoring data should follow the <a
href="http://cldr.unicode.org/index/cldr-spec/collation-guidelines">CLDR
Collation Guidelines</a>.
</p>
<h3>
3.1 <a name="Collation_Types" href="#Collation_Types">Collation
Types</a>
</h3>
<p>
Each locale may have multiple sort orders (types). The <span
class="element">defaultCollation</span> element defines the default
tailoring for a locale and its sublocales. For example:
</p>
<ul>
<li>root.xml: <code>&lt;defaultCollation&gt;standard&lt;/defaultCollation&gt;</code></li>
<li>zh.xml: <code>&lt;defaultCollation&gt;pinyin&lt;/defaultCollation&gt;</code></li>
<li>zh_Hant.xml: <code>&lt;defaultCollation&gt;stroke&lt;/defaultCollation&gt;</code></li>
</ul>
<p>
To allow implementations in reduced memory environments to use CJK
sorting, there are also short forms of each of these collation
sequences. These provide for the most common characters in common
use, and are marked with <span class="attribute">alt</span>=&quot;<span
class="attributeValue">short</span>&quot;.
</p>
<p>A collation type name that starts with "private-", for example,
"private-kana", indicates an incomplete tailoring that is only
intended for import into one or more other tailorings (usually for
sharing common rules). It does not establish a complete sort order.
An implementation should not build data tables for a private
collation type, and should not include a private collation type in a
list of available types.</p>
<p class="note">
<b>Note:</b>
</p>
<ul>
<li>There is an on-line demonstration of collation at [<a
href="tr35.html#LocaleExplorer">LocaleExplorer</a>] that uses the
same rule syntax. (Pick the locale and scroll to &quot;Collation
Rules&quot;, near the end.)
</li>
<li class="note">In CLDR 23 and before, LDML collation files
used an XML format. Starting with CLDR 24, the XML collation syntax
is deprecated and no longer used. See the <i><a
href="http://www.unicode.org/reports/tr35/tr35-31/tr35-collation.html#Collation_Tailorings">CLDR
23 version of this document</a></i> for details about the XML collation
syntax.
</li>
</ul>
<h4>
3.1.1 <a name="Collation_Type_Fallback"
href="#Collation_Type_Fallback">Collation Type Fallback</a>
</h4>
<p>When loading a requested tailoring from its data file and the
parent file chain, use the following type fallback to find the
tailoring.</p>
<ol>
<li>Determine the default type from the &lt;defaultCollation&gt;
element; map the default type to its alias if one is defined. If
there is no &lt;defaultCollation&gt; element, then use "standard" as
the default type.</li>
<li>If the request language tag specifies the collation type
(keyword "co"), then map it to its alias if one is defined (e.g.,
"-co-phonebk" → "phonebook"). If the language tag does not specify
the type, then use the default type.</li>
<li>Use the &lt;collation&gt; element with this type.</li>
<li>If it does not exist, and the type starts with "search" but
is longer, then set the type to "search" and use that
&lt;collation&gt; element. (For example, "searchjl" → "search".)</li>
<li>If it does not exist, and the type is not the default type,
then set the type to the default type and use that &lt;collation&gt;
element.</li>
<li>If it does not exist, and the type is not "standard", then
set the type to "standard" and use that &lt;collation&gt; element.</li>
<li>If it does not exist, then use the CLDR root collation.</li>
</ol>
<p class="note">Note that the CLDR collation/root.xml contains
&lt;defaultCollation&gt;standard&lt;/defaultCollation&gt;,
&lt;collation type="standard"&gt; (with an empty tailoring, so this
is the same as the CLDR root collation), and &lt;collation
type="search"&gt;.</p>
<p>For example, assume that we have collation data for the
following tailorings. ("da/search" is shorthand for
"da-u-co-search".)</p>
<ul>
<li>root/defaultCollation=standard</li>
<li>root/standard (this is the same as “the CLDR root collator”)</li>
<li>root/search</li>
<li>da/standard</li>
<li>da/search</li>
<li>el/standard</li>
<li>ko/standard</li>
<li>ko/search</li>
<li>ko/searchjl</li>
<li>zh/defaultCollation=pinyin</li>
<li>zh/pinyin</li>
<li>zh/stroke</li>
<li>zh-Hant/defaultCollation=stroke</li>
</ul>
<table>
<caption>
<a name="Sample_requested_and_actual_collation_locales_and_types"
href="#Sample_requested_and_actual_collation_locales_and_types">Sample
requested and actual collation locales and types</a>
</caption>
<tr>
<th>requested</th>
<th>actual</th>
<th>comment</th>
</tr>
<tr>
<td>da/phonebook</td>
<td>da/standard</td>
<td>default type for Danish</td>
</tr>
<tr>
<td>zh</td>
<td>zh/pinyin</td>
<td>default type for zh</td>
</tr>
<tr>
<td>zh/standard</td>
<td>root/standard</td>
<td>no "standard" tailoring for zh, falls back to root</td>
</tr>
<tr>
<td>zh/phonebook</td>
<td>zh/pinyin</td>
<td>default type for zh</td>
</tr>
<tr>
<td>zh-Hant/phonebook</td>
<td>zh/stroke</td>
<td>default type for zh-Hant is "stroke"</td>
</tr>
<tr>
<td>da/searchjl</td>
<td>da/search</td>
<td>"search.+" falls back to "search"</td>
</tr>
<tr>
<td>el/search</td>
<td>root/search</td>
<td>no "search" tailoring for Greek</td>
</tr>
<tr>
<td>el/searchjl</td>
<td>root/search</td>
<td>"search.+" falls back to "search", found in root</td>
</tr>
<tr>
<td>ko/searchjl</td>
<td>ko/searchjl</td>
<td>requested data is actually available</td>
</tr>
</table>
<h3>
3.2 <a name="Collation_Version" href="#Collation_Version">Version</a>
</h3>
<p>The version attribute is used in case a specific version of the
UCA is to be specified. It is optional, and is specified if the
results are to be identical on different systems. If it is not
supplied, then the version is assumed to be the same as the Unicode
version for the system as a whole.</p>
<blockquote>
<p class="note">
<b>Note: </b>For version 3.1.1 of the UCA, the version of Unicode
must also be specified with any versioning information; an example
would be &quot;3.1.1/3.2&quot; for version 3.1.1 of the UCA, for
version 3.2 of Unicode. This was changed by decision of the UTC, so
that dual versions were no longer necessary. So for UCA 4.0 and
beyond, the version just has a single number.
</p>
</blockquote>
<h3>
3.3 <a name="Collation_Element" href="#Collation_Element">Collation
Element</a>
</h3>
<p class="dtd">&lt;!ELEMENT collation (alias | (cr*, special*))
&gt;</p>
<p>
The tailoring syntax is designed to be independent of the actual
weights used in any particular UCA table. That way the same rules can
be applied to UCA versions over time, even if the underlying weights
change. The following illustrates the overall structure of a <span
class="element">collation</span>:
</p>
<pre>&lt;collation type="phonebook"&gt;
&lt;cr&gt;&lt;![CDATA[
[caseLevel on]
&amp;c &lt; k
]]&gt;&lt;/cr&gt;
&lt;/collation&gt;</pre>
<h3>
3.4 <a name="Setting_Options" href="#Setting_Options">Setting
Options</a>
</h3>
<p>
Parametric settings can be specified in language tags or in rule
syntax (in the form
<code>[keyword value]</code>
). For example,
<code>-ks-level2</code>
or
<code>[strength 2]</code>
will only compare strings based on their primary and secondary
weights.
</p>
<p>
If a setting is not present, the CLDR default (or the default for the
locale, if there is one) is used. That default is listed in bold
italics. Where there is a UCA default that is different, it is listed
in bold with (<strong>UCA default</strong>). Note that the default
value for a locale may be different than the normal default value for
the setting.
</p>
<table>
<caption>
<a name="Collation_Settings" href="#Collation_Settings">Collation
Settings</a>
</caption>
<tr>
<th>BCP47 Key</th>
<th>BCP47 Value</th>
<th>Rule Syntax</th>
<th>Description</th>
</tr>
<tr>
<td rowspan="5">ks</td>
<td>level1</td>
<td><code>[strength 1]</code><br>(primary)</td>
<td rowspan="5">Sets the default strength for comparison, as
described in the [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>].<em>
Note that a strength setting of greater than 4 may have the same
effect as <strong>identical</strong>, depending on the locale and
implementation.
</em>
</td>
</tr>
<tr>
<td>level2</td>
<td><code>[strength 2]</code><br>(secondary)</td>
</tr>
<tr>
<td>level3</td>
<td><em><strong><code>[strength 3]</code><br>(tertiary)</strong></em></td>
</tr>
<tr>
<td>level4</td>
<td><code>[strength 4]</code><br>(quaternary)</td>
</tr>
<tr>
<td>identic</td>
<td><code>[strength I]</code><br>(identical)</td>
</tr>
<tr>
<td rowspan="3">ka</td>
<td>noignore</td>
<td><i><strong><code>[alternate
non-ignorable]</code></strong></i><br></td>
<td rowspan="3">Sets alternate handling for variable weights,
as described in [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>], where
&quot;shifted&quot; causes certain characters to be ignored in
comparison. <em>The default for LDML is different than it is
in the UCA. In LDML, the default for alternate handling is <strong>non-ignorable</strong>,
while in UCA it is <strong>shifted</strong>. In addition, in LDML
only whitespace and punctuation are variable by default.
