Network Working Group F. Yergeau
Internet Draft G. Nicol
<draft-ietf-html-i18n-04.txt> G. Adams
Expires 2 December 1996 M. Duerst
27 May 1996
Internationalization of the Hypertext Markup Language
Status of this Memo
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Abstract
The Hypertext Markup Language (HTML) is a simple markup language used
to create hypertext documents that are platform independent. Ini-
tially, the application of HTML on the World Wide Web was seriously
restricted by its reliance on the ISO-8859-1 coded character set,
which is appropriate only for Western European languages. Despite
this restriction, HTML has been widely used with other languages,
using other coded character sets or character encodings, at the
expense of interoperability.
This document is meant to address the issue of the
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internationalization (i18n, i followed by 18 letters followed by n)
of HTML by extending the specification of HTML and giving additional
recommendations for proper internationalization support. A foremost
consideration is to make sure that HTML remains a valid application
of SGML, while enabling its use in all languages of the world.
Table of contents
1. Introduction .................................................. 2
1.1. Scope ...................................................... 3
1.2. Conformance ................................................ 3
2. The document character set ..................................... 4
2.1. Reference processing model ................................. 4
2.2. The document character set ................................. 6
2.3. Undisplayable characters ................................... 8
3. The LANG attribute.............................................. 8
4. Additional entities, attributes and elements ................... 9
4.1. Full Latin-1 entity set .................................... 9
4.2. Markup for language-dependent presentation ................. 9
5. Forms ..........................................................15
5.1. DTD additions ..............................................15
5.2. Form submission ............................................15
6. Miscellaneous ..................................................17
7. HTML public text ...............................................18
7.1. HTML DTD ...................................................18
7.2. SGML declaration for HTML ..................................34
7.3. ISO Latin 1 character entity set ...........................35
Bibliography ......................................................38
Authors' Addresses ................................................40
1. Introduction
The Hypertext Markup Language (HTML) is a simple markup language used
to create hypertext documents that are platform independent. Ini-
tially, the application of HTML on the World Wide Web was seriously
restricted by its reliance on the ISO-8859-1 coded character set,
which is appropriate only for Western European languages. Despite
this restriction, HTML has been widely used with other languages,
using other coded character sets or character encodings, through var-
ious ad hoc extensions to the language [TAKADA].
This document is meant to address the issue of the internationaliza-
tion of HTML by extending the specification of HTML and giving addi-
tional recommendations for proper internationalization support. It
is in good part based on a paper by one of the authors on multilin-
gualism on the WWW [NICOL]. A foremost consideration is to make sure
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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
some additional elements and 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 1866), primarily by removing the restriction to the
ISO-8859-1 coded character set [ISO-8859-1].
HTML is an application of ISO Standard 8879:1986, Information Pro-
cessing Text and Office Systems -- Standard Generalized Markup Lan-
guage (SGML) [ISO-8879]. The HTML Document Type Definition (DTD) is a
formal definition of the HTML syntax in terms of SGML. This specifi-
cation amends the DTD of HTML in order to make it applicable to docu-
ments encompassing a character repertoire much larger than that of
ISO-8859-1, while still remaining SGML conformant.
Both formal and actual development of HTML are advancing very fast.
The features described in this document are designed so that they can
(and should) be added to other forms of HTML besides that described
in RFC 1866. Where indicated, attributes introduced here should be
extended to the appropriate elements.
1.2 Conformance
This specification changes slightly the conformance requirements of
HTML documents and HTML user agents.
1.2.1 Documents
All HTML 2.0 conforming documents remain conforming with this speci-
fication. However, the extensions introduced here make valid cer-
tains documents that would not be HTML 2.0 conforming, in particular
those containing characters or character references outside of the
repertoire of ISO 8859-1, and those containing markup introduced
herein.
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1.2.2. User agents
In addition to the requirements of RFC 1866, the following require-
ments are placed on HTML user agents.
To ensure interoperability and proper support for at least
ISO-8859-1 in an environment where character encoding schemes
other than ISO-8859-1 are present, user agents must correctly
interpret the charset parameter accompanying an HTML document
received from the network.
