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Network Working Group F. Yergeau Internet Draft G. Nicol <draft-ietf-html-i18n-00.txt> G. Adams Expires 20 February 1996 M. Duerst 15 August 1995 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 <html-wg@oclc.org>. 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. Up to the present time, the application of HTML on the World Wide Web was seriously restricted by its reliance on the ISO-8859-1 coded charac- ter set, which is appropriate only for Western European languages. Despite this restriction, HTML has been widely used with other lan- guages, using other coded character sets or character encodings, through various ad hoc extensions to the language. This document is meant to address the issue of the internationaliza- tion of HTML by extending the specification of HTML 2.0 and giving Expires 20 February 1996 [Page 1] Internet Draft HTML internationalization 15 August 1995 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. The "text/html; version=2.x" Internet Media Type [RFC1590] and MIME Content Type [RFC1521] is defined by this specification, taken together with the HTML 2.0 specification [HTML-2]. Table of contents 1. Introduction .................................................. 2 1.1. Scope ...................................................... 3 1.2. Conformance ................................................ 3 2. The document character set ..................................... 5 2.1. Reference processing model ................................. 5 2.2. The HTML 2.x document character set ........................ 7 2.3. Undisplayable characters ................................... 8 3. Language tags .................................................. 8 4. Additional entities and elements ...............................10 4.1. Full Latin-1 entity set ....................................10 4.2. Date, time, measures and monetary amounts ..................10 4.3. Entities and elements for language-dependent presentation ..12 5. Forms ..........................................................15 5.1. DTD additions ..............................................15 5.2. Form submission ............................................17 6. Miscellaneous ..................................................17 7. HTML public text ...............................................18 7.1. HTML DTD ...................................................18 7.2. SGML declaration for HTML ..................................34 7.3. Entity sets ................................................36 7.3.1. ISO Latin 1 character entity set .......................36 7.3.2. BIDI entity set ........................................39 Bibliography ......................................................39 Authors' Addresses ................................................41 1. Introduction The Hypertext Markup Language (HTML) is a simple markup language used to create hypertext documents that are platform independent. Up to the present time, the application of HTML on the World Wide Web was seriously restricted by its reliance on the ISO-8859-1 coded charac- ter set, which is appropriate only for Western European languages. Despite this restriction, HTML has been widely used with other lan- guages, using other coded character sets or character encodings, through various ad hoc extensions to the language [TAKADA]. Expires 20 February 1996 [Page 2] Internet Draft HTML internationalization 15 August 1995 This document is meant to address the issue of the internationaliza- tion of HTML by extending the specification of HTML 2.0 and giving additional recommendations for proper internationalisation support. It is in good part based on a paper by one of the authors on multi- lingualism on the WWW [NICOL]. 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. 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 2.0 (RFC xxx), primarily by removing the restriction to the ISO-8859-1 coded character set [ISO-8859-1]. Together with the HTML 2.0 specification, it defines a new version of HTML to be known as "HTML 2.x". 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 2.0 in order to make it applicable to documents encompassing a character repertoire much larger than that of ISO-8859-1, while still remaining SGML conformant. Together with the HTML 2.0, specification, this specification also defines HTML as an Internet Media Type [RFC1590] and MIME Content Type [RFC1521] called "text/html", or "text/html; version=2.x". As such, it defines the semantics of the HTML syntax and how that syntax should be interpreted by user agents. 1.2 Conformance This specification governs the syntax of HTML documents and aspects of the behavior of HTML user agents. 1.2.1 Documents A document is a conforming HTML document if: * It is a conforming SGML document, and it conforms to the HTML DTD Expires 20 February 1996 [Page 3] Internet Draft HTML internationalization 15 August 1995 (see 7.1, "HTML DTD"). * It conforms to the application conventions in this specification. For example, the value of the HREF attribute of the <A> element must conform to the URI syntax. 1.2.2. User agents An HTML user agent conforms to this specification if: * It parses the characters of an HTML document into data characters and markup according to SGML [ISO-8879]. NOTE -- In the interest of robustness and extensibility, there are a number of widely deployed conventions for han- dling non-conforming documents. See section 4.2.1 of the HTML 2.0 specification [HTML-2], "Undeclared Markup Error Handling" for details. * It supports at least the ISO-8859-1 character encoding scheme and processes each character in the ISO Latin Alphabet No. 1 as speci- fied in section 6.1 of [HTML-2]. 