Network Working Group F. Yergeau Internet Draft G. Nicol G. Adams Expires 18 August 1996 M. Duerst 13 February 1996 Internationalization of the Hypertext Markup Language Status of this Memo This document is an Internet-Draft. Internet-Drafts are working doc- uments of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute work- ing documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months. Internet-Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet- Drafts as reference material or to cite them other than as a "working draft" or "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 ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Distribution of this document is unlimited. Please send comments to the HTML working group (HTML-WG) of the Internet Engineering Task Force (IETF) at . Subscription address is . Discussions of the group are archived at URL: http://www.acl.lanl.gov/HTML_WG/archives.html. Abstract The Hypertext Markup Language (HTML) is a simple markup language used to create hypertext documents that are platform independent. Ini- tially, the application of HTML on the World Wide Web was seriously restricted by its reliance on the ISO-8859-1 coded character set, which is appropriate only for Western European languages. Despite this restriction, HTML has been widely used with other languages, using other coded character sets or character encodings, at the expense of interoperability. This document is meant to address the issue of the Expires 18 August 1996 [Page 1] Internet Draft HTML internationalization 13 February 1996 internationalization of HTML by extending the specification of HTML and giving additional recommendations for proper internationalisation support. A foremost consideration is to make sure that HTML remains a valid application of SGML, while enabling its use in all languages of the world. Table of contents 1. Introduction .................................................. 2 1.1. Scope ...................................................... 3 1.2. Conformance ................................................ 3 2. The document character set ..................................... 4 2.1. Reference processing model ................................. 4 2.2. The document character set ................................. 6 2.3. Undisplayable characters ................................... 7 3. The LANG attribute.............................................. 7 4. Additional entities, attributes and elements ................... 9 4.1. Full Latin-1 entity set .................................... 9 4.2. Markup for language-dependent presentation ................. 9 5. Forms ..........................................................11 5.1. DTD additions ..............................................11 5.2. Form submission ............................................12 6. Miscellaneous ..................................................13 7. HTML public text ...............................................15 7.1. HTML DTD ...................................................15 7.2. SGML declaration for HTML ..................................30 7.3. ISO Latin 1 character entity set ...........................31 Bibliography ......................................................34 Authors' Addresses ................................................36 1. Introduction The Hypertext Markup Language (HTML) is a simple markup language used to create hypertext documents that are platform independent. Ini- tially, the application of HTML on the World Wide Web was seriously restricted by its reliance on the ISO-8859-1 coded character set, which is appropriate only for Western European languages. Despite this restriction, HTML has been widely used with other languages, using other coded character sets or character encodings, through var- ious ad hoc extensions to the language [TAKADA]. This document is meant to address the issue of the internationaliza- tion of HTML by extending the specification of HTML and giving addi- tional recommendations for proper internationalisation support. It is in good part based on a paper by one of the authors on multilin- gualism on the WWW [NICOL]. A foremost consideration is to make sure Expires 18 August 1996 [Page 2] Internet Draft HTML internationalization 13 February 1996 that HTML remains a valid application of SGML, while enabling its use in all languages of the world. The specific issues addressed are the SGML document character set to be used for HTML, the proper treatment of the charset parameter asso- ciated with the "text/html" content type and the specification of language tags and additional entities. 