Furthermore, conforming user-agents are required to at least parse
correctly all numeric character references within the range of ISO
10646-1 [ISO-10646].
Conforming user-agents are required to apply the BIDI presentation
algorithm if they display right-to-left characters. If there is
no displayable right-to-left character in a document, there is no
need to apply BIDI processing.
2. The document character set
2.1. Reference processing model
This overview explains a reference processing model used for HTML,
and in particular the SGML concept of a document character set. An
actual implementation may widely differ in its internal workings from
the model given below, but should behave as described to an outside
observer.
Because there are various widely differing encodings of text, SGML
does not directly address the question of how characters are encoded
e.g. in a file. SGML views the characters as a single set (called a
"character repertoire"), and a "code set" that assigns an integer
number (known as "character number") to each character in the reper-
toire. The document character set declaration defines what each of
the character numbers represents [GOLD90, p. 451]. In most cases, an
SGML DTD and all documents that refer to it have a single document
character set, and all markup and data characters are part of this
set.
HTML, as an application of SGML, does not directly address the ques-
tion of how characters are encoded as octets in external representa-
tions such as files. This is deferred to mechanisms external to HTML,
such as MIME as used by the HTTP protocol or by electronic mail.
For the HTTP protocol [RFC1945], the way characters are encoded is
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defined by the "charset" parameter[1] of the "Content-Type" field of
the header of an HTTP response. For example, to indicate that the
transmitted document is encoded in the "JIS" encoding of Japanese
[RFC1468], the header will contain the following line:
Content-Type: text/html; charset=ISO-2022-JP
The HTTP protocol also defines a mechanism for the client to specify
the character encodings it can accept. Clients and servers are
strongly requested to use these mechanisms to assure correct trans-
mission and interpretation of any document. Provisions that can be
taken to help correct interpretation, even in cases where a server or
client do not yet use these mechanisms, are described in section 6.
Similarly, if HTML documents are transferred by electronic mail, the
character encoding is defined by the "charset" parameter of the "Con-
tent-Type" MIME header line [RFC1521], and defaults to US-ASCII in
its absence.
In the case any other way of transferring and storing HTML documents
are defined or become popular, it is advised that similar provisions
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 may be, the reference pro-
cessing model translates it to a representation of the document char-
acter set specified in Section 2.2 before processing specific to
SGML/HTML. The reference processing model can be depicted as fol-
lows:
[resource]->[decoder]->[entity ]->[ SGML ]->[application]->[display]
[manager] [parser]
^ |
| |
+----------+
The decoder is responsible for decoding the external representation
of the resource to a representation using the document character set.
The entity manager, the parser, and the application deal only with
characters of the document character set. A display-oriented part of
the application or the display machinery itself may again convert
-----------
1 The term "charset" in MIME is used to designate a char-
acter encoding, rather than a coded character set as the
term may suggest. A character encoding is a mapping (possi-
bly many-to-one) of a sequence of octets to a sequence of
characters taken from one or more character repertoires.
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characters represented in the document character set to some other
representation more suitable for their purpose. In any case, the
entity manager, the parser, and the application, as far as character
semantics are concerned, are using the HTML document character set
only.
An actual implementation may choose, or not, to translate the docu-
ment into some encoding of the document character set as described
above; the behaviour described by this reference processing model can
be achieved otherwise. This subject is well out of the scope of this
specification, however, and the reader is invited to consult the SGML
standard [ISO-8879] or an SGML handbook [BRYAN88] [GOLD90] [VANH90]
[SQ91] for further information.
The most important consequence of this reference processing model is
that numeric character references are always resolved with respect to
the fixed document character set, and thus to the same characters,
whatever the external encoding actually used. For an example, see
Section 2.2.
2.2. The document character set
The document character set, in the SGML sense, is the Universal Char-
acter Set (UCS) of ISO 10646:1993 [ISO-10646], as amended. Cur-
rently, this is code-by-code identical with the Unicode standard,
version 1.1 [UNICODE].
