2004/id/draft-ietf-html-i18n-00.txt

    
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
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   To learn the current status of any Internet-Draft, please check the
   1id-abstracts.txt listing contained in the Internet-Drafts Shadow
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   (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


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   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].


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   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


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      (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.


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   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.


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   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


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   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, &#1048; 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.


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   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


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   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


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   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].


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   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}?


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   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-->


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   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         &#8204;
   0x200D ZERO WIDTH JOINER             &#8205;
   0x200E LEFT-TO-RIGHT MARK            &#8206;
   0x200F RIGHT-TO-LEFT MARK            &#8207;
   0x202A LEFT-TO-RIGHT EMBEDDING       &#8234;
   0x202B RIGHT-TO-LEFT EMBEDDING       &#8235;
   0x202C POP DIRECTIONAL FORMATTING    &#8236;
   0x202D LEFT-TO-RIGHT OVERRIDE        &#8237;
   0x202E RIGHT-TO-LEFT OVERRIDE        &#8238;

   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:


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        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


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   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


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   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.


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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


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   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

   <!--    html-2.x.dtd

           Document Type Definition for the HyperText Markup Language,
           version 2.x (HTML DTD)

           Authors: Daniel W. Connolly <connolly@w3.org>
                    Franois Yergeau <yergeau@alis.com>
   -->

   <!ENTITY % HTML.Version
           "-//IETF//DTD HTML 2.x//EN"

           -- Typical usage:


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               <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.x//EN">
               <html>
               ...
               </html>
           --
           >


   <!--============ Feature Test Entities ========================-->

   <!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


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           -->

   <!--============== Imported Names ==============================-->

   <!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.

           -->


   <!--========= DTD "Macros" =====================-->

   <!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 --">
            <!--or CDATA?-->

   <!--======= Character mnemonic entities =================-->

   <!ENTITY % ISOlat1 PUBLIC
     "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
   %ISOlat1;

   <!ENTITY amp CDATA "&#38;"     -- ampersand          -->
   <!ENTITY gt CDATA "&#62;"      -- greater than       -->
   <!ENTITY lt CDATA "&#60;"      -- less than          -->
   <!ENTITY quot CDATA "&#34;"    -- double quote       -->


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   <!--========= SGML Document Access (SDA) Parameter Entities =====-->

   <!-- HTML 2.0 contains SGML Document Access (SDA) fixed attributes
   in support of easy transformation to the International Committee
   for Accessible Document Design (ICADD) DTD
            "-//EC-USA-CDA/ICADD//DTD ICADD22//EN".
   ICADD applications are designed to support usable access to
   structured information by print-impaired individuals through
   Braille, large print and voice synthesis.  For more information on
   SDA & ICADD:
           - ISO 12083:1993, Annex A.8, Facilities for Braille,
             large print and computer voice
           - ICADD ListServ
             <ICADD%ASUACAD.BITNET@ARIZVM1.ccit.arizona.edu>
           - Usenet news group bit.listserv.easi
           - Recording for the Blind, +1 800 221 4792
   -->

   <!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 -->


   <!--========= Entities for bidirectionnal text (BIDI) =========-->

   <![ %HTML.Bidi [

   <!ENTITY % HTMLbidi PUBLIC
     "-//IETF//ENTITIES bidi//EN//HTML">
   %HTMLbidi;

   <!-- The following, together with the BIDI element, allow dealing
        with text containing BIDI controls in the context of marked
        up text. -->
   <!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


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           "&#RLE;" rletag
           "&#PDF;" pdftag
           "&#LRO;" lrotag
           "&#RLO;" rlotag
           >

   ]]>

   <!--========== Text Markup =====================-->

   <!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"
           >

   <!-- <TT>       Typewriter text                         -->
   <!-- <B>        Bold text                               -->
   <!-- <I>        Italic text                             -->
   <!-- <EM>       Emphasized phrase                       -->
   <!-- <STRONG>   Strong emphasis                         -->
   <!-- <CODE>     Source code phrase                      -->
   <!-- <SAMP>     Sample text or characters               -->
   <!-- <KBD>      Keyboard phrase, e.g. user input        -->
   <!-- <VAR>      Variable phrase or substituable         -->
   <!-- <CITE>     Name or title of cited work             -->


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   <!ENTITY % pre.content "#PCDATA | A | HR | BR | %font | %phrase | LANG">