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 received from the network. Furthermore, conforming user-agents are required to at least parse correctly numeric character references outside the range of ISO-8859-1, but within that of UCS-2. NOTE -- To support non-western writing systems, HTML user agents are encouraged to support `ISO-10646-UCS-2' or simi- lar character encoding schemes and as much of the character repertoire of [ISO-10646] as is practical. * It behaves identically for documents whose parsed token sequences are identical. For example, comments and the whitespace in tags disappear during tokenization, and hence they do not influence the behavior of con- forming user agents. * It allows the user to traverse (or at least attempt to traverse, resources permitting) all hyperlinks from <A> elements in an HTML document. Expires 20 February 1996 [Page 4] Internet Draft HTML internationalization 15 August 1995 An HTML user agent is a level 2 user agent if, additionally: * It allows the user to express all form field values specified in an HTML document and to (attempt to) submit the values as requests to information services. 2. The document character set 2.1. Reference processing model This overview explains the reference processing model used for HTML 2.x, 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 out- side 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 the HTTP protocol, or MIME for electronic mail. For the HTTP protocol [HTTP], the way characters are encoded is defined by the "charset" parameter[1] added to 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 use of the keyword "charset" in MIME suggests that the corresponding parameter defines a character set in the terms used here. This is not true, the "charset" parameter actually specifies an encoding, i.e. the mapping of one (or several) character set(s) to octets. Expires 20 February 1996 [Page 5] Internet Draft HTML internationalization 15 August 1995 The default character set parameter in 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 define 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, it is always translated to a representation of the document character set speci- fied in Section 2.2 before processing specific to SGML/HTML. The reference processing model can be depicted as follows: [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 2.x document character set only. An actual implementation may choose to translate the document into some encoding of the document character set as described above. How- ever, the behaviour described by this reference processing model can be achieved otherwise, in particular by using scan-suppression tech- niques. 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] [SQ91] for Expires 20 February 1996 [Page 6] Internet Draft HTML internationalization 15 August 1995 further information. The most important consequence of this reference processing model is that numeric character references are always resolved to the same characters, whatever the external encoding actually used. For an example, see Section 2.2. 2.2. The HTML 2.x document character set The document character set, in the SGML sense, of HTML 2.x is the Basic Multilingual 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 specifica- tion (section 9.5 of [HTML-2]). The change amounts to removing the two BASESET specifications and their accompanying DESCSET declara- tions, 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 65376 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 its scope and technical content differ greatly from this _________________________ [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 20 February 1996 [Page 7] Internet Draft HTML internationalization 15 August 1995 specification. 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 2.x. 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 recommend 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. Language tags 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. 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 Expires 20 February 1996 [Page 8] Internet Draft HTML internationalization 15 August 1995 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 ISO CD 639-2 [ISO-CD-639-2] (the latter is in addi- tion 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. 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. For the cases where a word or phrase differs only by language from the surrounding text, an element is needed as a container. This ele- ment is called LANG, and admits the LANG attribute. The rendering of elements is meant to be controlled (in part) by the LANG attribute. Specific user preferences set within the browser Expires 20 February 1996 [Page 9] Internet Draft HTML internationalization 15 August 1995 should override the value of the LANG attribute, which in turn over- rides the value specified by the LANG attribute of any enclosing ele- ment. If none of these are set, a suitable default, perhaps con- trolled by the user's locale, should be used to control rendering. 4. Additional entities and elements 4.1. Full Latin-1 entity set According to the suggestion of section 14 of [HTML-2], the set of Latin-1 entities is extended to cover the whole right part of ISO-8859-1. The names of the entities are taken from the appendices of [SGML]. A list is provided in section 7.3.1 of this specifica- tion. 4.2. Date, time, measures and monetary amounts One problem that faces the Web is that of data representation. Given the date "12/9/95", many people will think that this represents the 12th of September, 1995, while many others will think it represents December 9th. The same problem arises for many other data forms. It is desireable that the Web have a culture-neutral format for data, so that browsers can display the data in the most appropriate format for the end user. However, taking away all presentation choice from the publishers is also a bad idea, hence, some way of supplying override- able presentation hints is also desireable. A set of elements are proposed below to address the above problem. DATE This is used to store dates in such a way that formatting can be decided upon by the browser. It is desirable that the document author be able to provide the default format, with