NOTE -- implementers should be aware that ISO 10646 is
amended from time to time; 4 amendments have been adopted
since the initial 1993 publication, none of which signifi-
cantly affects this specification. A fifth amendment, now
under consideration, will introduce incompatible changes to
the standard: 6556 Korean Hangul syllables allocated
between code positions 3400 and 4DFF (hexadecimal) will be
moved to new positions (and 4516 new syllables added), thus
making references to the old positions invalid. Since the
Unicode consortium has already adopted a corresponding
amendment for inclusion in the forthcoming Unicode 2.0,
adoption of DAM 5 is considered likely and implementers
should probably consider the old code positions as already
invalid. Despite this one-time change, the relevant stan-
dard bodies appear to remain committed not to change any
allocated code position in the future. To encode Korean
Hangul irrespective of these changes, the combining Hangul
Jamo in the range 1110-11F9 can be used.
The adoption of this document character set implies a change in the
SGML declaration specified in the HTML 2.0 specification (section 9.5
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of [RFC1866]). The change amounts to removing the first BASESET
specification and its accompanying DESCSET declaration, replacing
them with the following declaration:
BASESET "ISO Registration Number 177//CHARSET
ISO/IEC 10646-1:1993 UCS-4 with implementation level 3
//ESC 2/5 2/15 4/6"
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 2147483486 160
Making the UCS 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-4 become
valid SGML characters. Another is that the upper limit of the range
of numeric character references is extended from 255 to 2147483645;
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 specifica-
tion.
NOTE -- the above SGML declaration, like that of HTML 2.0,
specifies the character numbers 128 to 159 (80 to 9F hex)
as UNUSED. This means that numeric character references
within that range (e.g. ’) are illegal in HTML. Nei-
ther ISO 8859-1 nor ISO 10646 contain characters in that
range, which is reserved for control characters.
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. 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.
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2.3. Undisplayable characters
With the document character set being the full ISO 10646, the possi-
bility that a character cannot be displayed due to lack of appropri-
ate resources (fonts) cannot be avoided. Because there are many dif-
ferent things that can be done in such a case, this document does not
prescribe any specific behaviour. Depending on the implementation,
this may also be handled by the underlaying display system and not
the application itself. The following considerations, however, may
be of help:
- A clearly visible, but unobtrusive behaviour should be preferred.
Some documents may contain many characters that cannot be renden-
dered, and so showing an alert for each of them is not the right
thing to do.
- In case a numeric representation of the missing character is
given, its hexadecimal (not decimal) form is to be preferred,
because this form is used in character set standards [ERCS].
3. The LANG attribute
Language tags can be used to control rendering of a marked up docu-
ment in various ways: glyph disambiguation, in cases where the char-
acter encoding is not sufficient to resolve to a specific glyph; quo-
tation marks; hyphenation; ligatures; spacing; voice synthesis; etc.
Independently of rendering issues, language markup is useful as con-
tent markup for purposes such as classification and searching.
Since any text can logically be assigned a language, almost all HTML
elements admit the LANG attribute. The DTD reflects this. It is
also intended that any new element introduced in later versions of
HTML will admit the LANG attribute, unless there is a good reason not
to do so.
The language attribute, LANG, takes as its value a language tag that
identifies a natural language spoken, written, or otherwise conveyed
by human beings for communication of information to other human
beings. Computer languages are explicitly excluded.
The syntax and registry of HTML language tags is the same as that
defined by RFC 1766 [RFC1766]. In summary, a language tag is composed
of one or more parts: A primary language tag and a possibly empty
series of subtags:
language-tag = primary-tag *( "-" subtag )
primary-tag = 1*8ALPHA
subtag = 1*8ALPHA
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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
In the context of HTML, a language tag is not to be interpreted as a
single token, as per RFC 1766, but as a hierarchy. For example, a
user agent that adjusts rendering according to language should con-
sider that it has a match when a language tag in a style sheet entry
matches the initial portion of the language tag of an element. An
exact match should be preferred. This interpretation allows an ele-
ment marked up as, for instance, "en-US" to trigger styles corre-
sponding to, in order of preference, US-English ("en-US") or 'plain'
or 'international' English ("en").
NOTE -- using the language tag as a hierarchy does not
imply that all languages with a common prefix will be
understood by those fluent in one or more of those lan-
guages; it simply allows the user to request this commonal-
ity when it is true for that user.