   ]]>

   <![ %HTML.Bidi [

   <!ENTITY % text "#PCDATA | A | IMG | BR | LANG | BIDI | Q | %loc.values">

   <!-- Should the BIDI element have an SDAFORM attr.?  Which? -->
   <!ELEMENT BIDI - - (%text)+>
   <!ATTLIST BIDI
           %attrs;
           DIR   (ltr|rtl) #IMPLIED
           FORCE (gad|dag) #IMPLIED
           >

   <!-- <BIDI>     Control bidirectionnal text             -->

   ]]>

   <!ENTITY % text "#PCDATA | A | IMG | BR | LANG | Q | %loc.values">

   <!ELEMENT BR    - O EMPTY>
   <!ATTLIST BR
           %SDAPREF; "&#RE;"
           >

   <!-- <BR>       Line break      -->

   <!-- Should the LANG element have an SDAFORM attr.?  Which? -->
   <!ELEMENT LANG - - (text)*>
   <!ATTLIST LANG
           %attrs;
           >

   <!-- <LANG>     Container for language attribute        -->

   <!ATTLIST Q
           %attrs;
           %SDAFORM; "It"  -- to be verified --
           >
   <!-- <Q>        Short quotation                         -->

   <!--========= Date, time, measures and monetary amounts ===========-->

   <!ELEMENT (%loc.values) - O EMPTY>
   <!ATTLIST DATE
           %attrs;


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           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
           >

   <!-- DATE       A date value                          -->
   <!-- TIME       A time value                          -->
   <!-- MEASURE    A measurement (length, weight, etc)   -->
   <!-- MONEY      A monetary amount                     -->

   <!--========= Link Markup ======================-->

   <!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)*">


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   <!ELEMENT A     - - %A.content -(A)>
   <!ATTLIST A
           %attrs;
           HREF %URI #IMPLIED
           NAME CDATA #IMPLIED
           %linkExtraAttributes;
           %SDAPREF; "<Anchor: #AttList>"
           >
   <!-- <A>                Anchor; source/destination of link      -->
   <!-- <A NAME="...">     Name of this anchor                     -->
   <!-- <A HREF="...">     Address of link destination             -->
   <!-- <A URN="...">      Permanent address of destination        -->
   <!-- <A REL=...>        Relationship to destination             -->
   <!-- <A REV=...>        Relationship of destination to this     -->
   <!-- <A TITLE="...">    Title of destination (advisory)         -->
   <!-- <A CHARSET="...">  Charset of destination (advisory)               -->
   <!-- <A METHODS="...">  Operations on destination (advisory)    -->


   <!--========== Images ==========================-->

   <!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>"
           >

   <!-- <IMG>              Image; icon, glyph or illustration      -->
   <!-- <IMG SRC="...">    Address of image object                 -->
   <!-- <IMG ALT="...">    Textual alternative                     -->
   <!-- <IMG ALIGN=...>    Position relative to text               -->
   <!-- <IMG ISMAP>        Each pixel can be a link                -->

   <!--========== Paragraphs=======================-->

   <!ELEMENT P     - O (%text)*>
   <!ATTLIST P
           %attrs;
           %SDAFORM; "Para"
           >

   <!-- <P>        Paragraph       -->


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   <!--========== Headings, Titles, Sections ===============-->

   <!ELEMENT HR    - O EMPTY>
   <!ATTLIST HR
           %attrs;
           %SDAPREF; "&#RE;&#RE;"
           >

   <!-- <HR>       Horizontal rule -->

   <!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"
           >

   <!-- <H1>       Heading, level 1 -->
   <!-- <H2>       Heading, level 2 -->
   <!-- <H3>       Heading, level 3 -->
   <!-- <H4>       Heading, level 4 -->
   <!-- <H5>       Heading, level 5 -->
   <!-- <H6>       Heading, level 6 -->


   <!--========== Text Flows ======================-->

   <![ %HTML.Forms [
           <!ENTITY % block.forms "BLOCKQUOTE | FORM | ISINDEX">


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   ]]>

   <!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"
           >

   <!-- <PRE>              Preformatted text               -->
   <!-- <PRE WIDTH=...>    Maximum characters per line     -->

   <![ %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;"
           >

   <!-- <XMP>              Example section         -->


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   <!-- <LISTING>          Computer listing        -->

   <!ELEMENT PLAINTEXT - O %literal>
   <!-- <PLAINTEXT>        Plain text passage      -->

   <!ATTLIST PLAINTEXT
           %attrs;
           %SDAFORM; "Lit"
           >
   ]]>