1.1 Scope HTML has been in use by the World-Wide Web (WWW) global information initiative since 1990. This specification extends the capabilities of HTML (RFC 1866), primarily by removing the restriction to the ISO-8859-1 coded character set [ISO-8859-1]. HTML is an application of ISO Standard 8879:1986, Information Pro- cessing Text and Office Systems -- Standard Generalized Markup Lan- guage (SGML) [ISO-8879]. The HTML Document Type Definition (DTD) is a formal definition of the HTML syntax in terms of SGML. This specifi- cation amends the DTD of HTML in order to make it applicable to docu- ments encompassing a character repertoire much larger than that of ISO-8859-1, while still remaining SGML conformant. 1.2 Conformance This specification changes slightly the conformance requirements of HTML documents and HTML user agents. 1.2.1 Documents All HTML 2.0 conforming documents remain conforming with this speci- fication. However, the extensions introduced here make valid cer- tains documents that would not be HTML 2.0 conforming, in particular those containing characters or character references outside of the repertoire of ISO 8859-1, and those containing markup introduced herein. 1.2.2. User agents In addition to the requirements of RFC 1866, the following require- ments are placed on HTML user agents. To ensure interoperability and proper support for at least ISO-8859-1 in an environment where character encoding schemes other than ISO-8859-1 are present, user agents must correctly interpret the charset parameter accompanying an HTML document Expires 18 August 1996 [Page 3] Internet Draft HTML internationalization 13 February 1996 received from the network. Furthermore, conforming user-agents are required to at least parse correctly all numeric character references within the range of the Basic Multilingual Plane (BMP) of ISO 10646-1 [ISO-10646]. 2. The document character set 2.1. Reference processing model This overview explains a reference processing model used for HTML, and in particular the SGML concept of a document character set. An actual implementation may widely differ in its internal workings from the model given below, but should behave as described to an outside observer. Because there are various widely differing encodings of text, SGML does not directly address the question of how characters are encoded e.g. in a file. SGML views the characters as a single set (called a "character repertoire"), and a "code set" that assigns an integer number (known as "character number") to each character in the reper- toire. The document character set declaration defines what each of the character numbers represents [GOLD90, p. 451]. In most cases, an SGML DTD and all documents that refer to it have a single document character set, and all markup and data characters are part of this set. HTML, as an application of SGML, does not directly address the ques- tion of how characters are encoded as octets in external representa- tions such as files. This is deferred to mechanisms external to HTML, such as MIME as used by the HTTP protocol or by electronic mail. For the HTTP protocol [HTTP-1.0], the way characters are encoded is defined by the "charset" parameter [1] of the "Content-Type" field of the header of an HTTP response. For example, to indicate that the transmitted document is encoded in the "JIS" encoding of Japanese [RFC1468], the header will contain the following line: Content-Type: text/html; charset=ISO-2022-JP _________________________ [1] The term "charset" in MIME is used to designate a character encoding, rather than a coded character set as the term may suggest. A character encoding is a mapping (possibly many-to-one) of a sequence of octets to a sequence of characters taken from one or more character repertoires. Expires 18 August 1996 [Page 4] Internet Draft HTML internationalization 13 February 1996 The default charset parameter in the case of the HTTP protocol is ISO-8859-1 (the so-called "Latin-1" for Western European characters). The HTTP protocol also defines a mechanism for the client to specify the character encodings it can accept. Clients and servers are strongly requested to use these mechanisms to assure correct trans- mission and interpretation of any document. Provisions that can be taken to help correct interpretation, even in cases where a server or client do not yet use these mechanisms, are described in section 6. Similarly, if HTML documents are transferred by electronic mail, the character encoding is defined by the "charset" parameter of the "Con- tent-Type" MIME header line [RFC1521]. In the case any other way of transferring and storing HTML documents are defined or become popular, it is advised that similar provisions should be made to clearly identify the character encoding used and/or to use a single/default encoding capable of representing the widest range of characters used in an international context. Whatever the external character encoding actually be, the reference processing model translates it to a representation of the document