The rendering of elements may be affected by the LANG attribute. For
any element, the value of the LANG attribute overrides the value
specified by the LANG attribute of any enclosing element and the
value (if any) of the HTTP Content-Language header. If none of these
are set, a suitable default, perhaps controlled by user preferences,
by automatic context analysis or by the user's locale, should be used
to control rendering.
4. Additional entities, attributes and elements
4.1. Full Latin-1 entity set
According to the suggestion of section 14 of [RFC1866], the set of
Latin-1 entities is extended to cover the whole right part of
ISO-8859-1 (all code positions with the high-order bit set), includ-
ing the already commonly used , © and ®. The names of
the entities are taken from the appendices of SGML [ISO-8879]. A
list is provided in section 7.3 of this specification.
4.2. Markup for language-dependent presentation
4.2.1. Overview
For the correct presentation of text in certain languages (irrespec-
tive of formatting issues), some support in the form of additional
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entities and elements is needed.
In particular, the following features are dealt with:
- Markup of bidirectional text, i.e. text where left-to-right and
right-to-left scripts are mixed.
- Control of cursive joining behaviour in contexts where the default
behaviour is not appropriate.
- Language-dependent rendering of short (in-line) quotations.
- Better justification control for languages where this is impor-
tant.
- Superscripts and subscripts for languages where they appear as
part of general text.
Some of the above features need very little additional support; oth-
ers need more. The additional features are introduced below with
brief comments only. Explanations on cursive joining behaviour and
bidirectional text follow later. For cursive joining behaviour and
bidirectional text, this document follows [UNICODE] in that: i) char-
acter semantics, where applicable, are identical to [UNICODE], and
ii) where functionality is moved to HTML as a higher level protocol,
this is done in a way that allows straightforward conversion to the
lower-level mechanisms defined in [UNICODE].
4.2.2. List of entities, elements, and attributes
First, a generic container is needed to carry the LANG and DIR (see
below) attributes in cases where no other element is appropriate; the
SPAN element is introduced for that purpose.
A set of named character entities is added for use with bidirectional
rendering and cursive joining control:
<!ENTITY zwnj CDATA "‌"--=zero width non-joiner-->
<!ENTITY zwj CDATA "‍"--=zero width joiner-->
<!ENTITY lrm CDATA "‎"--=left-to-right mark-->
<!ENTITY rlm CDATA "‏"--=right-to-left mark-->
These entities can be used in place of the corresponding formatting
characters whenever convenient, for example to ease keyboard entry or
when a formatting character is not available in the character encod-
ing of the document.
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Next, an attribute called DIR is introduced, restricted to the values
LTR (left-to-right) and RTL (right-to-left) and admitted by most ele-
ments, for the indication of directionality in the context of bidi-
rectional text (see 4.2.4 below for details). Since any text and
many other elements (e.g. tables) can logically be assigned a direc-
tionality, almost all HTML elements admit the DIR attribute. The DTD
reflects this. It is also intended that any new element introduced
in later versions of HTML will admit the DIR attribute, unless there
is a good reason not to do so.
A new element called BDO (BIDI Override) is introduced, which
requires the DIR attribute to specify whether the override is left-
to-right or right-to-left. This element is required for bidirec-
tional text control; for detailed explanations, see section 4.2.4.
The <Q> element is introduced to allow language-dependent rendering
of short quotations depending on language and platform capability.
As the following examples show, in particular the quotation marks
surrounding the quotation are affected: "a quotation in English",
`another, slightly better one', ,,a quotation in German'', << a quo-
tation in French >>. The contents of the <Q> element does not
include quotation marks, they have to be added by the rendering pro-
cess.
NOTE -- <Q> elements can be nested. Many languages use dif-
ferent quotation styles for outer and inner quotations, and
this should be respected by user-agents implementing this
element.
Many languages require superscripts for proper rendering: as an exam-
ple, the French "Mlle Dupont" should have "lle" in superscript. The
<SUP> element, and its sibling <SUB>, are introduced to allow proper
markup of such text. <SUP> and <SUB> contents are restricted to
PCDATA to avoid nesting problems.