   <!--========== Lists ==================-->

   <!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"
           >

   <!-- <DL>               Definition list, or glossary    -->
   <!-- <DL COMPACT>       Compact style list              -->
   <!-- <DT>               Term in definition list         -->
   <!-- <DD>               Definition of term              -->

   <!ELEMENT (OL|UL) - -  (LI)+>
   <!ATTLIST OL
           %attrs;
           COMPACT (COMPACT) #IMPLIED
           %SDAFORM; "List"
           >
   <!ATTLIST UL
           %attrs;
           COMPACT (COMPACT) #IMPLIED


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           %SDAFORM; "List"
           >
   <!-- <UL>               Unordered list                  -->
   <!-- <UL COMPACT>       Compact list style              -->
   <!-- <OL>               Ordered, or numbered list       -->
   <!-- <OL COMPACT>       Compact list style              -->


   <!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>"
           >

   <!-- <DIR>              Directory list                  -->
   <!-- <DIR COMPACT>      Compact list style              -->
   <!-- <MENU>             Menu list                       -->
   <!-- <MENU COMPACT>     Compact list style              -->

   <!ELEMENT LI    - O %flow>
   <!ATTLIST LI
           %attrs;
           %SDAFORM; "LItem"
           >

   <!-- <LI>               List item                       -->

   <!--========== Document Body ===================-->

   <![ %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)*">


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   <!ELEMENT BODY O O  %body.content>
   <!ATTLIST BODY
           %attrs;
           >

   <!-- <BODY>     Document body   -->

   <!ELEMENT BLOCKQUOTE - - %body.content>
   <!ATTLIST BLOCKQUOTE
           %attrs;
           %SDAFORM; "BQ"
           >

   <!-- <BLOCKQUOTE>       Quoted passage  -->

   <!ELEMENT ADDRESS - - (%text|P)*>
   <!ATTLIST  ADDRESS
           %attrs;
           %SDAFORM; "Lit"
           %SDAPREF; "Address:&#RE;"
           >

   <!-- <ADDRESS>  Address, signature, or byline   -->


   <!--======= Forms ====================-->

   <![ %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>"
           >

   <!-- <FORM>                     Fill-out or data-entry form     -->
   <!-- <FORM ACTION="...">        Address for completed form      -->
   <!-- <FORM METHOD=...>          Method of submitting form       -->
   <!-- <FORM ENCTYPE="...">       Representation of form data     -->

   <!ENTITY % InputType "(TEXT | PASSWORD | CHECKBOX |
                          RADIO | SUBMIT | RESET |
                          IMAGE | HIDDEN | DATE |


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                          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: "
           >

   <!-- <INPUT>                    Form input datum                -->
   <!-- <INPUT TYPE=...>           Type of input interaction       -->
   <!-- <INPUT NAME=...>           Name of form datum              -->
   <!-- <INPUT VALUE="...">        Default/initial/selected value  -->
   <!-- <INPUT SRC="...">          Address of image                -->
   <!-- <INPUT CHECKED>            Initial state is "on"           -->
   <!-- <INPUT SIZE=...>           Field size hint                 -->
   <!-- <INPUT MAXLENGTH=...>      Data length maximum             -->
   <!-- <INPUT ALIGN=...>          Image alignment                 -->

   <!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>"
           >

   <!-- <SELECT>                   Selection of option(s)          -->
   <!-- <SELECT NAME=...>          Name of form datum              -->
   <!-- <SELECT SIZE=...>          Options displayed at a time     -->
   <!-- <SELECT MULTIPLE>          Multiple selections allowed     -->

   <!ELEMENT OPTION - O (#PCDATA)*>
   <!ATTLIST OPTION
           %attrs;
           SELECTED (SELECTED) #IMPLIED
           VALUE CDATA #IMPLIED


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           %SDAFORM; "LItem"
           %SDAPREF;
           "Option: #AttVal(Value) #AttVal(Selected)"
           >

   <!-- <OPTION>                   A selection option              -->
   <!-- <OPTION SELECTED>          Initial state                   -->
   <!-- <OPTION VALUE="...">       Form datum value for this option-->

   <!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): "
           >

   <!-- <TEXTAREA>            An area for text input -->
   <!-- <TEXTAREA NAME=...>   Name of form datum     -->
   <!-- <TEXTAREA ROWS=...>   Height of area         -->
   <!-- <TEXTAREA COLS=...>   Width of area          -->