</em>
</td>
</tr>
<tr>
<td>shifted</td>
<td><strong><code>[alternate shifted]</code><br>(UCA
default)</strong></td>
</tr>
<tr>
<td><em>n/a</em></td>
<td><i>n/a</i><br>(blanked)</td>
</tr>
<tr>
<td rowspan="2">kb</td>
<td>true</td>
<td><code>[backwards 2]</code></td>
<td rowspan="2">Sets the comparison for the second level to be
<strong>backwards</strong>, as described in [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>].
</td>
</tr>
<tr>
<td>false</td>
<td><i><strong>n/a</strong></i></td>
</tr>
<tr>
<td rowspan="2">kk</td>
<td>true</td>
<td><strong><code>[normalization on]</code><br>(UCA
default)</strong></td>
<td rowspan="2">If <strong>on</strong>, then the normal [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>]
algorithm is used. If <strong>off</strong>, then most strings
should still sort correctly despite not normalizing to NFD first.<br>
<em>Note that the default for CLDR locales may be different
than in the UCA. The rules for particular locales have it set to <strong>on</strong>:
those locales whose exemplar characters (in forms commonly
interchanged) would be affected by normalization.
</em>
</td>
</tr>
<tr>
<td>false</td>
<td><i><strong><code>[normalization off]</code></strong></i></td>
</tr>
<tr>
<td rowspan="2">kc</td>
<td>true</td>
<td><code>[caseLevel on]</code></td>
<td rowspan="2">If set to <strong>on</strong><i>,</i> a level
consisting only of case characteristics will be inserted in front
of tertiary level, as a &quot;Level 2.5&quot;. To ignore accents
but take case into account, set strength to <strong>primary</strong>
and case level to <strong>on</strong>. For details, see <em>Section
3.14, <a href="#Case_Parameters">Case Parameters</a>
</em>.
</td>
</tr>
<tr>
<td>false</td>
<td><i><strong><code>[caseLevel off]</code></strong></i></td>
</tr>
<tr>
<td rowspan="3">kf</td>
<td>upper</td>
<td><code>[caseFirst upper]</code></td>
<td rowspan="3">If set to <strong>upper</strong>, causes upper
case to sort before lower case. If set to <strong>lower</strong>,
causes lower case to sort before upper case. Useful for locales
that have already supported ordering but require different order of
cases. Affects case and tertiary levels. For details, see <em>Section
3.14, <a href="#Case_Parameters">Case Parameters</a>
</em>.
</td>
</tr>
<tr>
<td>lower</td>
<td><code>[caseFirst lower]</code></td>
</tr>
<tr>
<td>false</td>
<td><i><strong><code>[caseFirst off]</code></strong></i></td>
</tr>
<tr>
<td rowspan="2">kh</td>
<td>true<br> <i><strong>Deprecated:</strong></i> Use rules
with quater&shy;nary relations instead.
</td>
<td><code>[hiraganaQ on]</code></td>
<td rowspan="2">Controls special treatment of Hiragana code
points on quaternary level. If turned <strong>on</strong>, Hiragana
codepoints will get lower values than all the other non-variable
code points in <strong>shifted</strong>. That is, the normal Level
4 value for a regular collation element is FFFF, as described in [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>], <em>Section
3.6, <a
href="http://www.unicode.org/reports/tr10/#Variable_Weighting">Variable
Weighting</a>
</em>. This is changed to FFFE for [:script=Hiragana:] characters. The
strength must be greater or equal than quaternary if this attribute
is to have any effect.
</td>
</tr>
<tr>
<td>false</td>
<td><i><strong><code>[hiraganaQ off]</code></strong></i></td>
</tr>
<tr>
<td rowspan="2">kn</td>
<td>true</td>
<td><code>[numericOrdering on]</code></td>
<td rowspan="2">If set to <strong>on</strong>, any sequence of
Decimal Digits (General_Category = Nd in the [<a
href="http://www.unicode.org/reports/tr41/#UAX44">UAX44</a>]) is
sorted at a primary level with its numeric value. For example,
&quot;A-21&quot; &lt; &quot;A-123&quot;. The computed primary
weights are all at the start of the <strong>digit</strong>
reordering group. Thus with an untailored UCA table, &quot;a$&quot;
&lt; &quot;a0&quot; &lt; &quot;a2&quot; &lt; &quot;a12&quot; &lt;
&quot;a⓪&quot; &lt; &quot;aa&quot;.
</td>
</tr>
<tr>
<td>false</td>
<td><i><strong><code>[numericOrdering off]</code></strong></i></td>
</tr>
<tr>
<td>kr</td>
<td>a sequence of one or more reorder codes: <strong>space,
punct, symbol, currency, digit</strong>, or any BCP47 script ID
</td>
<td><code>[reorder Grek digit]</code></td>
<td>Specifies a reordering of scripts or other significant
blocks of characters such as symbols, punctuation, and digits. For
the precise meaning and usage of the reorder codes, see <em>Section
3.13, <a href="#Script_Reordering">Collation Reordering</a>.
</em>
</td>
</tr>
<tr>
<td rowspan="4">kv</td>
<td>space</td>
<td><code>[maxVariable space]</code></td>
<td rowspan="4">Sets the variable top to the top of the
specified reordering group. All code points with primary weights
less than or equal to the variable top will be considered variable,
and thus affected by the alternate handling. Variables are
ignorable by default in [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>], but not
in CLDR.
</td>
</tr>
<tr>
<td>punct</td>
<td><i><strong><code>[maxVariable punct]</code></strong></i></td>
</tr>
<tr>
<td>symbol</td>
<td><strong><code>[maxVariable symbol]</code><br>(UCA
default)</strong></td>
</tr>
<tr>
<td>currency</td>
<td><code>[maxVariable currency]</code></td>
</tr>
<tr>
<td>vt</td>
<td>See <i>Part 1 Section 3.6.4, <a
href="tr35.html#Unicode_Locale_Extension_Data_Files">U
Extension Data Files</a></i>.<br> <i><strong>Deprecated:</strong></i>
Use maxVariable instead.
</td>
<td><code>&amp;\u00XX\uYYYY &lt; [variable top]</code><br>
<br> (the default is set to the highest punctuation, thus
including spaces and punctuation, but not symbols)</td>
<td>
<p>
The BCP47 value is described in <i>Appendix Q: <a
href="tr35.html#Locale_Extension_Key_and_Type_Data">Locale
Extension Keys and Types</a>.
</i>
</p>
<p>
Sets the string value for the variable top. All the code points
with primary weights less than or equal to the variable top will
be considered variable, and thus affected by the alternate
handling.<br> An implementation that supports the variableTop
setting should also support the maxVariable setting, and it should
"pin" ("round up") the variableTop to the top of the containing
reordering group.<br> Variables are ignorable by default in [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>], but
not in CLDR. See below for more information.
</p>
</td>
</tr>
<tr>
<td><em>n/a</em></td>
<td><em>n/a</em></td>
<td><em>n/a</em></td>
<td>match-boundaries: <em><strong>none</strong></em> |
whole-character | whole-word <br> Defined by <em>Section
8, <a href="http://www.unicode.org/reports/tr10/#Searching">Searching
and Matching</a>
</em> of [<a href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>].
</td>
</tr>
<tr>
<td><em>n/a</em></td>
<td><em>n/a</em></td>
<td><em>n/a</em></td>
<td>match-style: <em><strong>minimal</strong></em> | medial |
maximal <br> Defined by <em>Section 8, <a
href="http://www.unicode.org/reports/tr10/#Searching">Searching
and Matching</a></em> of [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>].
</td>
</tr>
</table>
<h4>
3.4.1 <a name="Common_Settings" href="#Common_Settings">Common
settings combinations</a>
</h4>
<p>Some commonly used parametric collation settings are available
via combinations of LDML settings attributes:</p>
<ul>
<li>“Ignore accents”: <strong>strength=primary</strong></li>
<li>“Ignore accents” but take case into account: <strong>strength=primary
caseLevel=on</strong></li>
<li>“Ignore case”: <strong>strength=secondary</strong></li>
<li>“Ignore punctuation” (completely): <strong>strength=tertiary
alternate=shifted</strong></li>
<li>“Ignore punctuation” but distinguish among punctuation
marks: <strong>strength=quaternary alternate=shifted</strong>
</li>
</ul>
<h4>
3.4.2 <a name="Normalization_Setting" href="#Normalization_Setting">Notes
on the normalization setting</a>
</h4>
<p>The UCA always normalizes input strings into NFD form before
the rest of the algorithm. However, this results in poor performance.</p>
<p>
With <strong>normalization=off</strong>, strings that are in [<a
href="tr35.html#FCD">FCD</a>] and do not contain Tibetan precomposed
vowels (U+0F73, U+0F75, U+0F81) should sort correctly. With <strong>normalization=on</strong>,
an implementation that does not normalize to NFD must at least
perform an incremental FCD check and normalize substrings as
necessary. It should also always decompose the Tibetan precomposed
vowels. (Otherwise discontiguous contractions across their leading
components cannot be handled correctly.)