the end-user making the final decision. This format- ting is decided upon by the combination, of the CALENDAR and LANG attributes. The declaration of the DATE element is: <!ELEMENT DATE - O #EMPTY> <!ATTLIST DATE %attrs; CALENDAR CDATA #IMPLIED --specify possible values? -- VALUE CDATA #REQUIRED > If the CALENDAR attribute is not specified, the Gregorian calendar should be assumed, in which case, the format for the value of the VALUE attribute should be in yyyy-mm-dd format, as per ISO 8601:1988 [ISO-8601]. Expires 20 February 1996 [Page 10] Internet Draft HTML internationalization 15 August 1995 TIME Like the DATE element, the TIME element is used to store time such that it is independent of geographical location, and formatting. The declaration of the TIME element is: <!ELEMENT TIME - O #EMPTY> <!ATTLIST TIME %attrs; ZONE CDATA #IMPLIED VALUE CDATA #REQUIRED > The contents of VALUE should be in hh:mm:ss.ss format. ZONE should contain a string representing the offset of the zone from GMT of the form "+HHMM" or "-HHMM". If omitted, Uni- versal Time (GMT) should be assumed. For example, <TIME ZONE="-0500" VALUE="11:35:04"> represents eleven hours thirty-five minutes and four seconds after midnight in Eastern North America, which is 16:35:04 GMT. MEASURE This element is designed to allow measurements to be marked up such that they can be converted between systems, and also to allow some formatting flexibility. The declaration of the MEASURE element is: <!ELEMENT MEASURE - O #EMPTY> <!ATTLIST MEASURE %attrs; TYPE (mass|length|area|volume|temp|dur) #REQUIRED UNIT CDATA #IMPLIED VALUE CDATA #REQUIRED > This is a variation of the TEI MEASURE element [TEI]. The TYPE attribute specifies the type of measurement being rep- resented. The UNIT attribute indicates the measurement unit type, and defaults to the applicable unit type from SI [ISO-1000] if not specified. The VALUE attribute specifies the amount of the unit. The contents of the VALUE unit should be parseable using the float_constant pattern from the following lex(1) definition: digit [0-9] exponent [eE][+-]?{digit}+ i {digit}+ float_constant[+-]?({i}|({i}.{i}?)|({i}?.{i})){exponent}? Expires 20 February 1996 [Page 11] Internet Draft HTML internationalization 15 August 1995 MONEY This element is designed to represent monetary amounts, such that conversion between systems and formatting varia- tions are possible. The definition of this element is: <!ELEMENT MONEY - O #EMPTY> <!ATTLIST MONEY %attrs; UNIT CDATA #REQUIRED VALUE CDATA #REQUIRED > The UNIT attribute specifies the currency unit, using the abbreviations of ISO 4217 [ISO-4217]. The VALUE attribute contains the amount, and should follow the lexical model of the VALUE attribute of the MEASURE element. It is conceiv- able that the functionality of this element could be made part of MEASURE. It should be noted that there are many special cases involving the representation of data. For example, many people in New Zealand still use miles, even though New Zealand has officially adopted the metric system. Worse, some people use miles when they mean kilometers. This proposal is not aimed at handling all such cases, but rather to pre- sent a reasonable balance between usability, and accuracy. When for- mat is of the utmost importance, these tags need not be used. 4.3. Entities and elements 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. In particular, bidirectional text (BIDI for short) requires markup in special circumstances where ambiguities as to the directionnality of some characters have to be resolved. First, a set of named character entities is added that allows full support of the Unicode bidirectional algorithm [UNICODE], plus some help with languages requiring contextual analysis for ren- dering: <!ENTITY zwnj SDATA "[zwnj ]"--=zero width non-joiner--> <!ENTITY zwj SDATA "[zwj ]"--=zero width joiner--> <!ENTITY lrm SDATA "[lrm ]"--=left-to-right mark--> <!ENTITY rlm SDATA "[rlm ]"--=right-to-left mark--> <!ENTITY lre SDATA "[lre ]"--=left-to-right embedding--> <!ENTITY rle SDATA "[rle ]"--=right-to-left embedding--> <!ENTITY pdf SDATA "[pdf ]"--=pop directional formatting--> <!ENTITY lro SDATA "[lro ]"--=left-to-right override--> <!ENTITY rlo SDATA "[rlo ]"--=right-to-left override--> Expires 20 February 1996 [Page 12] Internet Draft HTML internationalization 15 August 1995 These correspond to the following characters from ISO/IEC 10646-1:1993 (with the equivalent numeric character reference added at the right): 0x200C ZERO WIDTH NON-JOINER ‌ 0x200D ZERO WIDTH JOINER ‍ 0x200E LEFT-TO-RIGHT MARK ‎ 0x200F RIGHT-TO-LEFT MARK ‏ 0x202A LEFT-TO-RIGHT EMBEDDING ‪ 0x202B RIGHT-TO-LEFT EMBEDDING ‫ 0x202C POP DIRECTIONAL FORMATTING ‬ 0x202D LEFT-TO-RIGHT OVERRIDE ‭ 0x202E RIGHT-TO-LEFT OVERRIDE ‮ These entities affect the ability to render BIDI text in a semanti- cally legible fashion. That is, without these special BIDI charac- ters, cases arise which would prevent *any* rendering whatsoever that reflected the basic meaning of the text. It is for this reason that these special characters were added to Unicode (and, thence, to ISO/IEC 10646). If it were possible to do reliable layout and ren- dering of bidirectionnal text without them, they definitely would not have been included in Unicode (at least not the stateful characters: LRE, RLE, LRO, LRO, and PDF). They are needed for the following: 1. RTL MARK, LTR MARK - used to disambiguate directionality of directionally 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 direc- tional property (but no word/line break property). 