   ]]>


   <!--======= Document Head ======================-->

   <![ %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)>

   <!-- <HEAD>     Document head   -->

   <!ELEMENT TITLE - -  (#PCDATA)*>
   <!ATTLIST TITLE
           %attrs;
           %SDAFORM; "Ti"    >

   <!-- <TITLE>    Title of document -->

   <!ELEMENT LINK - O EMPTY>


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   <!ATTLIST LINK
           %attrs;
           HREF %URI #REQUIRED
           %linkExtraAttributes;
           %SDAPREF; "Linked to : #AttVal (TITLE) (URN) (HREF)>"    >

   <!-- <LINK>             Link from this document                 -->
   <!-- <LINK HREF="...">  Address of link destination             -->
   <!-- <LINK URN="...">   Lasting name of destination             -->
   <!-- <LINK REL=...>     Relationship to destination             -->
   <!-- <LINK REV=...>     Relationship of destination to this     -->
   <!-- <LINK TITLE="..."> Title of destination (advisory)         -->
   <!-- <LINK CHARSET="...">       Charset of destination (advisory)               -->
   <!-- <LINK METHODS="..."> Operations allowed (advisory)         -->

   <!ELEMENT ISINDEX - O EMPTY>
   <!ATTLIST ISINDEX
           %attrs;
           %SDAPREF;
      "<Para>[Document is indexed/searchable.]</Para>">

   <!-- <ISINDEX>          Document is a searchable index          -->

   <!ELEMENT BASE - O EMPTY>
   <!ATTLIST BASE
           HREF %URI; #REQUIRED     >

   <!-- <BASE>             Base context document                   -->
   <!-- <BASE HREF="...">  Address for this document               -->

   <!ELEMENT NEXTID - O EMPTY>
   <!ATTLIST NEXTID
           N CDATA #REQUIRED     >

   <!-- <NEXTID>           Next ID to use for link name            -->
   <!-- <NEXTID N=...>     Next ID to use for link name            -->

   <!ELEMENT META - O EMPTY>
   <!ATTLIST META
           HTTP-EQUIV  NAME    #IMPLIED
           NAME        NAME    #IMPLIED
           CONTENT     CDATA   #REQUIRED
           >

   <!-- <META>                     Generic Metainformation         -->
   <!-- <META HTTP-EQUIV=...>      HTTP response header name       -->
   <!-- <META NAME=...>            Metainformation name            -->
   <!-- <META CONTENT="...">       Associated information          -->


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   <!--======= Document Structure =================-->

   <![ %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"
           >

   <!-- <HTML>                     HTML Document                   -->


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


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   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
                           "&#8234;"      -- LEFT-TO-RIGHT EMBEDDING    --
                           "&#8235;"      -- RIGHT-TO-LEFT EMBEDDING    --
                           "&#8236;"      -- POP DIRECTIONAL FORMATTING --
                           "&#8237;"      -- LEFT-TO-RIGHT OVERRIDE     --
                           "&#8238;"      -- RIGHT-TO-LEFT OVERRIDE     --
            NAMES    SGMLREF
            QUANTITY SGMLREF
                     ATTSPLEN 2100


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                     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.

 <!-- (C) International Organization for Standardization 1986
      Permission to copy in any form is granted for use with
      conforming SGML systems and applications as defined in
      ISO 8879, provided this notice is included in all copies.
   -->
 <!-- Character entity set. Typical invocation:
      <!ENTITY % ISOlat1 PUBLIC
        "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
      %ISOlat1;
   -->


