Matching of Language Tags
RFC 4647
| Document | Type |
RFC - Best Current Practice
(September 2006; No errata)
Obsoletes RFC 3066
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4647 (Best Current Practice) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Ted Hardie | ||
| Send notices to | (None) | ||
Network Working Group A. Phillips, Ed.
Request for Comments: 4647 Yahoo! Inc.
BCP: 47 M. Davis, Ed.
Obsoletes: 3066 Google
Category: Best Current Practice September 2006
Matching of Language Tags
Status of This Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document describes a syntax, called a "language-range", for
specifying items in a user's list of language preferences. It also
describes different mechanisms for comparing and matching these to
language tags. Two kinds of matching mechanisms, filtering and
lookup, are defined. Filtering produces a (potentially empty) set of
language tags, whereas lookup produces a single language tag.
Possible applications include language negotiation or content
selection. This document, in combination with RFC 4646, replaces RFC
3066, which replaced RFC 1766.
Phillips & Davis Best Current Practice [Page 1]
RFC 4647 Matching of Language Tags September 2006
Table of Contents
1. Introduction ....................................................3
2. The Language Range ..............................................3
2.1. Basic Language Range .......................................4
2.2. Extended Language Range ....................................4
2.3. The Language Priority List .................................5
3. Types of Matching ...............................................6
3.1. Choosing a Matching Scheme .................................6
3.2. Implementation Considerations ..............................7
3.3. Filtering ..................................................8
3.3.1. Basic Filtering .....................................9
3.3.2. Extended Filtering .................................10
3.4. Lookup ....................................................12
3.4.1. Default Values .....................................14
4. Other Considerations ...........................................15
4.1. Choosing Language Ranges ..................................15
4.2. Meaning of Language Tags and Ranges .......................16
4.3. Considerations for Private-Use Subtags ....................17
4.4. Length Considerations for Language Ranges .................17
5. Security Considerations ........................................17
6. Character Set Considerations ...................................17
7. References .....................................................18
7.1. Normative References ......................................18
7.2. Informative References ....................................18
Appendix A. Acknowledgements ......................................19
Phillips & Davis Best Current Practice [Page 2]
RFC 4647 Matching of Language Tags September 2006
1. Introduction
Human beings on our planet have, past and present, used a number of
languages. There are many reasons why one would want to identify the
language used when presenting or requesting information.
Applications, protocols, or specifications that use language
identifiers, such as the language tags defined in [RFC4646],
sometimes need to match language tags to a user's language
preferences.
This document defines a syntax (called a language range (Section 2))
for specifying items in the user's list of language preferences
(called a language priority list (Section 2.3)), as well as several
schemes for selecting or filtering sets of language tags by comparing
the language tags to the user's preferences. Applications,
protocols, or specifications will have varying needs and requirements
that affect the choice of a suitable matching scheme.
This document describes how to indicate a user's preferences using
language ranges, three schemes for matching these ranges to a set of
language tags, and the various practical considerations that apply to
implementing and using these schemes.
This document, in combination with [RFC4646], replaces [RFC3066],
which replaced [RFC1766].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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