</p>
<p>Another complication for an implementation that does not always
use NFD arises when contraction mappings overlap with canonical
Decomposition_Mapping strings. For example, the Danish contraction
“aa” overlaps with the decompositions of ‘ä’, ‘å’, and other
characters. In the root collation (and in the DUCET), Cyrillic ‘ӛ’
maps to a single collation element, which means that its
decomposition “ә+&#x25CC;&#x0308;” forms a contraction, and its
second character (U+0308) is the same as the first character in the
Decomposition_Mapping of U+0344
‘&#x25CC;&#x0344;’=“&#x25CC;&#x0308;+&#x25CC;&#x0301;”.</p>
<p>In order to handle strings with these characters (e.g., “aä”
and “ә&#x0344;” [which are in FCD]) exactly as with prior NFD
normalization, an implementation needs to either add overlap
contractions to its data (e.g., “a+ä” and “ә+&#x25CC;&#x0344;”), or
it needs to decompose the relevant composites (e.g., ‘ä’ and
‘&#x25CC;&#x0344;’) as soon as they are encountered.</p>
<h4>
3.4.3 <a name="Variable_Top_Settings" href="#Variable_Top_Settings">Notes
on variable top settings</a>
</h4>
<p>
Users may want to include more or fewer characters as Variable. For
example, someone could want to restrict the Variable characters to
just include space marks. In that case, maxVariable would be set to
"space". (In CLDR 24 and earlier, the now-deprecated variableTop
would be set to U+1680, see the “Whitespace” <a
href="http://unicode.org/charts/collation/">UCA collation chart</a>).
Alternatively, someone could want more of the Common characters in
them, and include characters up to (but not including) '0', by
setting maxVariable to "currency". (In CLDR 24 and earlier, the
now-deprecated variableTop would be set to U+20BA, see the
“Currency-Symbol” collation chart).
</p>
<p>The effect of these settings is to customize to ignore
different sets of characters when comparing strings. For example, the
locale identifier "de-u-ka-shifted-kv-currency" is requesting
settings appropriate for German, including German sorting
conventions, and that currency symbols and characters sorting below
them are ignored in sorting.</p>
<h3>
3.5 <a name="Rules" href="#Rules">Collation Rule Syntax</a>
</h3>
<p class="dtd">&lt;!ELEMENT cr #PCDATA &gt;</p>
<p>
The goal for the collation rule syntax is to have clearly expressed
rules with a concise format. The CLDR rule syntax is a subset of the
[<a href="tr35.html#ICUCollation">ICUCollation</a>] syntax.
</p>
<p>
For the CLDR root collation, the FractionalUCA.txt file defines all
mappings for all of Unicode directly, and it also provides
information about script boundaries, reordering groups, and other
details. For tailorings, this is neither necessary nor practical. In
particular, while the root collation sort order rarely changes for
existing characters, their numeric collation weights change with
every version. If tailorings also specified numeric weights directly,
then they would have to change with every version, parallel with the
root collation. Instead, for tailorings, mappings are added and
modified relative to the root collation. (There is no syntax to <i>remove</i>
mappings, except via <a href="#Special_Purpose_Commands">special
[suppressContractions [...]] </a>.)
</p>
<p>
The ASCII [:P:] and [:S:] characters are reserved for collation
syntax:
<code>[\u0021-\u002F \u003A-\u0040 \u005B-\u0060
\u007B-\u007E]</code>
</p>
<p>Unicode Pattern_White_Space characters between tokens are
ignored. Unquoted white space terminates reset and relation strings.</p>
<p>A pair of ASCII apostrophes encloses quoted literal text. They
are normally used to enclose a syntax character or white space, or a
whole reset/relation string containing one or more such characters,
so that those are parsed as part of the reset/relation strings rather
than treated as syntax. A pair of immediately adjacent apostrophes is
used to encode one apostrophe.</p>
<p>
Code points can be escaped with
<code>\uhhhh</code>
and
<code>\U00hhhhhh</code>
escapes, as well as common escapes like
<code>\t</code>
and
<code>\n</code>
. (For details see the documentation of ICU
UnicodeString::unescape().) This is particularly useful for
default-ignorable code points, combining marks, visually indistinct
variants, hard-to-type characters, etc. These sequences are unescaped
before the rules are parsed; this means that even escaped syntax and
white space characters need to be enclosed in apostrophes. For
example:
<code>&amp;'\u0020'='\u3000'</code>
</p>
<p>
The ASCII double quote must be both escaped (so that the collation
syntax can be enclosed in pairs of double quotes in programming
environments) and quoted. For example:
<code>&amp;'\u0022'&lt;&lt;&lt;x</code>
</p>
<p>
Comments are allowed at the beginning, and after any complete reset,
relation, setting, or command. A comment begins with a
<code>#</code>
and extends to the end of the line (according to the Unicode Newline
Guidelines).
</p>
<p>The collation syntax is case-sensitive.</p>
<h3>
3.6 <a name="Orderings" href="#Orderings">Orderings</a>
</h3>
<p>The root collation mappings form the initial state. Mappings
are added and removed via a sequence of rule chains. Each tailoring
rule builds on the current state after all of the preceding rules
(and is not affected by any following rules). Rule chains may
alternate with comments, settings, and special commands.</p>
<p>A rule chain consists of a reset followed by one or more
relations. The reset position is a string which maps to one or more
collation elements according to the current state. A relation
consists of an operator and a string; it maps the string to the
current collation elements, modified according to the operator.</p>
<table>
<caption>
<a name="Specifying_Collation_Ordering"
href="#Specifying_Collation_Ordering">Specifying Collation
Ordering</a>
</caption>
<tr>
<th>Relation Operator</th>
<th>&nbsp;Example</th>
<th>Description</th>
</tr>
<tr>
<td><code>&amp;</code></td>
<td><code>&amp; Z</code></td>
<td>Map Z to collation elements according to the current state.
These will be modified according to the following relation
operators and then assigned to the corresponding relation strings.</td>
</tr>
<tr>
<td><code>&lt;</code></td>
<td><code>
&amp; a<br> &lt; b
</code></td>
<td>Make &#39;b&#39; sort after &#39;a&#39;, as a <i>primary</i>
(base-character) difference
</td>
</tr>
<tr>
<td><code>&lt;&lt;</code></td>
<td><code>
&amp; a<br> &lt;&lt; ä
</code></td>
<td>Make &#39;ä&#39; sort after &#39;a&#39; as a <i>secondary</i>
(accent) difference
</td>
</tr>
<tr>
<td><code>&lt;&lt;&lt;</code></td>
<td><code>
&amp; a<br> &lt;&lt;&lt; A
</code></td>
<td>Make &#39;A&#39; sort after &#39;a&#39; as a <i>tertiary</i>
(case/variant) difference
</td>
</tr>
<tr>
<td><code>&lt;&lt;&lt;&lt;</code></td>
<td><code>
&amp; か<br> &lt;&lt;&lt;&lt; カ
</code></td>
<td>Make &#39;カ&#39; (Katakana Ka) sort after &#39;か&#39;
(Hiragana Ka) as a <i>quaternary</i> difference
</td>
</tr>
<tr>
<td><code>=&nbsp; </code></td>
<td><code>
&amp; v<br> = w&nbsp;
</code></td>
<td>Make &#39;w&#39; sort <i>identically</i> to &#39;v&#39;
</td>
</tr>
</table>
<p>The following shows the result of serially applying three
rules.</p>
<table>
<tr>
<th>&nbsp;</th>
<th>Rules</th>
<th>Result</th>
<th>Comment</th>
</tr>
<tr>
<td>1</td>
<td>&amp; a &lt; g</td>
<td>... a<font color="red"> &lt;<sub>1</sub> g
</font> ...
</td>
<td>Put g after a.</td>
</tr>
<tr>
<td>2</td>
<td>&amp; a &lt; h &lt; k</td>
<td>... a<font color="red"> &lt;<sub>1</sub> h &lt;<sub>1</sub>
k
</font> &lt;<sub>1</sub> g ...
</td>
<td>Now put h and k after a (inserting before the g).</td>
</tr>
<tr>
<td>3</td>
<td>&amp; h &lt;&lt; g</td>
<td>... a &lt;<sub>1</sub> h<font color="red"> &lt;<sub>1</sub>
g
</font> &lt;<sub>1</sub> k ...