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 <!ENTITY nbsp   CDATA "&#160;" -- no-break space -->
 <!ENTITY iexcl  CDATA "&#161;" -- inverted exclamation mark -->
 <!ENTITY cent   CDATA "&#162;" -- cent sign -->
 <!ENTITY pound  CDATA "&#163;" -- pound sterling sign -->
 <!ENTITY curren CDATA "&#164;" -- general currency sign -->
 <!ENTITY yen    CDATA "&#165;" -- yen sign -->
 <!ENTITY brvbar CDATA "&#166;" -- broken (vertical) bar -->
 <!ENTITY sect   CDATA "&#167;" -- section sign -->
 <!ENTITY uml    CDATA "&#168;" -- umlaut (dieresis) -->
 <!ENTITY copy   CDATA "&#169;" -- copyright sign -->
 <!ENTITY ordf   CDATA "&#170;" -- ordinal indicator, feminine -->
 <!ENTITY laquo  CDATA "&#171;" -- angle quotation mark, left -->
 <!ENTITY not    CDATA "&#172;" -- not sign -->
 <!ENTITY shy    CDATA "&#173;" -- soft hyphen -->
 <!ENTITY reg    CDATA "&#174;" -- registered sign -->
 <!ENTITY macr   CDATA "&#175;" -- macron -->
 <!ENTITY deg    CDATA "&#176;" -- degree sign -->
 <!ENTITY plusmn CDATA "&#177;" -- plus-or-minus sign -->
 <!ENTITY sup2   CDATA "&#178;" -- superscript two -->
 <!ENTITY sup3   CDATA "&#179;" -- superscript three -->
 <!ENTITY acute  CDATA "&#180;" -- acute accent -->
 <!ENTITY micro  CDATA "&#181;" -- micro sign -->
 <!ENTITY para   CDATA "&#182;" -- pilcrow (paragraph sign) -->
 <!ENTITY middot CDATA "&#183;" -- middle dot -->
 <!ENTITY cedil  CDATA "&#184;" -- cedilla -->
 <!ENTITY sup1   CDATA "&#185;" -- superscript one -->
 <!ENTITY ordm   CDATA "&#186;" -- ordinal indicator, masculine -->
 <!ENTITY raquo  CDATA "&#187;" -- angle quotation mark, right -->
 <!ENTITY frac14 CDATA "&#188;" -- fraction one-quarter -->
 <!ENTITY frac12 CDATA "&#189;" -- fraction one-half -->
 <!ENTITY frac34 CDATA "&#190;" -- fraction three-quarters -->
 <!ENTITY iquest CDATA "&#191;" -- inverted question mark -->
 <!ENTITY Agrave CDATA "&#192;" -- capital A, grave accent -->
 <!ENTITY Aacute CDATA "&#193;" -- capital A, acute accent -->
 <!ENTITY Acirc  CDATA "&#194;" -- capital A, circumflex accent -->
 <!ENTITY Atilde CDATA "&#195;" -- capital A, tilde -->
 <!ENTITY Auml   CDATA "&#196;" -- capital A, dieresis or umlaut mark -->
 <!ENTITY Aring  CDATA "&#197;" -- capital A, ring -->
 <!ENTITY AElig  CDATA "&#198;" -- capital AE diphthong (ligature) -->
 <!ENTITY Ccedil CDATA "&#199;" -- capital C, cedilla -->
 <!ENTITY Egrave CDATA "&#200;" -- capital E, grave accent -->
 <!ENTITY Eacute CDATA "&#201;" -- capital E, acute accent -->
 <!ENTITY Ecirc  CDATA "&#202;" -- capital E, circumflex accent -->
 <!ENTITY Euml   CDATA "&#203;" -- capital E, dieresis or umlaut mark -->
 <!ENTITY Igrave CDATA "&#204;" -- capital I, grave accent -->
 <!ENTITY Iacute CDATA "&#205;" -- capital I, acute accent -->
 <!ENTITY Icirc  CDATA "&#206;" -- capital I, circumflex accent -->
 <!ENTITY Iuml   CDATA "&#207;" -- capital I, dieresis or umlaut mark -->