Finally, in many languages text justification is much more important
than it is in Western languages, and justifies markup. The ALIGN
attribute, admitting values of LEFT, RIGHT, CENTER and JUSTIFY, is
added to a selection of elements where it makes sense (block-like).
If a user-agent chooses to have LEFT as a default for blocks of left-
to-right directionality, it should use RIGHT for blocks of right-to-
left directionality.
In the DTD, the LANG and DIR attributes are grouped together in a
parameter entity called attrs. In addition, the ID and CLASS
attributes from RFC 1942 [RFC1942] were added to attrs, as was done
in the latter. The ID, and CLASS attributes are required for use with
style sheets, and RFC 1942 defines them as follows:
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ID Used to define a document-wide identifier. This can be used
for naming positions within documents as the destination of a
hypertext link. It may also be used by style sheets for ren-
dering an element in a unique style. An ID attribute value is
an SGML NAME token. NAME tokens are formed by an initial let-
ter followed by letters, digits, "-" and "." characters. The
letters are restricted to A-Z and a-z.
CLASS A space separated list of SGML NAME tokens. CLASS names spec-
ify that the element belongs to the corresponding named
classes. It allows authors to distinguish different roles
played by the same tag. The classes may be used by style
sheets to provide different renderings as appropriate to
these roles.
4.2.3. Cursive joining behaviour
Markup is needed in some cases to force cursive joining behavior in
contexts in which it would not normally occur, or to block it when it
would normally occur.
The zero-width joiner and non-joiner (‍ and ‌) are used to
control cursive joining behaviour. For example, ARABIC LETTER HEH is
used in isolation to abbreviate "Hijri" (the Islamic calendrical sys-
tem); however, the initial form of the letter is desired, because the
isolated form of HEH looks like the digit five as employed in Arabic
script. This is obtained by following the HEH with a zero-width
joiner whose only effect is to provide context. In Persian texts,
there are cases where a letter that normally would join a subsequent
letter in a cursive connection does not. Here a zero-width non-
joiner is used.
4.2.4. Bidirectional text
Many languages are written in horizontal lines from left to right,
while others are written from right to left. When both writing
directions are present, one talks of bidirectional text (BIDI for
short). BIDI text requires markup in special circumstances where
ambiguities as to the directionality of some characters have to be
resolved. This markup affects the ability to render BIDI text in a
semantically legible fashion. That is, without this special BIDI
markup, cases arise which would prevent *any* rendering whatsoever
that reflected the basic meaning of the text. Plain text may contain
this markup (joining or BIDI) in the form of special-purpose charac-
ters; in HTML, these are supplemented by SGML markup.
BIDI is a complex issue, and implementers are advised to consult
appropriate documentation such as [UNICODE]. Here, explanations are
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given only as far as they are needed to understand the necessity of
the features introduced and to define their exact semantics.
The Unicode BIDI algorithm is based on a logical sequence of text
characters and works mainly by reference to the implicit directional-
ity of characters (e.g. Hebrew and Arabic characters are specified to
be rendered from right to left, etc.).
The left-to-right and right-to-left marks (‎ and ‏) are used
to disambiguate directionality of neutral characters. For example,
when a double quote sits between an Arabic and a Latin letter, its
direction is ambiguous; if a directional mark is added on one side
such that the quotation mark is surrounded by characters of only one
directionality, the ambiguity is removed. These characters are like
zero width spaces which have a directional property (but no word/line
break property).
Nested embeddings of contra-directional text runs, due to nested quo-
tations or to the pasting of text from one BIDI context to another,
is also a case where the implicit directionality of characters is not
sufficient, requiring markup. Also, it is frequently desirable to
specify the basic directionality of a block of text. For these pur-
poses, the DIR attribute is used.
On block-type elements, the DIR attribute indicates the base direc-
tionality of the text in the block; if omitted it is inherited from
the parent element. The default directionality of the overall HTML
document is left-to-right.
On inline elements, it makes the element start a new embedding level
(to be explained below); if omitted the inline element does not start
a new embedding level.