</td>
<td>Now put g after h (inserting before k).</td>
</tr>
</table>
<p>Notice that relation strings can occur multiple times, and thus
override previous rules.</p>
<p>Each relation uses and modifies the collation elements of the
immediately preceding reset position or relation. A rule chain with
two or more relations is equivalent to a sequence of “atomic rules”
where each rule chain has exactly one relation, and each relation is
followed by a reset to this same relation string.</p>
<p>
<i>Example:</i>
</p>
<table>
<tr>
<th>Rules</th>
<th>Equivalent Atomic Rules</th>
</tr>
<tr>
<td>&amp; b &lt; q &lt;&lt;&lt; Q<br> &amp; a &lt; x
&lt;&lt;&lt; X &lt;&lt; q &lt;&lt;&lt; Q &lt; z
</td>
<td>&amp; b &lt; q<br> &amp; q &lt;&lt;&lt; Q<br>
&amp; a &lt; x<br> &amp; x &lt;&lt;&lt; X<br> &amp; X
&lt;&lt; q<br> &amp; q &lt;&lt;&lt; Q<br> &amp; Q &lt; z
</td>
</tr>
</table>
<p>This is not always possible because prefix and extension
strings can occur in a relation but not in a reset (see below).</p>
<p>
The relation operator
<code>=</code>
maps its relation string to the current collation elements. Any other
relation operator modifies the current collation elements as follows.
</p>
<ul>
<li>Find the <i>last</i> collation element whose strength is at
least as great as the strength of the operator. For example, for <code>&lt;&lt;</code>
find the last primary or secondary CE. This CE will be modified; all
following CEs should be removed. If there is no such CE, then reset
the collation elements to a single completely-ignorable CE.
</li>
<li>Increment the collation element weight corresponding to the
strength of the operator. For example, for <code>&lt;&lt;</code>
increment the secondary weight.
</li>
<li>The new weight must be less than the next weight for the
same combination of higher-level weights of any collation element
according to the current state.</li>
<li>Weights must be allocated in accordance with the <a
href="http://www.unicode.org/reports/tr10/#Well-Formed">UCA
well-formedness conditions</a>.
</li>
<li>When incrementing any weight, lower-level weights should be
reset to the “common” values, to help with sort key compression.</li>
</ul>
<p>
In all cases, even for
<code>=</code>
, the case bits are recomputed according to <i>Section 3.13, <a
href="#Case_Parameters">Case Parameters</a></i>. (This can be skipped if
an implementation does not support the caseLevel or caseFirst
settings.)
</p>
<p>
For example,
<code>&amp;ae&lt;x</code>
maps ‘x’ to two collation elements. The first one is the same as for
‘a’, and the second one has a primary weight between those for ‘e’
and ‘f’. As a result, ‘x’ sorts between “ae” and “af”. (If the
primary of the first collation element was incremented instead, then
‘x’ would sort after “az”. While also sorting primary-after “ae” this
would be surprising and sub-optimal.)
</p>
<p>Some additional operators are provided to save space with large
tailorings. The addition of a * to the relation operator indicates
that each of the following single characters are to be handled as if
they were separate relations with the corresponding strength. Each of
the following single characters must be NFD-inert, that is, it does
not have a canonical decomposition and it does not reorder (ccc=0).
This keeps abbreviated rules unambiguous.</p>
<p>
A starred relation operator is followed by a sequence of characters
with the same quoting/escaping rules as normal relation strings. Such
a sequence can also be followed by one or more pairs of ‘-’ and
another sequence of characters. The single characters adjacent to the
‘-’ establish a code point order range. The same character cannot be
both the end of a range and the start of another range. (For example,
<code>&lt;a-d-g</code>
is not allowed.)
</p>
<table>
<caption>
<a name="Abbreviating_Ordering_Specifications"
href="#Abbreviating_Ordering_Specifications">Abbreviating
Ordering Specifications</a>
</caption>
<tr>
<th>Relation Operator</th>
<th>Example</th>
<th>Equivalent</th>
</tr>
<tr>
<td><code>&lt;*</code></td>
<td><code>
&amp; <span style="color: blue">a</span><br> &lt;* <span
style="color: blue">bcd-gp-s</span>&nbsp;
</code></td>
<td><code>
&amp; <span style="color: blue">a</span><br> &lt; <span
style="color: blue">b </span>&lt;<span style="color: blue">
c </span>&lt;<span style="color: blue"> d</span> &lt; <span
style="color: blue">e</span> &lt; <span style="color: blue">f</span>
&lt; <span style="color: blue">g</span> &lt; <span
style="color: blue">p</span> &lt; <span style="color: blue">q</span>
&lt; <span style="color: blue">r</span> &lt; <span
style="color: blue">s</span>
</code></td>
</tr>
<tr>
<td><code>&lt;&lt;*</code></td>
<td><code>
&amp;<span style="color: blue"> a</span><br> &lt;&lt;*<span
style="color: blue"> æᶏɐ</span>
</code></td>
<td><code>
&amp;<span style="color: blue"> a</span><br> &lt;&lt;<span
style="color: blue"> æ </span>&lt;&lt; <span style="color: blue">ᶏ
</span>&lt;&lt; <span style="color: blue">ɐ</span>
</code></td>
</tr>
<tr>
<td><code>&lt;&lt;&lt;*</code></td>
<td><code>
&amp;<span style="color: blue"> p</span><br> &lt;&lt;&lt;* <span
style="color: blue">PｐＰ</span>
</code></td>
<td><code>
&amp;<span style="color: blue"> p</span><br> &lt;&lt;&lt; <span
style="color: blue">P</span> &lt;&lt;&lt; <span
style="color: blue">ｐ</span> &lt;&lt;&lt; <span
style="color: blue">Ｐ</span>
</code></td>
</tr>
<tr>
<td><code>&lt;&lt;&lt;&lt;*</code></td>
<td><code>
&amp;<span style="color: blue"> k</span><br>
&lt;&lt;&lt;&lt;* <span style="color: blue">qQ</span>
</code></td>
<td><code>
&amp;<span style="color: blue"> k</span><br> &lt;&lt;&lt;&lt;
<span style="color: blue">q</span> &lt;&lt;&lt;&lt; <span
style="color: blue">Q</span>
</code></td>
</tr>
<tr>
<td><code>=*</code></td>
<td><code>
&amp;<span style="color: blue"> v</span><br> =* <span
style="color: blue">VwW</span>
</code></td>
<td><code>
&amp;<span style="color: blue"> v</span><br> = <span
style="color: blue">V </span>= <span style="color: blue">w
</span>= <span style="color: blue">W</span>
</code></td>
</tr>
</table>
<h3>
3.7 <a name="Contractions" href="#Contractions">Contractions</a>
</h3>
<p>A multi-character relation string defines a contraction.</p>
<table>
<caption>
<a name="Specifying_Contractions" href="#Specifying_Contractions">Specifying
Contractions</a>
</caption>
<tr>
<th>Example</th>
<th>Description</th>
</tr>
<tr>
<td><code>
&amp; k<br> &lt; ch
</code></td>
<td>Make the sequence &#39;ch&#39; sort after &#39;k&#39;, as a
primary (base-character) difference</td>
</tr>
</table>
<h3>
3.8 <a name="Expansions" href="#Expansions">Expansions</a>
</h3>
<p>
A mapping to multiple collation elements defines an expansion. This
is normally the result of a reset position (and/or preceding
relation) that yields multiple collation elements, for example
<code>&amp;ae&lt;x</code>
or
<code>&amp;æ&lt;y</code>
.
</p>
<p>
A relation string can also be followed by
<code>/</code>
and an <i>extension string</i>. The extension string is mapped to
collation elements according to the current state, and the relation
string is mapped to the concatenation of the regular CEs and the
extension CEs. The extension CEs are not modified, not even their
case bits. The extension CEs are <i>not</i> retained for following
relations.
</p>
<p>
For example,
<code>&amp;a&lt;z/e</code>
maps ‘z’ to an expansion similar to
<code>&amp;ae&lt;x</code>
. However, the first CE of ‘z’ is primary-after that of ‘a’, and the
second CE is exactly that of ‘e’, which yields the order ae &lt; x
&lt; af &lt; ag &lt; ... &lt; az &lt; z &lt; b.
</p>
<p>
The choice of reset-to-expansion vs. use of an extension string can
be exploited to affect contextual mappings. For example,
<code>&amp;L·=x</code>
yields a second CE for ‘x’ equal to the context-sensitive
middle-dot-after-L (which is a secondary CE in the root collation).
On the other hand,
<code>&amp;L=x/·</code>
yields a second CE of the middle dot by itself (which is a primary
CE).
</p>
<p>
The two ways of specifying expansions also differ in how case bits
are computed. When some of the CEs are copied verbatim from an
extension string, then the relation string’s case bits are
distributed over a smaller number of normal CEs. For example,
<code>&amp;aE=Ch</code>
yields an uppercase CE and a lowercase CE, but
<code>&amp;a=Ch/E</code>
yields a mixed-case CE (for ‘C’ and ‘h’ together) followed by an
uppercase CE (copied from ‘E’).
</p>
<p>In summary, there are two ways of specifying expansions which
produce subtly different mappings. The use of extension strings is
unusual but sometimes necessary.</p>
<h3>
3.9 <a name="Context_Before" href="#Context_Before">Context
Before</a>
</h3>
<p>
A relation string can have a prefix (context before) which makes the
mapping from the relation string to its tailored position conditional
on the string occurring after that prefix. For details see the
specification of <i><a href="#Context_Sensitive_Mappings">Context-Sensitive
Mappings</a></i>.