character set specified in Section 2.2 before processing specific to SGML/HTML. The reference processing model can be depicted as fol- lows: [resource]->[decoder]->[entity ]->[ SGML ]->[application]->[display] [manager] [parser] ^ | | | +----------+ The decoder is responsible for decoding the external representation of the resource to a representation using the document character set. The entity manager, the parser, and the application deal only with characters of the document character set. A display-oriented part of the application or the display machinery itself may again convert characters represented in the document character set to some other representation more suitable for their purpose. In any case, the entity manager, the parser, and the application, as far as character semantics are concerned, are using the HTML document character set only. An actual implementation may choose, or not, to translate the docu- ment into some encoding of the document character set as described above; the behaviour described by this reference processing model can be achieved otherwise. This subject is well out of the scope of this specification, however, and the reader is invited to consult the SGML standard [ISO-8879] or a SGML handbook [BRYAN88] [GOLD90] [VANH90] Expires 18 August 1996 [Page 5] Internet Draft HTML internationalization 13 February 1996 [SQ91] for further information. The most important consequence of this reference processing model is that numeric character references are always resolved with respect to the fixed document character set, and thus to the same characters, whatever the external encoding actually used. For an example, see Section 2.2. 2.2. The document character set The document character set, in the SGML sense, is the Basic Multilin- gual Plane of ISO 10646:1993 [ISO-10646], also known as UCS-2. This is code-by-code identical with the Unicode standard [UNICODE]. The adoption of this document character set implies a change in the SGML declaration specified in the HTML 2.0 specification (section 9.5 of [RFC1866]). The change amounts to removing the two BASESET specifi- cations and their accompanying DESCSET declarations, replacing them with the following declaration: BASESET "ISO Registration Number 176//CHARSET ISO/IEC 10646-1:1993 UCS-2 with implementation level 3 //ESC 2/5 2/15 4/5" DESCSET 0 9 UNUSED 9 2 9 11 2 UNUSED 13 1 13 14 18 UNUSED 32 95 32 127 1 UNUSED 128 32 UNUSED 160 65374 160 Making UCS-2 the document character set does not create non- conformance of any expression, construct or document that is conform- ing to HTML 2.0. It does make conforming certain constructs that are not admissible in HTML 2.0. One consequence is that data characters outside the repertoire of ISO-8859-1, but within that of UCS-2 become valid SGML characters. Another is that the upper limit of the range of numeric character references is extended from 255 to 65533 [2] ; thus, И is a valid reference to a "CYRILLIC CAPITAL LETTER I". [ERCS] is a good source of information on Unicode and SGML, although _________________________ [2] 65533 (FFFD hexadecimal) is the last valid char- acter in UCS-2. 65534 (FFFE hexadecimal) is unassigned and reserved as the byte-swapped version of ZERO WIDTH NON-BREAKING SPACE for byte-sex detection purposes. 65535 (FFFF hexadecimal) is unassigned. Expires 18 August 1996 [Page 6] Internet Draft HTML internationalization 13 February 1996 its scope and technical content differ greatly from this specifica- tion. ISO 10646-1:1993 is the most encompassing character set currently existing, and there is no other character set that could take its place as the document character set for HTML. Also, it is expected that with future extensions of ISO 10646, this specification may also be extended. If nevertheless for a specific application there is a need to use characters outside this standard, this should be done by avoiding any conflicts with present or future versions of ISO 10646, i.e. by assigning these characters to a private zone. Also, it should be borne in mind that such a use will be highly unportable; in many cases, it may be better to use inline bitmaps. 2.3. Undisplayable characters With the document character set being the full ISO 10646 BMP, the possibility that a character cannot be displayed due to lack of appropriate resources (fonts) cannot be avoided. Because there are many different things that can be done in such a case, this document does not prescribe any specific behaviour. Depending on the implemen- tation, this may also be handled by the underlaying display system and not the application itself. The following considerations, how- ever, may be of help: - A clearly visible, but unobtrusive behaviour should be preferred. Some documents may contain many characters that cannot be renden- dered, and so showing an alert for each of them is not the right thing to do. - In case a numeric representation of the missing character is given, its hexadecimal (not decimal) form is to be preferred, because this form is used in character set standards [ERCS]. 