2. ZWJ, ZWNJ - used to force or block joining behavior in contexts which joining would occur but should not or would not occur but should. For example, ARABIC LETTER HEH is used to abbreviate "Hijri" (the Islamic calendrical sys- tem); however, the isolated form of HEH looks like the digit five as employed in Arabic script (actually based on Indic digits). In order to prevent one from reading HEH as a final digit five in a year, the initial form of HEH is used. However, there is no following context (i.e., a joining letter) to which the HEH can join. Therefore, the ZWJ is used to provide that context. In Farsi texts, there are cases where a letter that normally would join a subse- quent letter in a cursive connection does not. Here the ZWNJ is used. 3. RTL EMBEDDING, LTR EMBEDDING is used to handle nested directional runs such as: Expires 20 February 1996 [Page 13] Internet Draft HTML internationalization 15 August 1995 Given the following latin/arabic letters in backing store with the specified embeddings: LRE L0 L1 RLE A0 A1 LRE L2 L3 PDF A2 A3 PDF L4 L5 PDF One gets the following rendering (with [] showing the directional transitions): [ L0 L1 [ A3 A2 [ L2 L3 ] A1 A0 ] L4 L5 ] On the other hand, without these characters, e.g., with L0 L1 A0 A1 L2 L3 A2 A3 L4 L5 and a base level of LTR one gets the following rendering: [ L0 L1 [ A1 A0 ] L2 L3 [ A3 A2 ] L4 L5 ] Notice that A1,A0 is on the left and A3,A2 on the right unlike the above case where the embedding levels are used. Without the embedding characters one has at most two lev- els: a base directional level and a single counterflow directional level. A common need for the embedding characters is to handle text that has been pasted from one bidi context to another and the possibility of multiply embedding pastings. 4. LTR OVERRIDE, RTL OVERRIDE - these are needed to deal with unusual pieces of text in which directionality cannot be resolved from context in an unambiguous fashion. For example, in part numbers, formulas, telephone numbers, and other similar pieces of text, it is difficult or impossible to derive the directionality of numbers, punctuation, and other neutrals from their context. To handle the case of the directional controls appearing directly in the text as coded characters, a new element, entities and SHORTREFS are defined: <!ELEMENT BIDI - - (%text)+> <!ATTLIST BIDI %attrs; DIR (ltr|rtl) #IMPLIED FORCE (gad|dag) #IMPLIED > The dir attribute corresponds to the 'embedding' entities (lre and Expires 20 February 1996 [Page 14] Internet Draft HTML internationalization 15 August 1995 rle), while the FORCE attribute corresponds to the 'override' ones (lro and rlo). Different allowed values of these attributes have to be used because of the quixotic semantics of SGML regarding tokens in name token groups. To support the occurrence of Unicode BIDI charac- ters in text (as coded characters), the following is defined: <!ENTITY lretag "<BIDI DIR=LTR>" > <!ENTITY rletag "<BIDI DIR=RTL>" > <!ENTITY lrotag "<BIDI FORCE=GAD>" > <!ENTITY rlotag "<BIDI FORCE=DAG>" > <!ENTITY pdftag "</BIDI>" > <!SHORTREF bidi "&#LRE;" lretag "&#RLE;" rletag "&#LRO;" lrotag "&#RLO;" rlotag "&#PDF;" pdftag > In this case LRE, RLE, LRO, RLO, and PDF have to be declared as func- tion names (mapped to the appropriate character numbers) in the SGML declaration's concrete syntax: FUNCTION LRE FUNCHAR 8234 -- LEFT-TO-RIGHT EMBEDDING -- RLE FUNCHAR 8235 -- RIGHT-TO-LEFT EMBEDDING -- PDF FUNCHAR 8236 -- POP DIRECTIONAL FORMATTING -- LRO FUNCHAR 8237 -- LEFT-TO-RIGHT OVERRIDE -- RLO FUNCHAR 8238 -- RIGHT-TO-LEFT OVERRIDE -- The above shortrefs and <BIDI> element allow dealing with existing text containing bidi controls, and doing so in the framework of marked up text. Another additional element is important to have for proper language- dependent rendering. Short quotations, and in particular the quota- tion marks surrounding them, are typically rendered differently in different languages and on platforms with different graphic capabili- ties: "a quotation in English", `another, slightly better one', ,,a quotation in German", << a quotation in French >>. The <Q> element is introduced for that purpose. 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 Expires 20 February 1996 [Page 15] Internet Draft HTML internationalization 15 August 1995 primarily a UI issue, there are some things that should be specified at the HTML level to guide behavior and promote interoperability. One is to add variants of the INPUT element corresponding to the ele- ments described in section 4.2, thus allowing locale-independent transmission of dates, times, etc. to a server. Specifically, DATE, TIME, MEASURE and MONEY are added as possible values of the TYPE attribute of the INPUT ELEMENT. Prior to transmission, the data should be converted to a canonical form, where possible. For example, if a user entered "24/12/1996" into a DATE field, it should be con- verted to "1996-12-24" when transmitted. Where this is not possible, information corresponding to the attributes of the elements defined need to be transmitted as well. This can be accomplished by expanding capabilities of the value part of the name-value pairs used to trans- mit forms data. The following syntax is recommended: forms-data = pair-list* pair-list = pair ";" pair-list | pair pair = name "=" value name = text value = simple-value | complex-value simple-value = text complex-value = "(" pair-list* ")" In complex-values, the name of the attribute is used as the name part of the name-value pair, "value" being the most common one.For exam- ple, a date might be transmitted as: date=(value=24/12/96;calendar=gregorian;lang=en-uk) suitably encoded. To ensure interoperability, it is necessary for the user agent (and the user) to have an indication of the character set(s) that the server providing a form will be able to handle upon submission of the filled-in form. Such an indication is provided by the ACCEPT-CHARSET attribute of the FORM element, modeled on the HTTP Accept-Charset header (see [HTTP]), 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 contents of this attribute, or to restrict his possibility to enter unacceptable characters. 