</p>
<p>For example, suppose that &quot;-&quot; is sorted like the
previous vowel. Then one could have rules that take &quot;a-&quot;,
&quot;e-&quot;, and so on. However, that means that every time a very
common character (a, e, ...) is encountered, a system will slow down
as it looks for possible contractions. An alternative is to indicate
that when &quot;-&quot; is encountered, and it comes after an
&#39;a&#39;, it sorts like an &#39;a&#39;, and so on.</p>
<table>
<caption>
<a name="Specifying_Previous_Context"
href="#Specifying_Previous_Context">Specifying Previous Context</a>
</caption>
<tr>
<th>Rules</th>
</tr>
<tr>
<td><code>
&amp; a &lt;&lt;&lt; a | '-'<br> &amp; e &lt;&lt;&lt; e | '-'<br>
...
</code></td>
</tr>
</table>
<p>Both the prefix and extension strings can occur in a relation.
For example, the following are allowed:</p>
<ul>
<li><code>&lt; abc | def / ghi</code></li>
<li><code>&lt; def / ghi</code></li>
<li><code>&lt; abc | def</code></li>
</ul>
<h3>
3.10 <a name="Placing_Characters_Before_Others"
href="#Placing_Characters_Before_Others">Placing Characters
Before Others</a>
</h3>
<p>There are certain circumstances where characters need to be
placed before a given character, rather than after. This is the case
with Pinyin, for example, where certain accented letters are
positioned before the base letter. That is accomplished with the
following syntax.</p>
<pre>&amp;[before 2] a &lt;&lt; à</pre>
<p>The before-strength can be 1 (primary), 2 (secondary), or 3
(tertiary).</p>
<p>It is an error if the strength of the reset-before differs from
the strength of the immediately following relation. Thus the
following are errors.</p>
<ul>
<li><code>&amp;[before 2] a &lt; à # error</code></li>
<li><code>&amp;[before 2] a &lt;&lt;&lt; à # error</code></li>
</ul>
<h3>
3.11 <a name="Logical_Reset_Positions"
href="#Logical_Reset_Positions">Logical Reset Positions</a>
</h3>
<p>The CLDR table (based on UCA) has the following overall
structure for weights, going from low to high.</p>
<table>
<caption>
<a name="Specifying_Logical_Positions"
href="#Specifying_Logical_Positions">Specifying Logical
Positions</a>
</caption>
<tr>
<th>Name</th>
<th>Description</th>
<th>UCA Examples</th>
</tr>
<tr>
<td>first tertiary ignorable<br> ...<br> last
tertiary ignorable
</td>
<td>p, s, t = ignore</td>
<td>Control Codes<br> Format Characters<br> Hebrew
Points<br> Tibetan Signs<br> ...
</td>
</tr>
<tr>
<td>first secondary ignorable<br> ...<br> last
secondary ignorable
</td>
<td>p, s = ignore</td>
<td>None in UCA</td>
</tr>
<tr>
<td>first primary ignorable<br> ...<br> last primary
ignorable
</td>
<td>p = ignore</td>
<td>Most combining marks</td>
</tr>
<tr>
<td>first variable<br> ...<br> last variable
</td>
<td><i><b>if</b> alternate = non-ignorable<br> </i>p !=
ignore,<br> <i><b>if</b> alternate = shifted</i><br> p,
s, t = ignore</td>
<td>Whitespace,<br> Punctuation
</td>
</tr>
<tr>
<td>first regular<br> ...<br> last regular
</td>
<td>p != ignore</td>
<td>General Symbols<br> Currency Symbols<br> Numbers<br>
Latin<br> Greek<br> ...
</td>
</tr>
<tr>
<td>first implicit<br>...<br>last implicit
</td>
<td>p != ignore, assigned automatically</td>
<td>CJK, CJK compatibility (those that are not decomposed)<br>
CJK Extension A, B, C, ...<br> Unassigned
</td>
</tr>
<tr>
<td>first trailing<br> ...<br> last trailing
</td>
<td>p != ignore,<br> used for trailing syllable components
</td>
<td>Jamo Trailing<br> Jamo Leading<br>U+FFFD<br>U+FFFF
</td>
</tr>
</table>
<p>
Each of the above Names can be used with a reset to position
characters relative to that logical position. That allows characters
to be ordered before or after a <i>logical</i> position rather than a
specific character.
</p>
<blockquote>
<p class="note">
<b>Note: </b>The reason for this is so that tailorings can be more
stable. A future version of the UCA might add characters at any
point in the above list. Suppose that you set character X to be
after Y. It could be that you want X to come after Y, no matter what
future characters are added; or it could be that you just want Y to
come after a given logical position, for example, after the last
primary ignorable.
</p>
</blockquote>
<p>Each of these special reset positions always maps to a single
collation element.</p>
<p>Here is an example of the syntax:</p>
<pre>&amp; [first tertiary ignorable] &lt;&lt; à </pre>
<p>For example, to make a character be a secondary ignorable, one
can make it be immediately after (at a secondary level) a specific
character (like a combining diaeresis), or one can make it be
immediately after the last secondary ignorable.</p>
<p>
Each special reset position adjusts to the effects of preceding
rules, just like normal reset position strings. For example, if a
tailoring rule creates a new collation element after
<code>&amp;[last variable]</code>
(via explicit tailoring after that, or via tailoring after the
relevant character), then this new CE becomes the new <i>last
variable</i> CE, and is used in following resets to
<code>[last variable]</code>
.
</p>
<p>[first variable] and [first regular] and [first trailing]
should be the first real such CEs (e.g., CE(U+0060 &#x0060;)), as
adjusted according to the tailoring, not the boundary CEs (see the
FractionalUCA.txt “first primary” mappings starting with U+FDD1).</p>
<p>
<code>[last regular]</code>
is not actually the last normal CE with a primary weight before
implicit primaries. It is used to tailor large numbers of characters,
usually CJK, into the script=Hani range between the last regular
script and the first implicit CE. (The first group of implicit CEs is
for Han characters.) Therefore,
<code>[last regular]</code>
is set to the first Hani CE, the artificial script boundary CE at the
beginning of this range. For example:
<code>&amp;[last regular]&lt;*亜唖娃阿...</code>
</p>
<p>The [last trailing] is the CE of U+FFFF. Tailoring to that is
not allowed.</p>
<p>
The
<code>[last variable]</code>
indicates the &quot;highest&quot; character that is treated as
punctuation with alternate handling.
</p>
<p>
The value can be changed by using the maxVariable setting. This takes
effect, however, after the rules have been built, and does not affect
any characters that are reset relative to the
<code>[last variable]</code>
value when the rules are being built. The maxVariable setting might
also be changed via a runtime parameter. That also does not affect
the rules.<br> (In CLDR 24 and earlier, the variable top could
also be set by using a tailoring rule with
<code>[variable top]</code>
in the place of a relation string.)
</p>
<h3>
3.12 <a name="Special_Purpose_Commands"
href="#Special_Purpose_Commands">Special-Purpose Commands</a>
</h3>
<p>The import command imports rules from another collation. This
allows for better maintenance and smaller rule sizes. The source is a
BCP 47 language tag with an optional collation type but without other
extensions. The collation type is the BCP 47 form of the collation
type in the source; it defaults to "standard".</p>
<p>
<em>Examples: </em>
</p>
<ul>
<li><code>[import de-u-co-phonebk]</code> &nbsp; (not
"...-co-phonebook")</li>
<li><code>[import und-u-co-search]</code> &nbsp; (not
"root-...")</li>
<li><code>[import ja-u-co-private-kana]</code> &nbsp; (language
"ja" required even when this import itself is in another "ja"
tailoring.)</li>
</ul>
<table>
<caption>
<a name="Special_Purpose_Elements" href="#Special_Purpose_Elements">Special-Purpose
Elements</a>
</caption>
<tr>
<th>Rule Syntax</th>
</tr>
<tr>
<td>[suppressContractions [Љ-ґ]]</td>
</tr>
<tr>
<td>[optimize [Ά-ώ]]</td>
</tr>
</table>
<p>
The <i>suppress contractions</i> tailoring command turns off any
existing contractions that begin with those characters, as well as
any prefixes for those characters. It is typically used to turn off
the Cyrillic contractions in the UCA, since they are not used in many
languages and have a considerable performance penalty. The argument
is a <a href="tr35.html#Unicode_Sets">Unicode Set</a>.
</p>
<p>
The <i>suppress contractions</i> command has immediate effect on the
current set of mappings, including mappings added by preceding rules.
Following rules are processed after removing any context-sensitive
mappings originating from any of the characters in the set.
</p>
<p>
The <i>optimize</i> tailoring command is purely for performance. It
indicates that those characters are sufficiently common in the target
language for the tailoring that their performance should be enhanced.
</p>
<p>The reason that these are not settings is so that their
contents can be arbitrary characters.</p>
<hr width="50%">
<p>
<i>Example:</i>
</p>
<p>
The following is a simple example that combines portions of different
tailorings for illustration. For more complete examples, see the
actual locale data: <a
href="http://unicode.org/repos/cldr/tags/latest/common/collation/ja.xml">Japanese</a>,
<a
href="http://unicode.org/repos/cldr/tags/latest/common/collation/zh.xml">Chinese</a>,
<a
href="http://unicode.org/repos/cldr/tags/latest/common/collation/sv.xml">Swedish</a>,
and <a
href="http://unicode.org/repos/cldr/tags/latest/common/collation/de.xml">German</a>
(type=&quot;phonebook&quot;) are particularly illustrative.