3. The LANG attribute Language tags can be used to control rendering of a marked up docu- ment in various ways: character disambiguation, in cases where the character encoding is not sufficient to resolve to a specific glyph; quotation marks; hyphenation; ligatures; spacing; voice synthesis; etc. Independently of rendering issues, language markup is useful as content markup for purposes such as classification and searching. Since any text can logically be assigned a language, almost all HTML elements admit the LANG attribute. The DTD reflects this. It is also intended that any new element introduced in later versions of HTML will admit the LANG attribute, unless there is a good reason not to do so. Expires 18 August 1996 [Page 7] Internet Draft HTML internationalization 13 February 1996 The language attribute, LANG, takes as its value a language tag that identifies a natural language spoken, written, or otherwise conveyed by human beings for communication of information to other human beings. Computer languages are explicitly excluded. The syntax and registry of HTML language tags is the same as that defined by RFC 1766 [RFC1766]. In summary, a language tag is composed of one or more parts: A primary language tag and a possibly empty series of subtags: language-tag = primary-tag *( "-" subtag ) primary-tag = 1*8ALPHA subtag = 1*8ALPHA Whitespace is not allowed within the tag and all tags are case- insensitive. The namespace of language tags is administered by the IANA. Example tags include: en, en-US, en-cockney, i-cherokee, x-pig-latin Two-letter primary-tags are reserved for ISO 639 language abbrevia- tions [ISO-639], and three-letter primary-tags for the language abbreviations of the "Ethnologue" [ETHNO] (the latter is in addition to the requirements of RFC 1766). Any two-letter initial subtag is an ISO 3166 country code [ISO-3166]. In the context of HTML, a language tag is not to be interpreted as a single token, as per RFC 1766, but as a hierarchy. For example, a user agent that adjusts rendering according to language should con- sider that it has a match when a language tag in a style sheet entry matches the initial portion of the language tag of an element. An exact match should be preferred. This interpretation allows an ele- ment marked up as, for instance, "en-US" to trigger styles corre- sponding to, in order of preference, US-English ("en-US") or 'plain' or 'international' English ("en"). NOTE -- using the language tag as a hierarchy does not imply that all languages with a common prefix will be understood by those fluent in one or more of those lan- guages; it simply allows the user to request this commonal- ity when it is true for that user. The rendering of elements may be affected by the LANG attribute. For any element, the value of the LANG attribute overrides the value specified by the LANG attribute of any enclosing element and the value (if any) of the HTTP Content-Language header. If none of these are set, a suitable default, perhaps controlled by user preferences, by automatic context analysis or by the user's locale, should be used Expires 18 August 1996 [Page 8] Internet Draft HTML internationalization 13 February 1996 to control rendering. 4. Additional entities, attributes and elements 4.1. Full Latin-1 entity set According to the suggestion of section 14 of [RFC1866], the set of Latin-1 entities is extended to cover the whole right part of ISO-8859-1 (all code positions with the high-order bit set). The names of the entities are taken from the appendices of [SGML]. A list is provided in section 7.3 of this specification. 4.2. Markup for language-dependent presentation For the correct presentation of text from certain languages (irre- spective of formatting issues), some support in the form of addi- tional entities and elements is needed. Markup is needed in some cases to force or block joining behavior in contexts in which joining would occur but should not or would not occur but should. Many languages are written in horizontal lines from left to right, while others are written from right to left. When both writing directions are present, one talks of bidirectional text (BIDI for short). BIDI text requires markup in special circumstances where ambiguities as to the directionality of some characters have to be resolved. This markup affects the ability to render BIDI text in a semantically legible fashion. That is, without this special BIDI markup, cases arise which would prevent *any* rendering whatsoever that reflected the basic meaning of the text. Plain text may contain this markup (joining or