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. Expires 20 February 1996 [Page 16] Internet Draft HTML internationalization 15 August 1995 5.2. Form submission The HTML 2.0 form submission mechanism, based on the "application/x- www-form-urlencoded" media type, is hopelessly broken with regard to internationalization. In fact, since URLs are restricted to ASCII characters, the mechanism is broken 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 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 the GET method of form submission is deprecated and should not be used in future documents, despite the language of section XX of [HTML-2]. A better solution is to add a MIME charset parameter to the Content- Type header sent along with a POST method form submission, with the understanding that the URL encoding of [RFC1738] is applied on top of the specified character encoding, as a kind of implicit Content- Transfer-Encoding. The default ISO-8859-1 is to be implied in the absence of a charset parameter. The best solution is to use the "multipart/form-data" media type described in [FILE-UPLOAD] 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. 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 Expires 20 February 1996 [Page 17] Internet Draft HTML internationalization 15 August 1995 ISO-8859-1. This is bad behaviour, and as such strongly 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 may be wise to include an indication of the encoding scheme like the following, as early as possible within the HEAD of the document: <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-2022-JP"> 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. 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). 7. HTML Public Text 7.1. HTML DTD  <!ENTITY % HTML.Version "-//IETF//DTD HTML 2.x//EN" -- Typical usage: Expires 20 February 1996 [Page 18] Internet Draft HTML internationalization 15 August 1995 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.x//EN"> <html> ... </html> -- >  <!ENTITY % HTML.Recommended "IGNORE" -- Certain features of the language are necessary for compatibility with widespread usage, but they may compromise the structural integrity of a document. This feature test entity enables a more prescriptive document type definition that eliminates those features. --> <![ %HTML.Recommended [ <!ENTITY % HTML.Deprecated "IGNORE"> ]]> <!ENTITY % HTML.Deprecated "INCLUDE" -- Certain features of the language are necessary for compatibility with earlier versions of the specification, but they tend to be used and implemented inconsistently, and their use is deprecated. This feature test entity enables a document type definition that eliminates these features. --> <!ENTITY % HTML.Highlighting "INCLUDE" -- Use this feature test entity to validate that a document uses no highlighting tags, which may be ignored on minimal implementations. --> <!ENTITY % HTML.Forms "INCLUDE" -- Use this feature test entity to validate that a document contains no forms, which may not be supported in minimal implementations --> <!ENTITY % HTML.Bidi "INCLUDE" -- Use this feature test entity to validate that a document does not use the BIDI element, entities and SHORTREFs, which may not be supported in some implementations Expires 20 February 1996 [Page 19] Internet Draft HTML internationalization 15 August 1995 -->  <!ENTITY % Content-Type "CDATA" -- meaning an internet media type (aka MIME content type, as per RFC1521) --> <!ENTITY % HTTP-Method "GET | POST" -- as per HTTP specification, in progress --> <!ENTITY % URI "CDATA" -- The term URI means a CDATA attribute whose value is a Uniform Resource Identifier. The syntax is defined by RFC 1808, "Relative Uniform Resource Locators." R. Fielding, June 1995 Note that CDATA attributes are limited by the LITLEN capacity (1024 in the current version of html.decl), so that URIs in HTML have a bounded length. -->  <!ENTITY % heading "H1|H2|H3|H4|H5|H6"> <!ENTITY % list " UL | OL | DIR | MENU " > <!ENTITY % attrs -- common attributes for elements -- "lang NAME #IMPLIED -- RFC 1766 language tag --">   <!ENTITY % ISOlat1 PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML"> %ISOlat1; <!ENTITY amp CDATA "&" -- ampersand --> <!ENTITY gt CDATA ">" -- greater than --> <!ENTITY lt CDATA "<" -- less than --> <!ENTITY quot CDATA """ -- double quote --> Expires 20 February 1996 [Page 20] Internet Draft HTML internationalization 15 August 1995   <!ENTITY % SDAFORM "SDAFORM CDATA #FIXED" -- one to one mapping --> <!ENTITY % SDARULE "SDARULE CDATA #FIXED" -- context-sensitive mapping --> <!ENTITY % SDAPREF "SDAPREF CDATA #FIXED" -- generated text prefix --> <!ENTITY % SDASUFF "SDASUFF CDATA #FIXED" -- generated text suffix --> <!ENTITY % SDASUSP "SDASUSP NAME #FIXED" -- suspend transform process -->  <![ %HTML.Bidi [ <!ENTITY % HTMLbidi PUBLIC "-//IETF//ENTITIES bidi//EN//HTML"> %HTMLbidi;  <!ENTITY lretag "<BIDI DIR=LTR>" > <!ENTITY rletag "<BIDI DIR=RTL>" > <!ENTITY lrotag "<BIDI FORCE=GAD>" > <!ENTITY rlotag "<BIDI FORCE=DAG>" > <!ENTITY pdftag "</BIDI>" > <!SHORTREF bidi "&#LRE;" lretag Expires 20 February 1996 [Page 21] Internet Draft HTML internationalization 15 August 1995 "&#RLE;" rletag "&#PDF;" pdftag "&#LRO;" lrotag "&#RLO;" rlotag > ]]>  <!ENTITY % loc.values "DATE | TIME | MEASURE | MONEY"> <![ %HTML.Highlighting [ <!ENTITY % font " TT | B | I "> <!ENTITY % phrase "EM | STRONG | CODE | SAMP | KBD | VAR | CITE | Q"> <![ %HTML.Bidi [ <!ENTITY % text "#PCDATA | A | IMG | BR | %phrase | %font | LANG | BIDI | %loc.values"> ]]> <!ENTITY % text "#PCDATA | A | IMG | BR | %phrase | %font | LANG | %loc.values"> <!ELEMENT (%font;|%phrase) - - (%text)*> <!ATTLIST ( TT | CODE | SAMP | KBD | VAR ) %attrs; %SDAFORM; "Lit" > <!ATTLIST ( B | STRONG ) %attrs; %SDAFORM; "B" > <!ATTLIST ( I | EM | CITE ) %attrs; %SDAFORM; "It" >           Expires 20 February 1996 [Page 22] Internet Draft HTML internationalization 15 August 1995 <!ENTITY % pre.content "#PCDATA | A | HR | BR | %font | %phrase | LANG"> ]]> <![ %HTML.Bidi [ <!ENTITY % text "#PCDATA | A | IMG | BR | LANG | BIDI | Q | %loc.values">  <!ELEMENT BIDI - - (%text)+> <!ATTLIST BIDI %attrs; DIR (ltr|rtl) #IMPLIED FORCE (gad|dag) #IMPLIED >  ]]> <!ENTITY % text "#PCDATA | A | IMG | BR | LANG | Q | %loc.values"> <!ELEMENT