NOTE -- the PRE, XMP and LISTING elements admit the DIR
attribute, indicating that the contents should not be con-
sidered as preformatted with respect to bidirectional lay-
out. The BIDI algorithm still needs to be applied to each
line of text.
Following is an example of a case where embedding is needed, showing
its effect:
Given the following latin (upper case) and arabic (lower
case) letters in backing store with the specified embed-
dings:
<SPAN DIR=LTR> AB <SPAN DIR=RTL> xy <SPAN DIR=LTR> CD
</SPAN> zw </SPAN> EF </SPAN>
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One gets the following rendering (with [] showing the
directional transitions):
[ AB [ wz [ CD ] yx ] EF ]
On the other hand, without this markup and with a base
direction of LTR one gets the following rendering:
[ AB [ yx ] CD [ wz ] EF ]
Notice that yx is on the left and wz on the right unlike
the above case where the embedding levels are used. With-
out the embedding markup one has at most two levels: a base
directional level and a single counterflow directional
level.
The DIR attribute on inline elements is equivalent to the formatting
characters LEFT-TO-RIGHT EMBEDDING (202A) and RIGHT-TO-LEFT EMBED-
DING (202B) of ISO 10646. The end tag of the element is equivalent
to the POP DIRECTIONAL FORMATTING (202C) character.
Directional override, as provided by the <BDO> element, is needed to
deal with unusual short pieces of text in which directionality cannot
be resolved from context in an unambiguous fashion. For example, it
can be used to force left-to-right (or right-to-left) display of part
numbers composed of Latin letters, digits and Hebrew letters.
The effect of <BDO> is to force the directionality of all characters
within it to the value of DIR, irrespective of their intrinsic direc-
tional properties. It is equivalent to using the LEFT-TO-RIGHT OVER-
RIDE (202D) or RIGHT-TO-LEFT OVERRIDE (202E) characters of ISO 10646,
the end tag again being equivalent to the POP DIRECTIONAL FORMATTING
(202C) character.
NOTE -- authors and authoring software writers should be
aware that conflicts can arise if the DIR attribute is used
on inline elements (including <BDO>) concurrently with the
use of the corresponding ISO 10646 formatting characters.
Preferably one or the other should be used exclusively; the
markup method is better able to guarantee document struc-
tural integrity, and alleviates some problems when editing
bidirectional HTML text with a simple text editor, but some
software may be more apt at using the 10646 characters. If
both methods are used, great care should be exercised to
insure proper nesting of markup and directional embedding
or override; otherwise, rendering results are undefined.
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5. Forms
5.1. DTD additions
It is natural to expect input in any language in forms, as they pro-
vide one of the only ways of obtaining user input. While this is pri-
marily a UI issue, there are some things that should be specified at
the HTML level to guide behavior and promote interoperability.
To ensure full interoperability, it is necessary for the user agent
(and the user) to have an indication of the character encoding(s)
that the server providing a form will be able to handle upon submis-
sion of the filled-in form. Such an indication is provided by the
ACCEPT-CHARSET attribute of the INPUT and TEXTAREA elements, modeled
on the HTTP Accept-Charset header (see [HTTP-1.1]), which contains a
space and/or comma delimited list of character sets acceptable to the
server. A user agent may want to somehow advise the user of the con-
tents of this attribute, or to restrict his possibility to enter
characters outside the repertoires of the listed character sets.
NOTE -- The list of character sets is to be interpreted as
an EXCLUSIVE-OR list; the server announces that it is ready
to accept any ONE of these character encoding schemes for
each part of a multipart entity. The client may perform
character encoding translation to satisfy the server if
necessary.
NOTE -- The default value for the ACCEPT-CHARSET attribute
of an INPUT or TEXTAREA element is the reserved value
"UNKNOWN". A user agent may interpret that value as the
character encoding scheme that was used to transmit the
document containing that element.
5.2. Form submission
The HTML 2.0 form submission mechanism, based on the "application/x-
www-form-urlencoded" media type, is ill-equipped with regard to
internationalization. In fact, since URLs are restricted to ASCII
characters, the mechanism is akward even for ISO-8859-1 text. Sec-
tion 2.2 of [RFC1738] specifies that octets may be encoded using the
"%HH" notation, but text submitted from a form is composed of charac-
ters, not octets. Lacking a specification of a character encoding
scheme, the "%HH" notation has no well-defined meaning.
