1 <?xml version="1.0" encoding="US-ASCII"?> 2 <!DOCTYPE rfc SYSTEM "rfc2629.dtd" [ 3 <!ENTITY RFC4646 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4646.xml"> 4 <!ENTITY rfc5646 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5646.xml"> 5 ]> 6 <?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> 7 8 <?rfc strict="yes" ?> 9 <?rfc toc="yes"?> 10 <?rfc tocdepth="4"?> 11 <?rfc symrefs="yes"?> 12 <?rfc sortrefs="yes" ?> 13 <?rfc compact="yes" ?> 14 <?rfc subcompact="no" ?> 15 16 17 <rfc category="bcp" docName="draft-davis-u-langtag-ext-00" ipr="trust200902" submissionType="independent"> 18 19 20 21 22 <front> 23 24 25 <title abbrev="BCP 47 Unicode Locale Extension">BCP 47 Extension U</title> 26 27 <author fullname="Mark Davis" initials="M.E." surname="Davis"> 28 <organization>Google</organization> 29 30 <address> 31 32 33 34 35 <email>mark (a] macchiato.com</email> 36 37 38 </address> 39 </author> 40 41 <author fullname="Addison Phillips" initials="A" surname="Phillips"> 42 <organization>Lab126</organization> 43 44 <address><email>addison (a] inter-locale.com</email></address> 45 </author> 46 47 <author initials="Y" surname="Umaoka" fullname="Yoshito Umaoka"><organization abbrev="IBM">IBM</organization><address><email>yoshito_umaoka (a] us.ibm.com</email></address></author><date month="January" year="2010" day="13"/> 48 49 50 51 <!-- Meta-data Declarations --> 52 53 <area>General</area> 54 55 <workgroup>Internet Engineering Task Force</workgroup> 56 57 58 59 <keyword>locale</keyword><keyword>bcp 47</keyword> 60 61 <!-- Keywords will be incorporated into HTML output 62 files in a meta tag but they have no effect on text or nroff 63 output. If you submit your draft to the RFC Editor, the 64 keywords will be used for the search engine. --> 65 66 <abstract> 67 <t>This document specifies an Extension to BCP 47 68 which provides subtags that specify language and/or locale-based behavior or refinements to language tags, according 69 to work done by the Unicode Consortium.</t> 70 </abstract> 71 </front> 72 73 <middle> 74 <section title="Introduction"> 75 <t> <xref target="BCP47"></xref> permits the definition and registration of language tag extensions "that 76 contain a language component and are compatible with applications that 77 understand language tags". This document defines an extension for identifying Unicode locale-based variations using language tags. The "singleton" identifier for this extension is 'u'.</t> 78 79 <section title="Requirements Language"> 80 <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 82 document are to be interpreted as described in RFC 2119.</t> 83 </section> 84 </section> 85 86 87 88 <?rfc needLines="8" ?> 89 90 <section title="BCP47 Required Information"> 91 <t>Language tags, as defined by <xref target="BCP47"></xref>, are useful for identifying the language of content. They are also used as locale identifiers (or can be mapped to locales) in many operating environments and APIs. However, most such locale identifiers also provide additional "tailorings" or options for specific values within a language, culture, region, or other variation. This extension provides a mechanism for using these additional tailorings within language tags for general interchange.</t><t> The maintaining authority for this extension's registry is the Unicode 92 Consortium. Unicode defines common locale data and identifiers for this data:</t> 93 94 <texttable> 95 <ttcol>Item</ttcol> 96 97 <ttcol>Value</ttcol> 98 99 <c>Name</c> 100 101 <c>Unicode Consortium</c> 102 103 <c>Contact Email</c> 104 105 <c>cldr (a] unicode.org</c> 106 107 <c>Discussion List Email</c> 108 109 <c>cldr-users (a] unicode.org</c> 110 111 <c>URL Location</c> 112 113 <c>cldr.unicode.org</c> 114 115 <c>Specification</c> 116 117 <c>Unicode Technical Standard #35 Unicode Locale Data Markup Language 118 (LDML), http://unicode.org/reports/tr35/</c> 119 120 <c>Section</c> 121 122 <c>Section 3.2 BCP 47 Tag Conversion</c> 123 </texttable> 124 125 <t>The specification of extension subtags is provided by Section 3 of <xref target="LDML">Unicode 126 Technical Standard #35 Unicode Locale Data Markup Language</xref>. As required by BCP 47, subtags follow the language tag ABNF and 127 other rules for the formation of language tags and subtags, are restricted to the ASCII letters and digits, are not case sensitive, and do not exceed eight characters in length.</t> 128 <t><xref target="LDML"></xref> specifies a canonical 129 representation. LDML is available over the Internet and at no cost, and 130 is available via a royalty-free license at 131 http://unicode.org/copyright.html. LDML is versioned, and each 132 version of LDML is numbered, dated, and stable. Extension subtags, once 133 defined by LDML, are never retracted or change in meaning in a 134 substantial way. </t> 135 136 <section title="Summary"> 137 <t>The subtags available for use in the 'u' extension consist of a set of attributes, keys, and types. Attributes, keys, types, and their respective meanings are defined in Section 3 (Unicode Language and Locale Identifiers) of <xref target="LDML"></xref>. The following is a summary of that definition (for details see Section 3):<list style="symbols"><t>An 'attribute' is a subtag with a length of three or more characters following the singleton and preceding any 'keyword' sequences. No attributes were defined at the time of this document's publication.</t><t>A 'keyword' is a sequence of subtags consisting of a 'key' subtag, followed by zero or more 'type' subtags. Each 'key' MUST be unique within the extension. The order of the 'type' subtags within a 'keyword' is sometimes significant to their interpretation. Note that 'keys' can appear without a subsequent 'type' subtag.