BIDI) in the form of special-purpose charac- ters; in HTML, these are replaced by SGML markup as follows: First, a generic container is needed to carry the LANG and DIR (see below) attributes in cases where no other element is appropriate; the SPAN element is introduced for that purpose. A set of named character entities is added that allows partial sup- port of the Unicode bidirectional algorithm [UNICODE], plus some help with languages requiring contextual analysis for rendering: Next, an attribute called DIR is introduced, restricted to the values LTR (left-to-right) and RTL (right-to-left) and admitted by most ele- ments. On block-type elements, the DIR attribute indicates the base Expires 18 August 1996 [Page 9] Internet Draft HTML internationalization 13 February 1996 directionality of the text in the block; if omitted it is inherited from the parent element. On inline elements, it makes the element start a new embedding level (to be explained below); if omitted the inline element does not start a new embedding level. Lastly, a new element called BDO (BIDI override) is introduced, which requires the DIR attribute to specify whether the override is left- to-right or right-to-left. Its effect is to force the directionality of all characters within it to the value of DIR, irrespective of their intrinsic directional properties. The zero-width joiner and non-joiner (‍ and ‌) are used to control joining behaviour. For example, ARABIC LETTER HEH is used in isolation to abbreviate "Hijri" (the Islamic calendrical system); however, the initial form of the letter is desired, because the iso- lated form of HEH looks like the digit five as employed in Arabic script. This is obtained by following the HEH with a zero-width joiner whose only effect is to provide context. In Persian texts, there are cases where a letter that normally would join a subsequent letter in a cursive connection does not. Here a zero-width non- joiner is used. The left-to-right and right-to-left marks (‎ and ‏) are used to disambiguate directionality of neutral characters, e.g., if you have a double quote sitting between an Arabic and a Latin letter, then which direction does the quote resolve to? These characters are like zero width spaces which have a directional property (but no word/line break property). Nested embeddings of contra-directional text runs is also a case where the implicit directionality of characters is not sufficient, requiring markup. A common need for the embedding controls is to han- dle text that has been pasted from one bidi context to another, and the possibility of multiply embedded pastings. Following is an exam- ple of a case where embedding is needed, showing its effect: Given the following latin (upper case) and arabic (lower case) letters in backing store with the specified embed- dings: AB xy CD zw EF One gets the following rendering (with [] showing the directional transitions): [ AB [ wz [ CD ] yx ] EF ] Expires 18 August 1996 [Page 10] Internet Draft HTML internationalization 13 February 1996 On the other hand, without this markup and with a base direction of LTR one gets the following rendering: [ AB [ yx ] CD [ wz ] EF ] Notice that yx is on the left and wz on the right unlike the above case where the embedding levels are used. With- out the embedding markup one has at most two levels: a base directional level and a single counterflow directional level. The directional override feature ()is needed to deal with unusual pieces of text in which directionality cannot be resolved from context in an unambiguous fashion. For example, it can be used to force left-to-right (or right-to-left) display of part numbers composed of Latin letters, digits and Hebrew letters. A few other additional elements are important to have for proper lan- guage-dependent rendering. Short quotations, and in particular the quotation marks surrounding them, are typically rendered differently in different languages and on platforms with different graphic capabilities: "a quotation in English", `another, slightly better one', ,,a quotation in German'', << a quotation in French >>. The element is introduced for that purpose. Many languages require superscripts for proper rendering: as an exam- ple, the French "Mlle Dupont" should have "lle" in superscript. The element, and its sibling , are introduced to allow proper markup of such text. and contents are restricted to PCDATA to avoid nesting problems. Finally, in many languages text justification is much more important than it is in Western languages, and justifies markup. The ALIGN attribute, admitting values of LEFT, RIGHT, CENTER and JUSTIFY, is added to a selection of elements where it makes sense (block-like). 