BR - O EMPTY> <!ATTLIST BR %SDAPREF; "&#RE;" >   <!ELEMENT LANG - - (text)*> <!ATTLIST LANG %attrs; >  <!ATTLIST Q %attrs; %SDAFORM; "It" -- to be verified -- >   <!ELEMENT (%loc.values) - O EMPTY> <!ATTLIST DATE %attrs; Expires 20 February 1996 [Page 23] Internet Draft HTML internationalization 15 August 1995 CALENDAR CDATA #IMPLIED VALUE CDATA #REQUIRED > <!ATTLIST TIME %attrs; ZONE CDATA #IMPLIED VALUE CDATA #REQUIRED > <!ATTLIST MEASURE %attrs; TYPE (weight|count|length|area|volume) #REQUIRED UNIT CDATA #IMPLIED VALUE CDATA #REQUIRED > <!ATTLIST MONEY %attrs; UNIT CDATA #REQUIRED VALUE CDATA #REQUIRED >      <!ENTITY % linkType "NAME"> <!ENTITY % linkExtraAttributes "REL %linkType #IMPLIED REV %linkType #IMPLIED URN CDATA #IMPLIED TITLE CDATA #IMPLIED METHODS NAMES #IMPLIED CHARSET NAME #IMPLIED "> <![ %HTML.Recommended [ <!ENTITY % A.content "(%text)*" -- <H1><a name="xxx">Heading</a></H1> is preferred to <a name="xxx"><H1>Heading</H1></a> --> ]]> <!ENTITY % A.content "(%heading|%text)*"> Expires 20 February 1996 [Page 24] Internet Draft HTML internationalization 15 August 1995 <!ELEMENT A - - %A.content -(A)> <!ATTLIST A %attrs; HREF %URI #IMPLIED NAME CDATA #IMPLIED %linkExtraAttributes; %SDAPREF; "<Anchor: #AttList>" >           <!ELEMENT IMG - O EMPTY> <!ATTLIST IMG %attrs; SRC %URI; #REQUIRED ALT CDATA #IMPLIED ALIGN (top|middle|bottom) #IMPLIED ISMAP (ISMAP) #IMPLIED %SDAPREF; "<Fig><?SDATrans Img: #AttList>#AttVal(Alt)</Fig>" >       <!ELEMENT P - O (%text)*> <!ATTLIST P %attrs; %SDAFORM; "Para" >  Expires 20 February 1996 [Page 25] Internet Draft HTML internationalization 15 August 1995  <!ELEMENT HR - O EMPTY> <!ATTLIST HR %attrs; %SDAPREF; "&#RE;&#RE;" >  <!ELEMENT ( %heading ) - - (%text;)*> <!ATTLIST H1 %attrs; %SDAFORM; "H1" > <!ATTLIST H2 %attrs; %SDAFORM; "H2" > <!ATTLIST H3 %attrs; %SDAFORM; "H3" > <!ATTLIST H4 %attrs; %SDAFORM; "H4" > <!ATTLIST H5 %attrs; %SDAFORM; "H5" > <!ATTLIST H6 %attrs; %SDAFORM; "H6" >        <![ %HTML.Forms [ <!ENTITY % block.forms "BLOCKQUOTE | FORM | ISINDEX"> Expires 20 February 1996 [Page 26] Internet Draft HTML internationalization 15 August 1995 ]]> <!ENTITY % block.forms "BLOCKQUOTE"> <![ %HTML.Deprecated [ <!ENTITY % preformatted "PRE | XMP | LISTING"> ]]> <!ENTITY % preformatted "PRE"> <!ENTITY % block "P | %list | DL | %preformatted | %block.forms"> <!ENTITY % flow "(%text|%block)*"> <!ENTITY % pre.content "#PCDATA | A | HR | BR | LANG"> <!ELEMENT PRE - - (%pre.content)*> <!ATTLIST PRE %attrs; WIDTH NUMBER #implied %SDAFORM; "Lit" >   <![ %HTML.Deprecated [ <!ENTITY % literal "CDATA" -- historical, non-conforming parsing mode where the only markup signal is the end tag in full --> <!ELEMENT (XMP|LISTING) - - %literal> <!ATTLIST XMP %attrs; %SDAFORM; "Lit" %SDAPREF; "Example:&#RE;" > <!ATTLIST LISTING %attrs; %SDAFORM; "Lit" %SDAPREF; "Listing:&#RE;" >  Expires 20 February 1996 [Page 27] Internet Draft HTML internationalization 15 August 1995  <!ELEMENT PLAINTEXT - O %literal>  <!ATTLIST PLAINTEXT %attrs; %SDAFORM; "Lit" > ]]>  <!ELEMENT DL - - (DT | DD)+> <!ATTLIST DL %attrs; COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" %SDAPREF; "Definition List:" > <!ELEMENT DT - O (%text)*> <!ATTLIST DT %attrs; %SDAFORM; "Term" > <!ELEMENT DD - O %flow> <!ATTLIST DD %attrs; %SDAFORM; "LItem" >     <!ELEMENT (OL|UL) - - (LI)+> <!ATTLIST OL %attrs; COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" > <!ATTLIST UL %attrs; COMPACT (COMPACT) #IMPLIED Expires 20 February 1996 [Page 28] Internet Draft HTML internationalization 15 August 1995 %SDAFORM; "List" >     <!ELEMENT (DIR|MENU) - - (LI)+ -(%block)> <!ATTLIST DIR %attrs; COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" %SDAPREF; "<LHead>Directory</LHead>" > <!ATTLIST MENU %attrs; COMPACT (COMPACT) #IMPLIED %SDAFORM; "List" %SDAPREF; "<LHead>Menu</LHead>" >     <!ELEMENT LI - O %flow> <!ATTLIST LI %attrs; %SDAFORM; "LItem" >   <![ %HTML.Recommended [ <!ENTITY % body.content "(%heading|%block|HR|ADDRESS|IMG)*" -- <h1>Heading</h1> <p>Text ... is preferred to <h1>Heading</h1> Text ... --> ]]> <!ENTITY % body.content "(%heading | %text | %block | HR | ADDRESS)*"> Expires 20 February 1996 [Page 29] Internet Draft HTML internationalization 15 August 1995 <!ELEMENT BODY O O %body.content> <!ATTLIST BODY %attrs; >  <!ELEMENT BLOCKQUOTE - - %body.content> <!ATTLIST BLOCKQUOTE %attrs; %SDAFORM; "BQ" >  <!ELEMENT ADDRESS - - (%text|P)*> <!ATTLIST ADDRESS %attrs; %SDAFORM; "Lit" %SDAPREF; "Address:&#RE;" >   <![ %HTML.Forms [ <!ELEMENT FORM - - %body.content -(FORM) +(INPUT|SELECT|TEXTAREA)> <!ATTLIST FORM %attrs; ACTION %URI #IMPLIED METHOD (%HTTP-Method) GET ENCTYPE %Content-Type; "application/x-www-form-urlencoded" ACCEPT-CHARSET CDATA #IMPLIED %SDAPREF; "<Para>Form:</Para>" %SDASUFF; "<Para>Form End.</Para>" >     <!ENTITY % InputType "(TEXT | PASSWORD | CHECKBOX | RADIO | SUBMIT | RESET | IMAGE | HIDDEN | DATE | Expires 20 February 1996 [Page 30] Internet Draft HTML internationalization 15 August 1995 TIME | MEASURE | MONEY | FILE)"> <!ELEMENT INPUT - O EMPTY> <!ATTLIST INPUT %attrs; TYPE %InputType TEXT NAME CDATA #IMPLIED VALUE CDATA #IMPLIED SRC %URI #IMPLIED CHECKED (CHECKED) #IMPLIED SIZE CDATA #IMPLIED MAXLENGTH NUMBER #IMPLIED ALIGN (top|middle|bottom) #IMPLIED ACCEPT CDATA #IMPLIED --list of content types -- %SDAPREF; "Input: " >          <!ELEMENT SELECT - - (OPTION+) -(INPUT|SELECT|TEXTAREA)> <!ATTLIST SELECT %attrs; NAME CDATA #REQUIRED SIZE NUMBER #IMPLIED MULTIPLE (MULTIPLE) #IMPLIED %SDAFORM; "List" %SDAPREF; "<LHead>Select #AttVal(Multiple)</LHead>" >     <!ELEMENT OPTION - O (#PCDATA)*> <!ATTLIST OPTION %attrs; SELECTED (SELECTED) #IMPLIED VALUE CDATA #IMPLIED Expires 20 February 1996 [Page 31] Internet Draft HTML internationalization 15 August 1995 %SDAFORM; "LItem" %SDAPREF; "Option: #AttVal(Value) #AttVal(Selected)" >    <!ELEMENT TEXTAREA - - (#PCDATA)* -(INPUT|SELECT|TEXTAREA)> <!ATTLIST TEXTAREA %attrs; NAME CDATA #REQUIRED ROWS NUMBER #REQUIRED COLS NUMBER #REQUIRED %SDAFORM; "Para" %SDAPREF; "Input Text -- #AttVal(Name): " >     ]]>  <![ %HTML.Recommended [ <!ENTITY % head.extra ""> ]]> <!ENTITY % head.extra "& NEXTID?"