The best solution is to use the "multipart/form-data" media type
described in [RFC1867] with the POST method of form submission. This
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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.
A less satisfactory solution is to add a MIME charset parameter to
the "application/x-www-form-urlencoded" media type specifier sent
along with a POST method form submission, with the understanding that
the URL encoding of [RFC1738] is applied on top of the specified
character encoding, as a kind of implicit Content-Transfer-Encoding.
One problem with both solutions above is that current browsers do not
generally allow for bookmarks to specify the POST method; this should
be improved. Conversely, the GET method could be used with the form
data transmitted in the body instead of in the URL. Nothing in the
protocol seems to prevent it, but no implementations appear to exist
at present.
How the user agent determines the encoding of the text entered by the
user is outside the scope of this specification.
NOTE -- Designers of forms and their handling scripts
should be aware of an important caveat: when the default
value of a field (the VALUE attribute) is returned upon
form submission (i.e. the user did not modify this value),
it cannot be guaranteed to be transmitted as a sequence of
octets identical to that in the source document -- only as
a possibly different but valid encoding of the same
sequence of text elements. This may be true even if the
encoding of the document containing the form and that used
for submission are the same.
Differences can occur when a sequence of characters can be
represented by various sequences of octets, and also when a
composite sequence (a base character plus one or more com-
bining diacritics) can be represented by either a different
but equivalent composite sequence or by a fully precomposed
character. For instance, the UCS-2 sequence 00EA+0232
(LATIN SMALL LETTER E WITH CIRCUMFLEX ACCENT + COMBINING
DOT BELOW) may be transformed into 1EC7 (LATIN SMALL LETTER
E WITH CIRCUMFLEX ACCENT AND DOT BELOW), into
0065+0302+0323 (LATIN SMALL LETTER E + COMBINING CIRCUMFLEX
ACCENT + COMBINING DOT BELOW), as well as into other equiv-
alent composite sequences.
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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. This is bad behaviour[2], 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 is possible 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. Note that there are better ways for a server to
obtain character encoding information, instead of the unreliable
<META> above; see [NICOL2] for some details and a proposal.
For definiteness, the "charset" parameter received from the source of
the document should be considered the most authoritative, followed in
order of preference by the contents of a META element such as the
above, and finally the CHARSET parameter of the anchor that was fol-
lowed (if any).
When HTML text is transmitted directly in UCS-2 or UCS-4 form, the
question of byte order arises: does the high-order byte of each
multi-byte character come first or last? For definiteness, this
specification recommends that UCS-2 and UCS-4 be transmitted in big-
-----------
2 This bad behaviour is even encouraged by the continued
existence of browsers that declare an unrecognized media
type when they receive a charset parameter. User agent
implementators are strongly encouraged to make their soft-
ware tolerant of this parameter, even if they cannot take
advantage of it.
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endian byte order (high order byte first), which corresponds to the
established network byte order for two- and four-byte quantities, to
the Unicode recommendation for serialized text data and to RFC 1641.
Furthermore, to maximize chances of proper interpretation, it is rec-
ommended that documents transmitted as UCS-2 or UCS-4 always begin
with a ZERO-WIDTH NON-BREAKING SPACE character (hexadecimal FEFF or
0000FEFF) which, when byte-reversed becomes number FFFE or FFFE0000,
a character guaranteed to be never assigned. Thus, a user-agent
receiving an FFFE as the first octets of a text would know that bytes
have to be reversed for the remainder of the text.
There exist so-called UCS Transformation Formats than can be used to
transmit UCS data, in addition to UCS-2 and UCS-4. UTF-7 [RFC1642]
and UTF-8 [UTF-8] have favorable properties (no byte-ordering prob-
lem, different flavours of ASCII compatibility) that make them worthy
of consideration, especially for transmission of multilingual text.
Another encoding scheme, MNEM [RFC1345], also has interesting proper-
ties and the capability to transmit the full UCS. The UTF-1 trans-
formation format of ISO 10646:1993 (registered by IANA as
ISO-10646-UTF-1), has been removed from ISO 10646 by amendment 4, and
should not be used.
