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Based on [RFC 3066bis] and [RFC 3066bis Matching], this document describes mechanisms for identifying or selecting the language of content or locale preferences used to process information using Web technologies. It describes how document formats, specifications, and implementations should handle language tags, as well as data structures that extend these tags to describe international preferences.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.
This is an updated Public Working Draft of "Language and Locale Identifiers for the World Wide Web (LTLI)".
This document describes mechanisms for identifying or selecting the language of content or locale preferences used to process information using Web technologies. It describes how document formats, specifications, and implementations should handle language tags, as well as data structures that extend these tags to describe international preferences.
This document was developed by the Internationalization Core Working Group, part of the W3C Internationalization Activity. The Working Group expects to advance this Working Draft to Recommendation Status. A complete list of changes to this document is available.
Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.
This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This section is informative.
This document describes mechanisms for identifying or selecting the language of content or locale preferences used to process information using Web technologies. It describes how document formats, specifications, and implementations should handle the language tags described by [BCP 47], as well as data structures that extend these tags to describe international preferences (see sec. 3.1 in [WS-I18N Scenarios]).
Identification of language and locale has a broad range of applications within the World Wide Web. Existing standards which make use of language identification includes the
xml:lang attribute in [XML 1.0], the
hreflang atttributes in [HTML 4.01], or the
language property in [XSL 1.0]. Locale identification is used for example within the CLDR project, cf. [LDML].
The current best practice when developing specifications for language identification is to refer to [RFC 3066], using a formulation like "RFC 3066 or its successor". Recently a successor for [RFC 3066] has been developed, called [RFC 3066bis]. This specification takes [RFC 3066bis] as the basis for language identification, and [RFC 3066bis Matching] as the basis for matching of language identifiers ("tags").
The current practice in many standards is to identify language in terms of [RFC 3066], using formulations like "RFC 3066 or its successor". Recently a successor for [RFC 3066] has been developed, called [RFC 3066bis]. This specification takes [RFC 3066bis] as the basis for language identification, and [RFC 3066bis Matching] as the basis for matching of language tags.
[RFC 3066bis] refers to language identification only. Locales can be identified in several ways. One method is by inference from language tags. For example, an implementation could map a language tag from an existing protocol, such as HTTP's Accept-Language header, to its locale model. Locales may also be identified directly by using the language tag syntax in data items (elements, attributes, headers, etc.) that explicitly serve the purpose of locale identification.
Currently, this specification refers to [RFC 3066bis] and [RFC 3066bis Matching] directly. Since [RFC 3066bis] and [RFC 3066bis Matching] are expected to become the new BCP 47 before this working draft becomes a recommendation, a later draft of this specification will refer to BCP 47 directly.
This specification will not deal with formats for locale data or actual locale data. One possible source of locale data and data formats is [LDML].
In order to enable multi-locale operation of Web services and to create the ability for locale negotiation, this specification describes a standardized method for identifying locales and locale and/or language tags on the Web, including non-normative guidelines for implementation. This is called out in Requirement R005 of [WS-I18N Req]. The mechanism for language and locale identification which is defined in this specification will be used in a future version of the description of Web services Internationalization in [WS-I18N].
Further application scenarios of this specification encompass for example the standards mentioned in Section 1.1: Scope of this Specification. The scenarios can be divided in four areas:
Definition of values for language tags
Definition of values for locale identifiers
Definition of matching schemes for language tags
Definition of matching schemes for locale identifiers
As for matching of language tags, many specifications already define operations using matching. An example is the language pseudo-class
:lang defined in sec. 5.11.4 of [CSS 2.1]. It matches elements based on their language. This specification formulates requirements on such operations, based on [RFC 3066bis Matching].
This document defines locale identifiers for use in Web technologies. Historically, natural language identifiers [RFC 3066bis] have been used as locale identifiers by some programming languages or operating environments, which is natural since locale identifiers usually share certain core features related to natural language and country/region. This specification defines locale identifiers that specific locale implementations can map to their proprietary features in order to create functional, interoperable applications.
The minimal requirement is the ability to specify the natural language; thus there is industry convergence on the use of [RFC 3066bis] as the core of a locale identifier. For example, [CLDR] uses [RFC 3066bis] as the core of a locale identifier, and provides syntax for extensions for non-linguistic information, such as preferred currency or timezone.
A major difference between language tags and locale identifiers is the meaning of the region code. In both language tags and locales, the region code indicates variation in language (as with regional dialects) or presentation and format (such as number or date formats). In a locale, the region code is also sometimes used to indicate the physical location, market, legal, or other governing policies for the user.
The language tag may be available in several places. In HTTP, there is an Accept-Language header field which can be used. MIME has a Content-Language header which contains a language tag. In XML, there is an attribute which can be defined for elements called
xml:lang marks all the contents and attribute values of the corresponding element as belonging to the language identified. What that means for processing those contents varies from application to application.
For more detailed information on the behavior of
xml:lang, see [XML 1.0].
This section is normative.
This document uses the terms language tag and subtag which are defined in [RFC 3066bis].
In addition, this document uses the following terms, which are defined in [RFC 3066bis Matching]:
basic language range (see sec. 2.1 of [RFC 3066bis Matching])
extended language range (see sec. 2.2 of [RFC 3066bis Matching])
language priority list (see sec. 2.3 of [RFC 3066bis Matching])
de-de is a basic language range. It matches e.g. the language tag
de-DE-1996, but not the language tag
de-*-DE is an extended language range. It matches all of the
"en; fr; zh-Hant" is a language priority list. It would be read as "English before French before Chinese as
written in the Traditional script". Note that the syntax shown is only an example, since it depends on the protocol, application, or
implementation that uses the list.
This section is normative
This section explains the conditions that specifications have to fulfill to be able to claim conformance to this specification.
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119].
This section is normative
The following requirements are formulated for specifications who deal with language tags and locale values or matching schemes.
Specifications that make use of language tags or locale values MUST meet the conformance criteria defined for "well-formed" processors, as defined in sec. 2.2.9 of [RFC 3066bis].
Specifications that make use of language tags or locale values MAY validate these values. If they do so, they MUST meet the conformance criteria defined for "validating" processors, as defined in sec. 2.2.9 of [RFC 3066bis].
Specifications that define operations on language tags or locale values using matching Must use either a basic language range or an extended language range.
Specifications that define operations on language tags or locale values using matching MUST specify whether the resulting language priority list contains a single result (lookup as defined in [RFC 3066bis Matching]), or a possible empty set of results (filtering as defined in [RFC 3066bis Matching]).
The following log records changes that have been made to this document since the publication in April 2006.
The informative introductory section has been rewritten thoroughly, including the description of the scope of the document, of application scenarios and of the separation locale versus natural language.
Terms which rely on [RFC 3066bis] and [RFC 3066bis Matching] are not defined anymore, but only reference these documents, see Section 2.1: Language Tags and Matching of Language Tags. In addition, examples for these terms have been created.
A revision log has been created.