5. Forms 5.1. DTD additions It is natural to expect input in any language in forms, as they pro- vide one of the only ways of obtaining user input. While this is pri- marily a UI issue, there are some things that should be specified at the HTML level to guide behavior and promote interoperability. Expires 18 August 1996 [Page 11] Internet Draft HTML internationalization 13 February 1996 To ensure full interoperability, it is necessary for the user agent (and the user) to have an indication of the character encoding(s) that the server providing a form will be able to handle upon submis- sion of the filled-in form. Such an indication is provided by the ACCEPT-CHARSET attribute of the INPUT and TEXTAREA elements, modeled on the HTTP Accept-Charset header (see [HTTP-1.1]), which contains a space and/or comma delimited list of character sets acceptable to the server. A user agent may want to somehow advise the user of the con- tents of this attribute, or to restrict his possibility to enter characters outside the repertoires of the listed character sets. NOTE -- The list of character sets is to be interpreted as an EXCLUSIVE-OR list; the server announces that it is ready to accept any ONE of these character encoding schemes for each part of a multipart entity. The client may perform character encoding translation to satisfy the server if necessary. NOTE -- The default value for the ACCEPT-CHARSET attribute of an INPUT or TEXTAREA element is the reserved value "UNKNOWN". A user agent may interpret that value as the character encoding scheme that was used to transmit the document containing that element. 5.2. Form submission The HTML 2.0 form submission mechanism, based on the "application/x- www-form-urlencoded" media type, is ill-equipped with regard to internationalization. In fact, since URLs are restricted to ASCII characters, the mechanism is akward even for ISO-8859-1 text. Sec- tion 2.2 of [RFC1738] specifies that octets may be encoded using the "%HH" notation, but text submitted from a form is composed of charac- ters, not octets. Lacking a specification of a character encoding scheme, the "%HH" notation has no well-defined meaning. A partial solution to this sorry state of affairs is to specify a default character encoding scheme to be assumed when the GET method of form submission is used. Specifying UCS-2 would break all exist- ing forms, so the only sensible way is to designate ISO-8859-1. That is, the encoded URL sent to submit a form by the GET method is to be interpreted as a sequence of single-octet characters encoded accord- ing to ISO-8859-1, and further encoded according to the scheme of [RFC1738] (the "%HH" notation). This is clearly insufficient, so designers of forms are advised to use the POST method of form submis- sion whenever possible. A better solution is to add a MIME charset parameter to the Expires 18 August 1996 [Page 12] Internet Draft HTML internationalization 13 February 1996 "application/x-www-form-urlencoded" media type specifier sent along with a POST method form submission, with the understanding that the URL encoding of [RFC1738] is applied on top of the specified charac- ter encoding, as a kind of implicit Content-Transfer-Encoding. The default ISO-8859-1 is implied in the absence of a charset parameter. The best solution is to use the "multipart/form-data" media type described in [RFC1867] with the POST method of form submission. This mechanism encapsulates the value part of each name-value pair in a body-part of a multipart MIME body that is sent as the HTTP entity; each body part can be labeled with an appropriate Content-Type, including if necessary a charset parameter that specifies the charac- ter encoding scheme. The changes to the DTD necessary to support this method of form submission have been incorporated in the DTD included in this specification. How the user agent determines the encoding of the text entered by the user is outside the scope of this specification. NOTE -- Designers of forms and their handling scripts should be aware of an important caveat: when the default value of a field (the VALUE attribute) is returned upon form submission (i.e. the user did not modify this value), it cannot be guaranteed to be transmitted as a sequence of octets identical to that in the source document -- only as a possibly different but valid encoding of the same sequence of characters. This may be true even if the encoding of the document con- taining the form and that used for submission are the same, because only the sequence of characters of the default value, not the actual sequence of octets, may be counted on to be preserved. 