</p>
<pre>&lt;collation&gt;
&lt;cr&gt;&lt;![CDATA[
[caseLevel on]
&amp;Z
&lt; æ &lt;&lt;&lt; Æ
&lt; å &lt;&lt;&lt; Å &lt;&lt;&lt; aa &lt;&lt;&lt; aA &lt;&lt;&lt; Aa &lt;&lt;&lt; AA
&lt; ä &lt;&lt;&lt; Ä
&lt; ö &lt;&lt;&lt; Ö &lt;&lt; ű &lt;&lt;&lt; Ű
&lt; ő &lt;&lt;&lt; Ő &lt;&lt; ø &lt;&lt;&lt; Ø
&amp;V &lt;&lt;&lt;* wW
&amp;Y &lt;&lt;&lt;* üÜ
&amp;[last non-ignorable]
<span style="color: green"># The following is equivalent to &lt;亜&lt;唖&lt;娃...</span>
&lt;* 亜唖娃阿哀愛挨姶逢葵茜穐悪握渥旭葦芦
&lt;* 鯵梓圧斡扱
]]&gt;&lt;/cr&gt;
&lt;/collation&gt;</pre>
<h3>
3.13 <a name="Script_Reordering" href="#Script_Reordering">Collation
Reordering</a>
</h3>
<p>Collation reordering allows scripts and certain other defined
blocks of characters to be moved relative to each other
parametrically, without changing the detailed rules for all the
characters involved. This reordering is done on top of any specific
ordering rules within the script or block currently in effect.
Reordering can specify groups to be placed at the start and/or the
end of the collation order. For example, to reorder Greek characters
before Latin characters, and digits afterwards (but before other
scripts), the following can be used:</p>
<table>
<tr>
<th>Rule Syntax</th>
<th>Locale Identifier</th>
</tr>
<tr>
<td><code>[reorder Grek Latn digit]</code></td>
<td><code>en-u-kr-grek-latn-digit</code></td>
</tr>
</table>
<p>
In each case, a sequence of <em><strong>reorder_codes</strong></em>
is used, separated by spaces in the settings attribute and in rule
syntax, and by hyphens in locale identifiers.
</p>
<p>
A <strong><em>reorder_code</em></strong> is any of the following
special codes:
</p>
<ol>
<li><strong>space, punct, symbol, currency, digit</strong> -
core groups of characters below 'a'</li>
<li><strong>any script code</strong> except <strong>Common</strong>
and <strong>Inherited</strong>.
<ul>
<li>Some pairs of scripts sort primary-equal and always
reorder together. For example, Katakana characters are are always
reordered with Hiragana.</li>
</ul></li>
<li><strong>others</strong> - where all codes not explicitly
mentioned should be ordered. The script code <strong>Zzzz</strong>
(Unknown Script) is a synonym for <strong>others</strong>.</li>
</ol>
<p>It is an error if a code occurs multiple times.</p>
<p>
It is an error if the sequence of reorder codes is empty in the XML
attribute or in the locale identifier. Some implementations may
interpret an empty sequence in the
<code>[reorder]</code>
rule syntax as a reset to the DUCET ordering, synonymous with
<code>[reorder others]</code>
; other implementations may forbid an empty sequence in the rule
syntax as well.
</p>
<p>
Interaction with <strong>alternate=shifted</strong>: Whether a
primary weight is “variable” is determined according to the “variable
top”, before applying script reordering. Once that is determined,
script reordering is applied to the primary weight regardless of
whether it is “regular” (used in the primary level) or “shifted”
(used in the quaternary level).
</p>
<h4>
3.13.1 <a name="Interpretation_reordering"
href="#Interpretation_reordering">Interpretation of a reordering
list</a>
</h4>
<p>The reordering list is interpreted as if it were processed in
the following way.</p>
<ol>
<li>If any core code is not present, then it is inserted at the
front of the list in the order given above.</li>
<li>If the <strong>others</strong> code is not present, then it
is inserted at the end of the list.
</li>
<li>The <strong>others</strong> code is replaced by the list of
all script codes not explicitly mentioned, in DUCET order.
</li>
<li>The reordering list is now complete, and used to reorder
characters in collation accordingly.</li>
</ol>
<p>
The locale data may have a particular ordering. For example, the
Czech locale data could put digits after all letters, with
<code>[reorder others digit]</code>
. Any reordering codes specified on top of that (such as with a bcp47
locale identifier) completely replace what was there. To specify a
version of collation that completely resets any existing reordering
to the DUCET ordering, the single code <strong>Zzzz</strong> or <strong>others</strong>
can be used, as below<strong></strong>.
</p>
<p>
<em>Examples: </em>
</p>
<table cellpadding="0" cellspacing="0">
<tbody>
<tr>
<th>Locale Identifier</th>
<th>Effect</th>
</tr>
<tr>
<td><code>en-u-kr-latn-digit</code></td>
<td>Reorder digits after Latin characters (but before other
scripts like Cyrillic).</td>
</tr>
<tr>
<td><code>en-u-kr-others-digit</code></td>
<td>Reorder digits after all other characters.</td>
</tr>
<tr>
<td><code>en-u-kr-arab-cyrl-others-symbol</code></td>
<td>Reorder Arabic characters first, then Cyrillic, and put
symbols at the end—after all other characters.</td>
</tr>
<tr>
<td><code>en-u-kr-others</code></td>
<td>Remove any locale-specific reordering, and use DUCET order
for reordering blocks.</td>
</tr>
</tbody>
</table>
<p>
The default reordering groups are defined by the FractionalUCA.txt
file, based on the primary weights of associated collation elements.
The file contains special mappings for the start of each group,
script, and reorder-reserved range, see <i>Section 2.6.2, <a
href="#File_Format_FractionalUCA_txt">FractionalUCA.txt</a></i>.
</p>
<p>There are some special cases:</p>
<ul>
<li>The <strong>Hani</strong> group includes implicit weights
for <em>Han characters</em> according to the UCA as well as any
characters tailored relative to a Han character, or after <code>&amp;[first
Hani]</code>.
</li>
<li>Implicit weights for <em>unassigned code points</em>
according to the UCA reorder as the last weights in the <strong>others</strong>
(<strong>Zzzz</strong>) group.<br> There is no script code to
explicitly reorder the unassigned-implicit weights into a particular
position. (Unassigned-implicit weights are used for non-Hani code
points without any mappings. For a given Unicode version they are
the code points with General_Category values Cn, Co, Cs.)
</li>
<li>The TRAILING group, the FIELD-SEPARATOR (associated with
U+FFFE), and collation elements with only zero primary weights are
not reordered.</li>
<li>The TERMINATOR, LEVEL-SEPARATOR, and SPECIAL groups are
never associated with characters.</li>
</ul>
<p>
For example,
<code>reorder="Hani Zzzz Grek"</code>
sorts Hani, Latin, Cyrillic, ... (all other scripts) ..., unassigned,
Greek, TRAILING.
</p>
<p>Notes for implementations that write sort keys:</p>
<ul>
<li>Primaries must always be offset by one or more whole primary
lead bytes. (Otherwise the number of bytes in a fractional weight
may change, compressible scripts may span multiple lead bytes, or
trailing primary bytes may collide with separators and
primary-compression terminators.)</li>
<li>When a script is reordered that does not start and end on
whole-primary-lead-byte boundaries, then the lead byte needs to be
“split”, and a reserved byte is used up. The data supports this via
reorder-reserved ranges of primary weights that are not used for
collation elements.</li>
<li>Primary weights from different original lead bytes can be
reordered to a shared lead byte, as long as they do not overlap.
Primary compression ends when the target lead byte differs or when
the original lead byte of the next primary is not compressible.</li>
<li>Non-compressible groups and scripts begin or end on
whole-primary-lead-byte boundaries (or both), so that reordering
cannot surround a non-compressible script by two compressible ones
within the same target lead byte. This is so that primary
compression can be terminated reliably (choosing the low or high
terminator byte) simply by comparing the previous and current
primary weights. Otherwise it would have to also check for another
condition (e.g., equal scripts).</li>
</ul>
<h4>
3.13.2 <a name="Reordering_Groups_allkeys"
href="#Reordering_Groups_allkeys">Reordering Groups for
allkeys.txt</a>
</h4>
<p>
For allkeys_CLDR.txt, the start of each reordering group can be
determined from FractionalUCA.txt, by finding the first real mapping
(after “xyz first primary”) of that group (e.g.,
<code>0060; [0D 07, 05, 05] # Zyyy Sk [0312.0020.0002] * GRAVE
ACCENT</code>
), and looking for that mapping's character sequence (
<code>0060</code>
) in allkeys_CLDR.txt. The comment in FractionalUCA.txt (
<code>[0312.0020.0002]</code>
) also shows the allkeys_CLDR.txt collation elements.