> <!ENTITY % head.content "TITLE & ISINDEX? & BASE? %head.extra"> <!ELEMENT HEAD O O (%head.content) +(META|LINK)>  <!ELEMENT TITLE - - (#PCDATA)*> <!ATTLIST TITLE %attrs; %SDAFORM; "Ti" >  <!ELEMENT LINK - O EMPTY> Expires 20 February 1996 [Page 32] Internet Draft HTML internationalization 15 August 1995 <!ATTLIST LINK %attrs; HREF %URI #REQUIRED %linkExtraAttributes; %SDAPREF; "Linked to : #AttVal (TITLE) (URN) (HREF)>" >         <!ELEMENT ISINDEX - O EMPTY> <!ATTLIST ISINDEX %attrs; %SDAPREF; "<Para>[Document is indexed/searchable.]</Para>">  <!ELEMENT BASE - O EMPTY> <!ATTLIST BASE HREF %URI; #REQUIRED >   <!ELEMENT NEXTID - O EMPTY> <!ATTLIST NEXTID N CDATA #REQUIRED >   <!ELEMENT META - O EMPTY> <!ATTLIST META HTTP-EQUIV NAME #IMPLIED NAME NAME #IMPLIED CONTENT CDATA #REQUIRED >     Expires 20 February 1996 [Page 33] Internet Draft HTML internationalization 15 August 1995  <![ %HTML.Deprecated [ <!ENTITY % html.content "HEAD, BODY, PLAINTEXT?"> ]]> <!ENTITY % html.content "HEAD, BODY"> <!ELEMENT HTML O O (%html.content)> <!ENTITY % version.attr "VERSION CDATA #FIXED '%HTML.Version;'"> <!ATTLIST HTML %attrs; %version.attr; %SDAFORM; "Book" >  7.2. SGML Declaration for HTML <!SGML "ISO 8879:1986" -- SGML Declaration for HyperText Markup Language version 2.x (HTML 2.x). -- CHARSET 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 65376 160 CAPACITY SGMLREF TOTALCAP 150000 GRPCAP 150000 ENTCAP 150000 Expires 20 February 1996 [Page 34] Internet Draft HTML internationalization 15 August 1995 SCOPE DOCUMENT SYNTAX SHUNCHAR CONTROLS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 127 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 65536 0 FUNCTION RE 13 RS 10 SPACE 32 TAB SEPCHAR 9 EN-QUAD SEPCHAR 8192 EM-QUAD SEPCHAR 8193 EN-SPACE SEPCHAR 8194 EM-SPACE SEPCHAR 8195 T-P-E-SP SEPCHAR 8196 F-P-E-SP SEPCHAR 8197 S-P-E-SP SEPCHAR 8198 FIG-SP SEPCHAR 8199 PUNC-SP SEPCHAR 8200 THIN-SP SEPCHAR 8201 HAIR-SP SEPCHAR 8202 Z-W-SP SEPCHAR 8203 IDEO-SP SEPCHAR 12288 LRE FUNCHAR 8234 -- LEFT-TO-RIGHT EMBEDDING -- RLE FUNCHAR 8235 -- RIGHT-TO-LEFT EMBEDDING -- PDF FUNCHAR 8236 -- POP DIRECTIONAL FORMATTING -- LRO FUNCHAR 8237 -- LEFT-TO-RIGHT OVERRIDE -- RLO FUNCHAR 8238 -- RIGHT-TO-LEFT OVERRIDE -- NAMING LCNMSTRT "" UCNMSTRT "" LCNMCHAR ".-" UCNMCHAR ".-" NAMECASE GENERAL YES ENTITY NO DELIM GENERAL SGMLREF SHORTREF SGMLREF "‪" -- LEFT-TO-RIGHT EMBEDDING -- "‫" -- RIGHT-TO-LEFT EMBEDDING -- "‬" -- POP DIRECTIONAL FORMATTING -- "‭" -- LEFT-TO-RIGHT OVERRIDE -- "‮" -- RIGHT-TO-LEFT OVERRIDE -- NAMES SGMLREF QUANTITY SGMLREF ATTSPLEN 2100 Expires 20 February 1996 [Page 35] Internet Draft HTML internationalization 15 August 1995 LITLEN 1024 NAMELEN 72 -- somewhat arbitrary; taken from internet line length conventions -- PILEN 1024 TAGLVL 100 TAGLEN 2100 GRPGTCNT 150 GRPCNT 64 FEATURES MINIMIZE DATATAG NO OMITTAG YES RANK NO SHORTTAG YES LINK SIMPLE NO IMPLICIT NO EXPLICIT NO OTHER CONCUR NO SUBDOC NO FORMAL YES APPINFO "SDA" -- conforming SGML Document Access application -- > 7.3. Entity sets 7.3.1. ISO Latin 1 Character 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, and description. This list is derived from ISO Standard 8879:1986//ENTITIES Added Latin 1//EN. HTML includes the entire entity set, and adds enti- ties for all missing characters in the right part of ISO-8859-1.   Expires 20 February 1996 [Page 36] Internet Draft HTML internationalization 15 August 1995 <!ENTITY nbsp CDATA " " -- no-break space --> <!ENTITY iexcl CDATA "¡" -- inverted exclamation mark --> <!ENTITY cent CDATA "¢" -- cent sign --> <!ENTITY pound CDATA "£" -- pound sterling sign --> <!ENTITY curren CDATA "¤" -- general currency sign --> <!ENTITY yen CDATA "¥" -- yen sign --> <!ENTITY brvbar CDATA "¦" -- broken (vertical) bar --> <!ENTITY sect CDATA "§" -- section sign --> <!ENTITY uml CDATA "¨" -- umlaut (dieresis) --> <!ENTITY copy CDATA "©" -- copyright sign --> <!ENTITY ordf CDATA "ª" -- ordinal indicator, feminine --> <!ENTITY laquo CDATA "«" -- angle quotation mark, left --> <!ENTITY not CDATA "¬" -- not sign --> <!ENTITY shy CDATA "" -- soft hyphen --> <!ENTITY reg CDATA "®" -- registered sign --> <!ENTITY macr CDATA "¯" -- macron --> <!ENTITY deg CDATA "°" -- degree sign --> <!ENTITY plusmn CDATA "±" -- plus-or-minus sign --> <!ENTITY sup2 CDATA "²" -- superscript two --> <!ENTITY sup3 CDATA "³" -- superscript three --> <!ENTITY acute CDATA "´" -- acute accent --> <!ENTITY micro CDATA "µ" -- micro sign --> <!ENTITY para CDATA "¶" -- pilcrow (paragraph sign) --> <!ENTITY middot CDATA "·" -- middle dot --> <!ENTITY cedil CDATA "¸" -- cedilla --> <!ENTITY sup1 CDATA "¹" -- superscript one --> <!ENTITY ordm CDATA "º" -- ordinal indicator, masculine --> <!ENTITY raquo CDATA "»" -- angle quotation mark, right --> <!ENTITY frac14 CDATA "¼" -- fraction one-quarter --> <!ENTITY frac12 CDATA "½" -- fraction one-half --> <!ENTITY frac34 CDATA "¾" -- fraction three-quarters --> <!ENTITY iquest CDATA "¿" -- inverted question mark --> <!ENTITY Agrave CDATA "À" -- capital A, grave accent --> <!ENTITY Aacute CDATA "Á" -- capital A, acute accent --> <!ENTITY Acirc CDATA "Â" -- capital A, circumflex accent --> <!ENTITY Atilde CDATA "Ã" -- capital A, tilde --> <!ENTITY Auml CDATA "Ä" -- capital A, dieresis or umlaut mark --> <!ENTITY Aring CDATA "Å" -- capital A, ring --> <!ENTITY AElig CDATA "Æ" -- capital AE diphthong (ligature) --> <!ENTITY Ccedil CDATA "Ç" -- capital C, cedilla --> <!ENTITY Egrave CDATA "È" -- capital E, grave accent --> <!ENTITY Eacute CDATA "É" -- capital E, acute accent --> <!ENTITY Ecirc CDATA "Ê" -- capital E, circumflex accent --> <!ENTITY Euml CDATA "Ë" -- capital E, dieresis or umlaut mark --> <!ENTITY Igrave CDATA "Ì" -- capital I, grave accent --> <!ENTITY Iacute CDATA "Í" -- capital I, acute accent --> <!ENTITY Icirc CDATA "Î" -- capital I, circumflex accent --> <!ENTITY Iuml