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 <!ENTITY ETH    CDATA "&#208;" -- capital Eth, Icelandic -->
 <!ENTITY Ntilde CDATA "&#209;" -- capital N, tilde -->
 <!ENTITY Ograve CDATA "&#210;" -- capital O, grave accent -->
 <!ENTITY Oacute CDATA "&#211;" -- capital O, acute accent -->
 <!ENTITY Ocirc  CDATA "&#212;" -- capital O, circumflex accent -->
 <!ENTITY Otilde CDATA "&#213;" -- capital O, tilde -->
 <!ENTITY Ouml   CDATA "&#214;" -- capital O, dieresis or umlaut mark -->
 <!ENTITY times  CDATA "&#215;" -- multiply sign -->
 <!ENTITY Oslash CDATA "&#216;" -- capital O, slash -->
 <!ENTITY Ugrave CDATA "&#217;" -- capital U, grave accent -->
 <!ENTITY Uacute CDATA "&#218;" -- capital U, acute accent -->
 <!ENTITY Ucirc  CDATA "&#219;" -- capital U, circumflex accent -->
 <!ENTITY Uuml   CDATA "&#220;" -- capital U, dieresis or umlaut mark -->
 <!ENTITY Yacute CDATA "&#221;" -- capital Y, acute accent -->
 <!ENTITY THORN  CDATA "&#222;" -- capital Thorn, Icelandic -->
 <!ENTITY szlig  CDATA "&#223;" -- small sharp s, German (sz ligature) -->
 <!ENTITY agrave CDATA "&#224;" -- small a, grave accent -->
 <!ENTITY aacute CDATA "&#225;" -- small a, acute accent -->
 <!ENTITY acirc  CDATA "&#226;" -- small a, circumflex accent -->
 <!ENTITY atilde CDATA "&#227;" -- small a, tilde -->
 <!ENTITY auml   CDATA "&#228;" -- small a, dieresis or umlaut mark -->
 <!ENTITY aring  CDATA "&#229;" -- small a, ring -->
 <!ENTITY aelig  CDATA "&#230;" -- small ae diphthong (ligature) -->
 <!ENTITY ccedil CDATA "&#231;" -- small c, cedilla -->
 <!ENTITY egrave CDATA "&#232;" -- small e, grave accent -->
 <!ENTITY eacute CDATA "&#233;" -- small e, acute accent -->
 <!ENTITY ecirc  CDATA "&#234;" -- small e, circumflex accent -->
 <!ENTITY euml   CDATA "&#235;" -- small e, dieresis or umlaut mark -->
 <!ENTITY igrave CDATA "&#236;" -- small i, grave accent -->
 <!ENTITY iacute CDATA "&#237;" -- small i, acute accent -->
 <!ENTITY icirc  CDATA "&#238;" -- small i, circumflex accent -->
 <!ENTITY iuml   CDATA "&#239;" -- small i, dieresis or umlaut mark -->
 <!ENTITY eth    CDATA "&#240;" -- small eth, Icelandic -->
 <!ENTITY ntilde CDATA "&#241;" -- small n, tilde -->
 <!ENTITY ograve CDATA "&#242;" -- small o, grave accent -->
 <!ENTITY oacute CDATA "&#243;" -- small o, acute accent -->
 <!ENTITY ocirc  CDATA "&#244;" -- small o, circumflex accent -->
 <!ENTITY otilde CDATA "&#245;" -- small o, tilde -->
 <!ENTITY ouml   CDATA "&#246;" -- small o, dieresis or umlaut mark -->
 <!ENTITY divide CDATA "&#247;" -- divide sign -->
 <!ENTITY oslash CDATA "&#248;" -- small o, slash -->
 <!ENTITY ugrave CDATA "&#249;" -- small u, grave accent -->
 <!ENTITY uacute CDATA "&#250;" -- small u, acute accent -->
 <!ENTITY ucirc  CDATA "&#251;" -- small u, circumflex accent -->
 <!ENTITY uuml   CDATA "&#252;" -- small u, dieresis or umlaut mark -->
 <!ENTITY yacute CDATA "&#253;" -- small y, acute accent -->
 <!ENTITY thorn  CDATA "&#254;" -- small thorn, Icelandic -->
 <!ENTITY yuml   CDATA "&#255;" -- small y, dieresis or umlaut mark -->


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7.3.2. BIDI Entity Set

   The following entity set is sufficient to support the full Unicode
   bidirectionnal algorithm.

   <!-- Character entity set. Typical invocation:
        <!ENTITY % HTMLbidi PUBLIC
          "-//IETF//ENTITIES bidi//EN//HTML">
        %HTMLbidi;
     -->
   <!ENTITY zwnj SDATA "&#8204;"--=zero width non-joiner-->
   <!ENTITY zwj  SDATA "&#8205;"--=zero width joiner-->
   <!ENTITY lrm  SDATA "&#8206;"--=left-to-right mark-->
   <!ENTITY rlm  SDATA "&#8207;"--=right-to-left mark-->
   <!ENTITY lre  SDATA "&#8234;"--=left-to-right embedding-->
   <!ENTITY rle  SDATA "&#8235;"--=right-to-left embedding-->
   <!ENTITY pdf  SDATA "&#8236;"--=pop directional formatting-->
   <!ENTITY lro  SDATA "&#8237;"--=left-to-right override-->
   <!ENTITY rlo  SDATA "&#8238;"--=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 reprsentation des noms de


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                  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.  Units SI et recommandations pour
                  l'emploi de leurs multiples et de certaines autres
                  units.

   [ISO-3166]     ISO 3166:1993. Codes pour la reprsentation des noms
                  de pays.

   [ISO-4217]     ISO 4217:1990. Codes pour la reprsentation des mon-
                  naies et types des fonds.

   [ISO-8601]     ISO 8601:1988.  lments de donnes et formats
                  d'change -- change d'information -- Reprsentation
                  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.


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   [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

   Franois Yergeau
   Alis Technologies
   3410, rue Griffith
   Montral  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


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   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


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