</p>
<p>The DUCET ordering of some characters is slightly different
from the CLDR root collation order. The reordering groups for the
DUCET are not specified. The following describes how reordering
groups for the DUCET can be derived.</p>
<p>
For allkeys_DUCET.txt, the start of each reordering group is normally
the primary weight corresponding to the same character sequence as
for allkeys_CLDR.txt. In a few cases this requires adjustment,
especially for the special reordering groups, due to CLDR’s ordering
the common characters more strictly by category than the DUCET (as
described in <i>Section 2, <a href="#Root_Collation">Root
Collation</a></i>). The necessary adjustment would set the start of each
allkeys_DUCET.txt reordering group to the primary weight of the first
mapping for the relevant General_Category for a special reordering
group (for characters that sort before ‘a’), or the primary weight of
the first mapping for the first script (e.g., sc=Grek) of an
“alphabetic” group (for characters that sort at or after ‘a’).
</p>
<p>Note that the following only applies to primary weights greater
than the one for U+FFFE and less than "trailing" weights.</p>
<p>The special reordering groups correspond to General_Category
values as follows:</p>
<ul>
<li>punct: P</li>
<li>symbol: Sk, Sm, So</li>
<li>space: Z, Cc</li>
<li>currency: Sc</li>
<li>digit: Nd</li>
</ul>
<p>In the DUCET, some characters that sort below ‘a’ and have
other General_Category values not mentioned above (e.g., gc=Lm) are
also grouped with symbols. Variants of numbers (gc=No or Nl) can be
found among punctuation, symbols, and digits.</p>
<p>Each collation element of an expansion may be in a different
reordering group, for example for parenthesized characters.</p>
<h3>
3.14 <a name="Case_Parameters" href="#Case_Parameters">Case
Parameters</a>
</h3>
<p>
The <strong>case level</strong> is an <em>optional</em> intermediate
level (&quot;2.5&quot;) between Level 2 and Level 3 (or after Level
1, if there is no Level 2 due to strength settings). The case level
is used to support two parametric features: ignoring non-case
variants (Level 3 differences) except for case, and giving case
differences a higher-level priority than other tertiary differences.
Distinctions between small and large Kana characters are also
included as case differences, to support Japanese collation.
</p>
<p>
The <strong>case first</strong> parameter controls whether to swap
the order of upper and lowercase. It can be used with or without the
case level.
</p>
<p>
Importantly, the case parameters have no effect in many instances.
For example, they have no effect on the comparison of two
non-ignorable characters with different primary weights, or with
different secondary weights if the strength = <strong>secondary
(or higher).</strong>
</p>
<p>
When either the <strong>case level</strong> or <strong>case
first</strong> parameters are set, the following describes the derivation of
the modified collation elements. It assumes the original levels for
the code point are [p.s.t] (primary, secondary, tertiary). This
derivation may change in future versions of LDML, to track the case
characteristics more closely.
</p>
<h4>
3.14.1 <a name="Case_Untailored" href="#Case_Untailored">Untailored
Characters</a>
</h4>
<p>For untailored characters and strings, that is, for mappings in
the root collation, the case value for each collation element is
computed from the tertiary weight listed in allkeys_CLDR.txt. This is
used to modify the collation element.</p>
<p>Look up a case value for the tertiary weight x of each
collation element:</p>
<ol>
<li>UPPER if x ∈ {08-0C, 0E, 11, 12, 1D}</li>
<li>UNCASED otherwise</li>
<li>FractionalUCA.txt encodes the case information in bits 6 and
7 of the first byte in each tertiary weight. The case bits are set
to 00 for UNCASED and LOWERCASE, and 10 for UPPER. There is no MIXED
case value (01) in the root collation.</li>
</ol>
<h4>
3.14.2 <a name="Case_Weights" href="#Case_Weights">Compute
Modified Collation Elements</a>
</h4>
<p>
From a computed case value, set a weight <strong>c</strong> according
to the following.
</p>
<ol>
<li>If <strong>CaseFirst=UpperFirst</strong>, set <strong>c</strong>
= UPPER ? <strong>1</strong> : MIXED ? 2 : <strong>3</strong></li>
<li>Otherwise set <strong>c</strong> = UPPER ? <strong>3</strong>
: MIXED ? 2 : <strong>1</strong></li>
</ol>
<p>
Compute a new collation element according to the following table. The
notation <em>xt</em> means that the values are numerically combined
into a single level, such that xt &lt; yu whenever x &lt; y. The
fourth level (if it exists) is unaffected. Note that a secondary CE
must have a secondary weight S which is greater than the secondary
weight s of any primary CE; and a tertiary CE must have a tertiary
weight T which is greater than the tertiary weight t of any primary
or secondary CE ([<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>] <a
href="http://www.unicode.org/reports/tr10/#WF2">WF2</a>).
</p>
<div align="center">
<table>
<tbody>
<tr>
<th>Case Level</th>
<th>Strength</th>
<th>Original CE</th>
<th>Modified CE</th>
<th>Comment</th>
</tr>
<tr>
<td rowspan="5"><strong>on</strong></td>
<td rowspan="2"><strong>primary</strong></td>
<td><code>0.S.t</code></td>
<td><code>0.0</code></td>
<td rowspan="2">ignore case level weights of
primary-ignorable CEs</td>
</tr>
<tr>
<td><code>p.s.t</code></td>
<td><code>p.c</code></td>
</tr>
<tr>
<td rowspan="3"><strong>secondary<br>
</strong>or higher</td>
<td><code>0.0.T</code></td>
<td><code>0.0.0.T</code></td>
<td rowspan="3">ignore case level weights of
secondary-ignorable CEs</td>
</tr>
<tr>
<td><code>0.S.t</code></td>
<td><code>0.S.c.t</code></td>
</tr>
<tr>
<td><code>p.s.t</code></td>
<td><code>p.s.c.t</code></td>
</tr>
<tr>
<td rowspan="4"><strong>off</strong></td>
<td rowspan="4">any</td>
<td><code>0.0.0</code></td>
<td><code>0.0.00</code></td>
<td rowspan="4">ignore case level weights of
tertiary-ignorable CEs</td>
</tr>
<tr>
<td><code>0.0.T</code></td>
<td><code> 0.0.3T </code></td>
</tr>
<tr>
<td><code>0.S.t</code></td>
<td><code>0.S.ct</code></td>
</tr>
<tr>
<td><code>p.s.t</code></td>
<td><code>p.s.ct</code></td>
</tr>
</tbody>
</table>
</div>
<p>For primary+case, which is used for “ignore accents but not
case” collation, primary ignorables are ignored so that a = ä. For
secondary+case, which would by analogy mean “ignore variants but not
case”, secondary ignorables are ignored for equivalent behavior.</p>
<p>
When using <strong>caseFirst</strong> but not <strong>caseLevel</strong>,
the combined case+tertiary weight of a tertiary CE must be greater
than the combined case+tertiary weight of any primary or secondary CE
so that [<a href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>]
<a href="http://www.unicode.org/reports/tr10/#WF2">well-formedness
condition 2</a> is fulfilled. Since the tertiary CE’s tertiary weight T
is already greater than any t of primary or secondary CEs, it is
sufficient to set its case weight to UPPER=3. It must not be affected
by <strong>caseFirst=upper</strong>. (The table uses the constant 3
in this case rather than the computed c.)
</p>
<p>
The case weight of a tertiary-ignorable CE must be 0 so that [<a
href="http://www.unicode.org/reports/tr41/#UTS10">UCA</a>] <a
href="http://www.unicode.org/reports/tr10/#WF1">well-formedness
condition 1</a> is fulfilled.
</p>
<h4>
3.14.3 <a name="Case_Tailored" href="#Case_Tailored">Tailored
Strings</a>
</h4>
<p>Characters and strings that are tailored have case values
computed from their root collation case bits.</p>
<ol>
<li>Look up the tailored string’s root CEs. (Ignore any prefix
or extension strings.) N=number of primary root CEs.</li>
<li>Determine the number and type (primary vs. weaker) of CEs a
tailored string maps to. M=number of primary tailored CEs.</li>
<li>If N&lt;=M (no more root than tailoring primary CEs): Copy
the root case bits for primary CEs 0..N-1.
<ul>
<li>If N&lt;M (fewer root primary CEs): Clear the case bits of
the remaining tailored primary CEs. (uncased/lowercase/small Kana)</li>
</ul>
</li>
<li>If N&gt;M (more root primary CEs): Copy the root case bits
for primary CEs 0..M-2. Set the case bits for tailored primary CE
M-1 according to the remaining root primary CEs M-1..N-1:
<ul>
<li>Set to uncased/lower if all remaining root primary CEs
have uncased/lower.</li>
<li>Set to uppercase if all remaining root primary CEs have
uppercase.</li>
<li>Otherwise, set to mixed.</li>
</ul>
</li>
<li>Clear the case bits for secondary CEs 0.s.t.</li>
<li>Tertiary CEs 0.0.t must get uppercase bits.</li>
<li>Tertiary-ignorable CEs 0.0.0 must get
ignorable-case=lowercase bits.</li>
</ol>
<p class="note">Note: Almost all Cased characters have primary
(non-ignorable) root collation CEs, except for U+0345 Combining
Ypogegrammeni which is Lowercase. All Uppercase characters have
primary root collation CEs.</p>
<h3>
3.15 <a name="Visibility" href="#Visibility">Visibility</a>
</h3>
<p>
Collations have external visibility by default, meaning that they can
be displayed in a list of collation options for users to choose from.