CDATA "Ï" -- capital I, dieresis or umlaut mark --> Expires 20 February 1996 [Page 37] Internet Draft HTML internationalization 15 August 1995 <!ENTITY ETH CDATA "Ð" -- capital Eth, Icelandic --> <!ENTITY Ntilde CDATA "Ñ" -- capital N, tilde --> <!ENTITY Ograve CDATA "Ò" -- capital O, grave accent --> <!ENTITY Oacute CDATA "Ó" -- capital O, acute accent --> <!ENTITY Ocirc CDATA "Ô" -- capital O, circumflex accent --> <!ENTITY Otilde CDATA "Õ" -- capital O, tilde --> <!ENTITY Ouml CDATA "Ö" -- capital O, dieresis or umlaut mark --> <!ENTITY times CDATA "×" -- multiply sign --> <!ENTITY Oslash CDATA "Ø" -- capital O, slash --> <!ENTITY Ugrave CDATA "Ù" -- capital U, grave accent --> <!ENTITY Uacute CDATA "Ú" -- capital U, acute accent --> <!ENTITY Ucirc CDATA "Û" -- capital U, circumflex accent --> <!ENTITY Uuml CDATA "Ü" -- capital U, dieresis or umlaut mark --> <!ENTITY Yacute CDATA "Ý" -- capital Y, acute accent --> <!ENTITY THORN CDATA "Þ" -- capital Thorn, Icelandic --> <!ENTITY szlig CDATA "ß" -- small sharp s, German (sz ligature) --> <!ENTITY agrave CDATA "à" -- small a, grave accent --> <!ENTITY aacute CDATA "á" -- small a, acute accent --> <!ENTITY acirc CDATA "â" -- small a, circumflex accent --> <!ENTITY atilde CDATA "ã" -- small a, tilde --> <!ENTITY auml CDATA "ä" -- small a, dieresis or umlaut mark --> <!ENTITY aring CDATA "å" -- small a, ring --> <!ENTITY aelig CDATA "æ" -- small ae diphthong (ligature) --> <!ENTITY ccedil CDATA "ç" -- small c, cedilla --> <!ENTITY egrave CDATA "è" -- small e, grave accent --> <!ENTITY eacute CDATA "é" -- small e, acute accent --> <!ENTITY ecirc CDATA "ê" -- small e, circumflex accent --> <!ENTITY euml CDATA "ë" -- small e, dieresis or umlaut mark --> <!ENTITY igrave CDATA "ì" -- small i, grave accent --> <!ENTITY iacute CDATA "í" -- small i, acute accent --> <!ENTITY icirc CDATA "î" -- small i, circumflex accent --> <!ENTITY iuml CDATA "ï" -- small i, dieresis or umlaut mark --> <!ENTITY eth CDATA "ð" -- small eth, Icelandic --> <!ENTITY ntilde CDATA "ñ" -- small n, tilde --> <!ENTITY ograve CDATA "ò" -- small o, grave accent --> <!ENTITY oacute CDATA "ó" -- small o, acute accent --> <!ENTITY ocirc CDATA "ô" -- small o, circumflex accent --> <!ENTITY otilde CDATA "õ" -- small o, tilde --> <!ENTITY ouml CDATA "ö" -- small o, dieresis or umlaut mark --> <!ENTITY divide CDATA "÷" -- divide sign --> <!ENTITY oslash CDATA "ø" -- small o, slash --> <!ENTITY ugrave CDATA "ù" -- small u, grave accent --> <!ENTITY uacute CDATA "ú" -- small u, acute accent --> <!ENTITY ucirc CDATA "û" -- small u, circumflex accent --> <!ENTITY uuml CDATA "ü" -- small u, dieresis or umlaut mark --> <!ENTITY yacute CDATA "ý" -- small y, acute accent --> <!ENTITY thorn CDATA "þ" -- small thorn, Icelandic --> <!ENTITY yuml CDATA "ÿ" -- small y, dieresis or umlaut mark --> Expires 20 February 1996 [Page 38] Internet Draft HTML internationalization 15 August 1995 7.3.2. BIDI Entity Set The following entity set is sufficient to support the full Unicode bidirectionnal algorithm.  <!ENTITY zwnj SDATA "‌"--=zero width non-joiner--> <!ENTITY zwj SDATA "‍"--=zero width joiner--> <!ENTITY lrm SDATA "‎"--=left-to-right mark--> <!ENTITY rlm SDATA "‏"--=right-to-left mark--> <!ENTITY lre SDATA "‪"--=left-to-right embedding--> <!ENTITY rle SDATA "‫"--=right-to-left embedding--> <!ENTITY pdf SDATA "‬"--=pop directional formatting--> <!ENTITY lro SDATA "‭"--=left-to-right override--> <!ENTITY rlo SDATA "‮"--=right-to-left override--> 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. <http://www.sgmlopen.org/sgml/docs/ercs/ercs- home.html> [FILE-UPLOAD] E. Nebel and L. Masinter, "Form-based File Upload in HTML", Work in progress (draft-ietf-html- fileupload-02.txt), Xerox Corporation, April 1995. [GOLD90] C. F. Goldfarb, "The SGML Handbook", Y. Rubinsky, Ed., Oxford University Press, 1990. [HTML-2] T. Berners-Lee and D. Connolly, "Hypertext Markup Lan- guage - 2.0", Work in progress (draft-ietf-html- spec-02.txt), MIT/W3C, May 1995. [HTTP] T. Berners-Lee, R. T. Fielding, and H. Frystyk Nielsen, "Hypertext Transfer Protocol - HTTP/1.0", Work in progress (draft-ietf-http-v10-spec-00.ps), MIT, UC Irvine, CERN, March 1995. [ISO-639] ISO 639:1988. Codes pour la reprΘsentation des noms de Expires 20 February 1996 [Page 39] Internet Draft HTML internationalization 15 August 1995 langue. Technical content in <http://www.sil.org/sgml/iso639a.html> [ISO-CD-639-2] ISO CD 639-2:1992. Technical content in <http://www.sil.org/sgml/iso639-2a.html> [ISO-1000] ISO 1000:1992. UnitΘs SI et recommandations pour l'emploi de leurs multiples et de certaines autres unitΘs. [ISO-3166] ISO 3166:1993. Codes pour la reprΘsentation des noms de pays. [ISO-4217] ISO 4217:1990. Codes pour la reprΘsentation des mon- naies et types des fonds. [ISO-8601] ISO 8601:1988. ╔lΘments de donnΘes et formats d'Θchange -- ╔change d'information -- ReprΘsentation 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, <http://www.ebt.com/docs/multling.html> [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. Expires 20 February 1996 [Page 40] Internet Draft HTML internationalization 15 August 1995 [RFC1738] T. Berners-Lee, L. Masinter, and M. McCahill, "Uniform 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. [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. <http://etext.virgina.edu/TEI.html> [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. [VANH90] E. van Hervijnen, "Practical SGML", Kluwer Academicq Publishers Group, Norwell and Dordrecht, 1990. Authors' Addresses Franτois Yergeau Alis Technologies 3410, rue Griffith MontrΘal QC H4T 1A7 Canada Tel: +1 (514) 738-9171 Fax: +1 (514) 342-0318 EMail: yergeau@alis.ca Gavin Thomas Nicol Electronic Book Technologies, Japan 1-29-9 Tsurumaki, Setagaya-ku, Tokyo Japan Tel + Fax: +81-3-3706-7351 EMail: gtn@ebt.com, gtn@twics.co.jp Expires 20 February 1996 [Page 41] Internet Draft HTML internationalization 15 August 1995 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 20 February 1996 [Page 42]