6. Miscellaneous Proper interpretation of a text document requires that the character encoding scheme be known. Current HTTP servers, however, do not gen- erally include an appropriate charset parameter with the Content-Type header, even when the encoding scheme is different from the default ISO-8859-1. This is bad behaviour [3] , and as such strongly _________________________ [3] This bad behaviour is even encouraged by the con- tinued existence of browsers that declare an unrecog- nized media type when they receive a charset parameter. User agent implementators are strongly encouraged to make their software tolerant of this parameter, even if they cannot take advantage of it. Expires 18 August 1996 [Page 13] Internet Draft HTML internationalization 13 February 1996 discouraged, but some preventive measures can be taken to minimize the detrimental effects. In the case where a document is accessed from a hyperlink in an ori- gin HTML document, a CHARSET attribute is added to the attribute list of elements with link semantics (A and LINK), specifically by adding it to the linkExtraAttributes entity. The value of that attribute is to be considered a hint to the User Agent as to the character encod- ing scheme used by the ressource pointed to by the hyperlink; it should be the appropriate value of the MIME charset parameter for that ressource. In any document, it is possible to include an indication of the encoding scheme like the following, as early as possible within the HEAD of the document: This is not foolproof, but will work if the encoding scheme is such that ASCII characters stand for themselves at least until the META element is parsed. Note that there are better ways for a server to obtain character encoding information, instead of the unreliable above; see [NICOL2] for some details and a proposal. For definiteness, the "charset" parameter received from the source of the document should be considered the most authoritative, followed in order of preference by the contents of a META element such as the above, and finally the CHARSET parameter of the anchor that was fol- lowed (if any). When HTML text is transmitted directly in UCS-2 (charset=UNICODE-1-1), the question of byte order arises: does the high-order byte of each two-byte character come first or second? For definiteness, this specification recommends that UCS-2 be transmitted in big-endian byte order (high order byte first), which corresponds to the established network byte order for two-byte quantities, to the Unicode recommendation for serialized text data and to RFC 1641. Furthermore, to maximize chances of proper interpretation, it is rec- ommended that documents transmitted as UCS-2 always begin with a ZERO-WIDTH NON-BREAKING SPACE character (hexadecimal FEFF) which, when byte-reversed becomes number FFFE, a character guaranteed to be never assigned. Thus, a user-agent receiving an FFFE as the first octets of a text would know that bytes have to be reversed for the remainder of the text. There exist so-called UCS Transformation Formats than can be used to transmit UCS data, in addition to UCS-2. UTF-7 [RFC1642] and UTF-8 Expires 18 August 1996 [Page 14] Internet Draft HTML internationalization 13 February 1996 [UTF-8] have interesting properties (no byte-ordering problem, dif- ferent flavours of ASCII compatibility) that make them worthy of con- sideration, especially for transmission of multilingual text. The UTF-1 transformation format of ISO 10646 (registered by IANA as ISO-10646-UTF-1), has been removed from ISO 10646, and should not be used. 7. HTML Public Text 7.1. HTML DTD This section contains a DTD for HTML based on the HTML 2.0 DTD of RFC 1866, incorporating the changes for file upload as specified in RFC 1867, and the changes deriving from this document. ... -- > ]]> %ISOlat1; ]]> Expires 18 August 1996 [Page 18] Internet Draft HTML internationalization 13 February 1996 Expires 18 August 1996 [Page 19] Internet Draft HTML internationalization 13 February 1996 Heading is preferred to

Heading

--> ]]> " > #AttVal(Alt)" > ]]> ]]> ]]> Directory" > Menu" > Heading

Text ... is preferred to

Heading

Text ... --> ]]> Form:" %SDASUFF; "Form End." > Select #AttVal(Multiple)" > ]]> ]]> " > Expires 18 August 1996 [Page 28] Internet Draft HTML internationalization 13 February 1996 [Document is indexed/searchable.]"> ]]> Expires 18 August 1996 [Page 29] Internet Draft HTML internationalization 13 February 1996 7.2. SGML Declaration for HTML 7.3. ISO Latin 1 entity set The following public text lists each of the characters specified in the Added Latin 1 entity set, along with its name, syntax for use, Expires 18 August 1996 [Page 31] Internet Draft HTML internationalization 13 February 1996 and description. This list is derived from ISO Standard 8879:1986//ENTITIES Added Latin 1//EN. HTML includes the entire entity set, and adds entities for all missing characters in the right part of ISO-8859-1. Expires 18 August 1996 [Page 32] Internet Draft HTML internationalization 13 February 1996 Expires 18 August 1996 [Page 33] Internet Draft HTML internationalization 13 February 1996 Bibliography [BRYAN88] M. Bryan, "SGML -- An Author's Guide to the Standard Generalized Markup Language", Addison-Wesley, Reading, 1988. [ERCS] Extended Reference Concrete Syntax for SGML. [ETHNO] "Ethnologue, Languages of the World", 12th Edition, Barbara F. Grimes, editor, Summer Institute of Lin- guistics, Dallas, 1992. [GOLD90] C. F. Goldfarb, "The SGML Handbook", Y. Rubinsky, Ed., Oxford University Press, 1990. [HTTP-1.0] T. Berners-Lee, R.T. Fielding, and H. Frystyk Nielsen, "Hypertext Transfer Protocol -- HTTP/1.0", Work in progress (draft-ietf-http-v10-spec-04.txt), MIT/LCS, UC Irvine, October 1995. [HTTP-1.1] R.T. Fielding, H. Frystyk Nielsen, and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", Work in progress (draft-ietf-http-v11-spec-01.txt), MIT/LCS, January 1996. [ISO-639] ISO 639:1988. Codes pour la représentation des noms de langue. Technical content in Expires 18 August 1996 [Page 34] Internet Draft HTML internationalization 13 February 1996 [ISO-3166] ISO 3166:1993. Codes pour la représentation des noms de pays. [ISO-8601] ISO 8601:1988. Éléments de données et formats d'échange -- Échange d'information -- Représentation de la date et de l'heure. [ISO-8859-1] ISO 8859-1:1987. International Standard -- Informa- tion Processing -- 8-bit Single-Byte Coded Graphic Character Sets -- Part 1: Latin Alphabet No. 1. [ISO-8879] ISO 8879:1986. International Standard -- Information Processing -- Text and Office Systems -- Standard Gen- eralized Markup Language (SGML). [ISO-10646] ISO/IEC 10646-1:1993. International Standard -- Infor- mation technology -- Universal Multiple-Octet Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane. [NICOL] G.T. Nicol, "The Multilingual World Wide Web", Elec- tronic Book Technologies, 1995, [NICOL2] G.T. Nicol, "MIME Header Supplemented File Type", Work in progress, , EBT, October 1995. [RFC1468] J. Murai, M. Crispin and E. van der Poel, "Japanese Character Encoding for Internet Messages", RFC 1468, Keio University, Panda Programming, June 1993. [RFC1521] N. Borenstein and N. Freed, "MIME (Multipurpose Inter- net Mail Extensions) Part One: Mechanisms for Specify- ing and Describing the Format of Internet Message Bod- ies", RFC 1521, Bellcore, Innosoft, September 1993. [RFC1590] J. Postel, "Media Type Registration Procedure", RFC 1590, USC/ISI, March 1994. [RFC1641] D. Goldsmith, M.Davis, "Using Unicode with MIME", RFC 1641, Taligent inc., July 1994. [RFC1642] D. Goldsmith, M. Davis, "UTF-7: A Mail-safe Transfor- mation Format of Unicode", RFC 1642, Taligent inc., July 1994. [RFC1738] T. Berners-Lee, L. Masinter, and M. McCahill, "Uniform Expires 18 August 1996 [Page 35] Internet Draft HTML internationalization 13 February 1996 Resource Locators (URL)", RFC 1738, CERN, Xerox PARC, University of Minnesota, October 1994. [RFC1766] H. Alverstrand, "Tags for the Identification of Lan- guages", RFC 1766, UNINETT, March 1995. [RFC1866] T. Berners-Lee and D. Connolly, "Hypertext Markup Lan- guage - 2.0", RFC 1866, MIT/W3C, November 1995. [RFC1867] E. Nebel and L. Masinter, "Form-based File Upload in HTML", RFC 1867, Xerox Corporation, November 1995. August 1995. [SQ91] SoftQuad, "The SGML Primer", 3rd ed., SoftQuad Inc., 1991. [TAKADA] Toshihiro Takada, "Multilingual Information Exchange through the World-Wide Web", Computer Networks and ISDN Systems, Vol. 27, No. 2, Nov. 1994 , p. 235-241. [TEI] TEI Guidelines for Electronic Text Encoding and Inter- change. [UNICODE] The Unicode Consortium, "The Unicode Standard -- Worldwide Character Encoding -- Version 1.0", Addison- Wesley, Volume 1, 1991, Volume 2, 1992. The BIDI algorithm is in appendix A of volume 1, with correc- tions in appendix D of volume 2. [UTF-8] X/Open Company Ltd., "File System Safe UCS Transforma- tion Format (FSS_UTF)", X/Open Preleminary Specifica- tion, Document Number P316. Also published in Unicode Technical Report #4 and soon in an annex to ISO 10646-1. [VANH90] E. van Hervijnen, "Practical SGML", Kluwer Academicq Publishers Group, Norwell and Dordrecht, 1990. Authors' Addresses François Yergeau Alis Technologies 100, boul. Alexis-Nihon Suite 600 Montréal QC H4M 2P2 Canada Tel: +1 (514) 747-2547 Expires 18 August 1996 [Page 36] Internet Draft HTML internationalization 13 February 1996 Fax: +1 (514) 747-2561 EMail: fyergeau@alis.com Gavin Thomas Nicol Electronic Book Technologies, Japan 1-29-9 Tsurumaki, Setagaya-ku, Tokyo Japan Tel: +81-3-3230-8161 Fax: +81-3-3230-8163 EMail: gtn@ebt.com, gtn@twics.co.jp Glenn Adams Stonehand 118 Magazine Street Cambridge, MA 02139 U.S.A. Tel: +1 (617) 864-5524 Fax: +1 (617) 864-4965 EMail: glenn@stonehand.com Martin J. Duerst Multimedia-Laboratory Departement of Computer Science University of Zurich Winterthurerstrasse 190 CH-8057 Zurich Switzerland Tel: +41 1 257 43 16 Fax: +41 1 363 00 35 E-mail: mduerst@ifi.unizh.ch Expires 18 August 1996 [Page 37]