A collation whose type name starts with "private-" is internal and
should not be shown in such a list. Collations are typically internal
when they are partial sequences included in other collations. See <i>Section
3.1, <a href="#Collation_Types">Collation Types</a>
</i>.
</p>
<h3>
3.16 <a name="Collation_Indexes" href="#Collation_Indexes">Collation
Indexes</a>
</h3>
<h4>
3.16.1 <a name="Index_Characters" href="#Index_Characters">Index
Characters</a>
</h4>
<p>
The main data includes &lt;exemplarCharacters&gt; for collation
indexes. See <i>Part 2 General, Section 3, <a
href="tr35-general.html#Character_Elements">Character Elements</a></i>,
for general information about exemplar characters.
</p>
<p>The index characters are a set of characters for use as a UI
"index", that is, a list of clickable characters (or character
sequences) that allow the user to see a segment of a larger "target"
list. Each character corresponds to a bucket in the target list. One
may have different kinds of index lists; one that produces an index
list that is relatively static, and the other is a list that produces
roughly equally-sized buckets. While CLDR is mostly focused on the
first, there is provision for supporting the second as well.</p>
<p>The index characters need to be used in conjunction with a
collation for the locale, which will determine the order of the
characters. It will also determine which index characters show up.</p>
<p>The static list would be presented as something like the
following (either vertically or horizontally):</p>
<p align="center">… A B C D E F G H CH I J K L M N O P Q R S T U V
W X Y Z …</p>
<p>In the "A" bucket, you would find all items that are primary
greater than or equal to "A" in collation order, and primary less
than "B". The use of the list requires that the target list be sorted
according to the locale that is used to create that list. Although we
say "character" above, the index character could be a sequence, like
"CH" above. The index exemplar characters must always be used with a
collation appropriate for the locale. Any characters that do not have
primary differences from others in the set should be removed.</p>
<p>Details:</p>
<ol>
<li>The primary weight (according to the collation) is used to
determine which bucket a string is in. There are special buckets for
before the first character, between buckets of different scripts,
and after the last bucket (and of a different script).</li>
<li>Characters in the <em>index characters</em> do not need to
have distinct primary weights. That is, the <em>index
characters</em> are adapted to the underlying collation: normally Ё is
in the Е bucket for Russian, but if someone used a variant of
Russian collation that distinguished them on a primary level, then Ё
would show up as its own bucket.
</li>
<li>If an <em>index character</em> string ends with a single "*"
(U+002A), for example "Sch*" and "St*" in German, then there will be
a separate bucket for the string minus the "*", for example "Sch"
and "St", even if that string does not sort distinctly.
</li>
<li>An <em>index character</em> can have multiple primary
weights, for example "Æ" and "Sch". Names that have the same initial
primary weights sort into this <em>index character</em>’s bucket.
This can be achieved by using an upper-boundary string that is the
concatenation of the <em>index character</em> and U+FFFF, for
example "Æ\uFFFF" and "Sch\uFFFF". Names that sort greater than this
upper boundary but less than the next index character are redirected
to the last preceding single-primary index character (A and S for
the examples here).
</li>
</ol>
<p>
For example, for index characters
<code>[A Æ B R S {Sch*} {St*} T]</code>
the following sample names are sorted into an index as shown.
</p>
<ul>
<li>A &mdash; Adelbert, Afrika</li>
<li>Æ &mdash; Æsculap, Aesthet</li>
<li>B &mdash; Berlin</li>
<li>R &mdash; Rilke</li>
<li>S &mdash; Sacher, Seiler, Sultan</li>
<li>Sch &mdash; Schiller</li>
<li>St &mdash; Steiff</li>
<li>T &mdash; Thomas</li>
</ul>
<p>
The … items are special: each is a bucket for everything else, either
less or greater. They are inserted at the start and end of the index
list, <em>and</em> on script boundaries. Each script has its own
range, except where scripts sort primary-equal (e.g., Hira &amp;
Kana). All characters that sort in one of the low reordering groups
(whitespace, punctuation, symbols, currency symbols, digits) are
treated as a single script for this purpose.
</p>
<p>If you tailor a Greek character into the Cyrillic script, that
Greek character will be bucketed (and sorted) among the Cyrillic
ones.</p>
<p>
Even in an implementation that reorders groups of scripts rather than
single scripts, for example Hebrew together with Phoenician and
Samaritan, the index boundaries are really script boundaries, <em>not</em>
multi-script-group boundaries. So if you had a collation that
reordered Hebrew after Ethiopic, you would still get index boundaries
between the following (and in that order):
</p>
<ol>
<li>Ethiopic</li>
<li>Hebrew</li>
<li>Phoenician<em> // included in the Hebrew reordering
group</em></li>
<li>Samaritan<em> // included in the Hebrew reordering
group</em></li>
<li>Devanagari</li>
</ol>
<p>(Beginning with CLDR 27, single scripts can be reordered.)</p>
<p>In the UI, an index character could also be omitted or grayed
out if its bucket is empty. For example, if there is nothing in the
bucket for Q, then Q could be omitted. That would be up to the
implementation. Additional buckets could be added if other characters
are present. For example, we might see something like the following:</p>
<table border="1" cellspacing="0">
<tbody>
<tr align="center">
<td><div align="center">
<strong>Sample Greek Index<br>
</strong>
</div></td>
<td><strong>Contents<br>
</strong></td>
</tr>
<tr align="center">
<td><div align="center"> Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ Ο Π
Ρ Σ Τ Υ Φ Χ Ψ Ω</div></td>
<td>With only content beginning with Greek letters <br>
</td>
</tr>
<tr align="center">
<td><div align="center"> … Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ Ο
Π Ρ Σ Τ Υ Φ Χ Ψ Ω …</div></td>
<td>With some content before or after</td>
</tr>
<tr align="center">
<td><div align="center"> … 9 Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ
Ο Π Ρ Σ Τ Υ Φ Χ Ψ Ω …</div></td>
<td>With numbers, and nothing between 9 and Alpha</td>
</tr>
<tr align="center">
<td><div align="center">
  … 9 <em>A-Z</em> Α Β Γ Δ Ε Ζ Η Θ Ι Κ Λ Μ Ν Ξ Ο Π Ρ Σ Τ Υ Φ Χ Ψ
Ω …
</div></td>
<td>With numbers, some Latin</td>
</tr>
</tbody>
</table>
<p>Here is a sample of the XML structure:</p>
<pre>&lt;exemplarCharacters type=&quot;index&quot;&gt;[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z]&lt;/exemplarCharacters&gt;</pre>
<p>
The display of the index characters can be modified with the Index
labels elements, discussed in the <i>Part 2 General, Section 3.3,
<a href="tr35-general.html#IndexLabels">Index Labels</a>
</i>.
</p>
<h4>
3.16.2 <a name="CJK_Index_Markers" href="#CJK_Index_Markers">CJK
Index Markers</a>
</h4>
<p>Special index markers have been added to the CJK collations for
stroke, pinyin, zhuyin, and unihan. These markers allow for effective
and robust use of indexes for these collations.</p>
<p>The per-language index exemplar characters are not useful for
collation indexes for CJK because for each such language there are
multiple sort orders in use (for example, Chinese pinyin vs. stroke
vs. unihan vs. zhuyin), and these sort orders use very different
index characters. In addition, sometimes the boundary strings are
different from the bucket label strings. For collations that contain
index markers, the boundary strings and bucket labels should be
derived from those index markers, ignoring the index exemplar
characters.</p>
<p>For example, near the start of the pinyin tailoring there is
the following:</p>
<p>
&lt;p&gt; A&lt;/p&gt;&lt;!-- INDEX A --&gt;<br>
&lt;pc&gt;阿呵𥥩锕𠼞𨉚&lt;/pc&gt;&lt;!-- ā --&gt;
</p>
<p>…</p>
<p>
&lt;pc&gt;翶&lt;/pc&gt;&lt;!-- ao --&gt;<br> &lt;p&gt;
B&lt;/p&gt;&lt;!-- INDEX B --&gt;
</p>
<p>These indicate the boundaries of &quot;buckets&quot; that can
be used for indexing. They are always two characters starting with
the noncharacter U+FDD0, and thus will not occur in normal text. For
pinyin the second character is A-Z; for unihan it is one of the
radicals; and for stroke it is a character after U+2800 indicating
the number of strokes, such as ⠁. For zhuyin the second character is
one of the standard Bopomofo characters in the range U+3105 through
U+3129.</p>
<p>The corresponding bucket label strings are the boundary strings
with the leading U+FDD0 removed. For example, the Pinyin boundary
string "\uFDD0A" yields the label string "A".</p>
<p>However, for stroke order, the label string is the stroke count
(second character minus U+2800) as a decimal-digit number followed by
&#x5283; (U+5283). For example, the stroke order boundary string
"\uFDD0\u2805" yields the label string "5&#x5283;".</p>
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