Larry Masinter <email@example.com> Fri, 02 May 1997 11:24 UTC
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Date: Fri, 02 May 1997 03:57:08 -0700
From: Larry Masinter <firstname.lastname@example.org>
Organization: Xerox PARC
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INTERNET-DRAFT Larry Masinter, Xerox Corporation draft-masinter-url-i18n-00 May 2, 1997 Expires: October 27, 1997 Using UTF-8 for non-ASCII Characters in URLs Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract Traditionally, URLs have been written in ASCII and used both as a method of transcription and identification, but also in advertising, magazines and newspapers. This document specifies a uniform way of representing non-ASCII scripts in URLs so that they can be used for the world's languages. This document is still very rough. 1. Introduction URLs were defined as ASCII-only.[RFC-URL-SYNTAX] This leaves out most of the world of people, who do not write merely with the letters A-Z. 2. Syntax This memo defines two kinds of URLs: Internationalized but hex-encoded URLs (compatible with [RFC-URL-SYNTAX], and 8-bit URLs. For traditional URLs, characters should be translated into UTF8 and then any octet not allowed in RFC-URL-SYNTAX should be hex-encoded. For 8-bit-URLs, it is necessary to hex-encode reserved characters, delims, unwise special characters, white space, and characters that might otherwise be confusing when printed and then typed. (See RFC-DURST for details.) 3. Software Requirements Supporting UTF-8 URLs requires cooperation from the providers of three different components of URL software. 3.1 Requirements for URL entry One component of software that deals with URLs allows users to type in the URLs. That is, a human transcribes a visual representation of a URL (as a sequence of glyphs, in some order, in some visual display) using some entry method that will result in a URL. If the visual representation contains only those characters that were defined as part of the [RFC-URL-SYNTAX] standard syntax of URLs, the transcription would be simple. However, for all other sequences of characters, entry should result in characters, in logical order, from the ISO 10646 character repertoire, encoded using the UTF-8 method [RFC 2044], and then subsequently encoded using the URL escape mechanism [RFC-URL-SYNTAX]. Some care must be taken in this conversion, for example, that all accented characters should be translated into their combined form, that no extraneous BIDI marks be left in the resulting stream, that any characters that _look_ like ASCII characters be transcribed into their ascii equivalents and not, for example, as double-wide characters. See [RFC-DUERST] for more complete rules. 3.2 Requirements for URL generation and interpretation Systems that are offering resources through the internet where those resources have logical names sometimes offer the ability to generate URLs for the resources they offer. For example, some HTTP servers offer the ability to generate a 'directory listing' for file directories under their purvue, and then to respond to the generated URLs with the files. If the names of the files consist solely of US-ASCII characters, the transcription is simple, but other file systems offer a wider variety of characters. The generation of directories should result in hex-encoded UTF-8 for non-US-ASCII characters in the listing, for maximum interoperability. When a URL is recieved, the software should accept both the raw UTF-8 or the hex-encoded version. This recommendation applies to HTTP servers, and also to FTP servers, gopher servers, etc. 3.3 Requirements for display of URLs Software that displays URLs to users (or other kinds of transcription, e.g., deciding what to print in your magazine) should of course be robust: don't tell users about a URL they can't type! 1) any 'forbidden' octets should be displayed as if they were UTF-8 encoded characters. That is, those octets are currently disallowed in URLs, but if you see them, display them in a standard way. 2) Any sequences of %HH-encoded octets should be displayed EITHER as <%><H><H>, e.g., just show the encoding in ASCII, OR by assuming that they're hex-encoded UTF-8. The latter assumption is likely to be wrong for now, but might change later. Summary These three recommendations, when taken together, will allow for localization of URLs; users may use their native scripts for writing URLs that are "uniform" for their context. Acknowledgements Martin Duerst References [RFC 2044] [RFC-URL-SYNTAX] draft-fielding-url-syntax [RFC-DUERST] draft-duerst-url-???
- draft-masinter-url-i18n-00.txt Larry Masinter