<list style="letters"><t>A 'key' is a subtag with a length of exactly two characters. Each 'key' is followed by zero or more 'type' subtags. </t><t>A 'type' is a subtag with a length of three or more characters following a key. 'Type' subtags are specific to a particular 'key' and the order of the 'type' subtags MAY be significant to the interpretation of the 'keyword'.</t></list></t></list></t><t>For example, the language tag "de-DE-u-attr-co-phonebk" consists of:<list style="symbols"><t>The base language tag "de-DE" (German as used in Germany), exactly as defined by <xref target="BCP47"></xref> using subtags from the IANA Language Subtag Registry.</t><t>The singleton 'u', identifying this extension.</t><t>The attribute 'attr', which is an example for illustration (no attributes were defined at the time this document was published).</t><t>The keyword 'co-phonebk', consisting to the key 'co' (Collation) and the type 'phonebk' (Phonebook collation order).</t></list></t><t>With successive versions of <xref target="LDML"></xref>, additional attributes, keys, and types MAY be defined. Once defined, attributes, keys, and types will never be removed. Machine-readable files listing the valid attributes, keys, and types are available in the CLDR repository for each version. For example, for version 1.7.2, the files are located at <eref target="http://unicode.org/repos/cldr/tags/release-1-7-2/common/bcp47/">http://unicode.org/repos/cldr/tags/release-1-7-2/common/bcp47/</eref>. These also can contain aliases which were used in previous versions of <xref target="LDML"></xref>.</t><section title="Canonicalization" anchor="canonicalization"><t>As required by <xref target="BCP47"></xref>, case is not significant. The canonical form for all subtags in the extension is lowercase. The canonical order of attributes is in <xref target="US-ASCII"></xref> order (that is, numbers before letters, with letters sorted as lowercase US-ASCII code points). The canonical order of keywords is in <xref target="US-ASCII"></xref> order by key. The order of subtags within a keyword is significant; the meaning of this extension is altered if those subtags are rearranged. Thus, the canonical form of the extension never reorders the subtags within a keyword.</t> 138 139 140 </section></section> 141 142 <section title="Registration Form" anchor="regform"><t>Per <xref target="RFC5646"></xref>, Section 3.7:</t> 143 <figure><artwork>%% 144 Identifier: u 145 Description: Unicode Locale 146 Comments: Subtags for the identification of language and cultural 147 variations. Used to set behavior in locale APIs. 148 Added: 2009-mm-dd 149 RFC: [TBD] 150 Authority: Unicode Consortium 151 Contact_Email: cldr (a] unicode.org 152 Mailing_List: cldr-users (a] unicode.org 153 URL: http://cldr.unicode.org 154 %%</artwork></figure> 155 156 157 </section> 158 </section> 159 160 <section anchor="Acknowledgements" title="Acknowledgements"> 161 <t>Thanks to John Emmons and the rest of the Unicode 162 CLDR Technical Committee for their work in developing the BCP 47 subtags 163 for LDML.</t> 164 </section> 165 166 <section anchor="IANA" title="IANA Considerations"> 167 <t>This document will require IANA to insert the record in <xref target="regform"></xref> into the Language Extensions Registry, according to 168 Section 3.7. Extensions and the Extensions Registry of "Tags for 169 Identifying Languages" in <xref target="BCP47"></xref>. There might be occasional maintenance of this record. This document does not require IANA to create or maintain a new registry or otherwise impact IANA.</t> 170 </section> 171 172 <section anchor="Security" title="Security Considerations"> 173 <t>The security considerations for this extension are the same as those 174 for <xref target="RFC5646"></xref> (or its successors). See Section 6. Security Considerations 175 of <xref target="RFC5646"></xref>.</t> 176 </section> 177 </middle> 178 179 180 181 <back> 182 <references title="Normative References">&rfc5646; 183 <reference anchor="LDML" target="http://www.unicode.org/reports/tr35/"> 184 <front> 185 <title abbrev="LDML"> 186 Unicode Technical Standard #35: Locale Data Markup Language (LDML) 187 </title> 188 <author initials="M" surname="Davis" fullname="Mark Davis"> 189 <organization>Unicode Consortium</organization> 190 </author> 191 <date day="21" month="December" year="2007"/> 192 </front> 193 </reference> <reference anchor="BCP47"><front><title abbrev="BCP47">Tags for the Identification of Language (BCP47)</title><author initials="M.E." surname="Davis" fullname="Mark Davis" role="editor"><organization><?xm-replace_text {organization}?></organization></author><date month="September" year="2009"/></front></reference><reference anchor="US-ASCII"> 194 <front> 195 <title>ISO/IEC 646:1991, Information technology -- ISO 7-bit coded character set for information interchange. </title> 196 <author> 197 <organization>International Organization for Standardization</organization> 198 </author> 199 <date year="1991"/> 200 <abstract> 201 <t>This standard defines an International Reference Version (IRV) which corresponds exactly to what is widely known as ASCII or US-ASCII. ISO/IEC 646 was based on the earlier standard ECMA-6. ECMA has maintained its standard up to date with respect to ISO/IEC 646 and makes an electronic copy available at http://www.ecma-international.org/publications/standards/Ecma-006.htm. ISO/IEC 646 JTC 1/SC 2</t> 202 </abstract> 203 </front> 204 </reference></references><references title="Informative References"><reference anchor="ldml-registry"><front><title>Registry for Common Locale Data Repository tag elements</title><author fullname="Unicode Consortium"><organization><?xm-replace_text {organization}?></organization></author><date year="2009" month="September"/></front></reference></references> 205 206 207 </back> 208 </rfc> 209