The SOFT HYPHEN character (U+00AD) needs a little attention from
user-agent implementers. It is present in many character sets
(including the whole ISO 8859 series and, of course, ISO 10646), and
has semantics different from the plain HYPHEN. If not used for
hyphenation, the soft hyphen must be completely ignored. For exam-
ple, "rec­ord" should display as "record", should match a search
for "record", and should sort as "record". Non-observance of these
semantics effectively discourages its use on the World Wide Web, even
with software that does support it.
7. HTML Public Text
7.1. HTML DTD
This section contains a DTD for HTML based on the HTML 2.0 DTD of RFC
1866, incorporating the changes for file upload as specified in RFC
1867, and the changes deriving from this document.
<!-- html.dtd
Document Type Definition for the HyperText Markup Language,
extended for internationalisation (HTML DTD)
Last revised: 96/05/27
Authors: Daniel W. Connolly <connolly@w3.org>
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Francois Yergeau <yergeau@alis.com>
See Also: html.decl, html-1.dtd
http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
-->
<!ENTITY % HTML.Version
"-//IETF//DTD HTML//EN"
-- Typical usage:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//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.
-->
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<!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
-->
<!--============== 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, RFC1945
-->
<!--========= 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 --
DIR (ltr|rtl) #IMPLIED -- text directionnality --
ID ID #IMPLIED -- element identifier (from RFC1942) --
CLASS NAMES #IMPLIED -- for subclassing elements (from RFC1942) --">
<!ENTITY % just -- an attribute for text justification --
"ALIGN (left|right|center|justify) #IMPLIED"
-- default is left for ltr paragraphs, right for rtl -- >
<!--======= Character mnemonic entities =================-->
<!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 -->
<!--Entities for language-dependent presentation (BIDI and contextual analysis) -->
<!ENTITY zwnj CDATA "‌"-- zero width non-joiner-->
<!ENTITY zwj CDATA "‍"-- zero width joiner-->
<!ENTITY lrm CDATA "‎"-- left-to-right mark-->
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<!ENTITY rlm CDATA "‏"-- right-to-left mark-->
<!--========= SGML Document Access (SDA) Parameter Entities =====-->
<!-- HTML 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 -->
<!--========== Text Markup =====================-->
<![ %HTML.Highlighting [
<!ENTITY % font " TT | B | I ">
<!ENTITY % phrase "EM | STRONG | CODE | SAMP | KBD | VAR | CITE ">
<!ENTITY % text "#PCDATA|A|IMG|BR|%phrase|%font|SPAN|Q|BDO|SUP|SUB">
<!ELEMENT (%font;|%phrase) - - (%text)*>
<!ATTLIST ( TT | CODE | SAMP | KBD | VAR )
%attrs;
%SDAFORM; "Lit"
>
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<!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 substitutable -->
<!-- <CITE> Name or title of cited work -->
<!ENTITY % pre.content "#PCDATA|A|HR|BR|%font|%phrase|SPAN|BDO">
]]>
<!ENTITY % text "#PCDATA|A|IMG|BR|SPAN|Q|BDO|SUP|SUB">
<!ELEMENT BR - O EMPTY>
<!ATTLIST BR
%SDAPREF; "&#RE;"
>
<!-- <BR> Line break -->
<!ELEMENT SPAN - - (%text)*>
<!ATTLIST SPAN
%attrs;
%SDAFORM; "other #Attlist"
>
<!-- <SPAN> Generic inline container -->
<!-- <SPAN DIR=...> New counterflow embedding -->
<!-- <SPAN LANG="..."> Language of contents -->
<!ELEMENT Q - - (%text)*>
<!ATTLIST Q
%attrs;
%SDAPREF; '"'
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%SDASUFF; '"'
>
<!-- <Q> Short quotation -->
<!-- <Q LANG=xx> Language of quotation is xx -->
<!-- <Q DIR=...> New conterflow embedding -->
<!ELEMENT BDO - - (%text)+>
<!ATTLIST BDO
LANG NAME #IMPLIED
DIR (ltr|rtl) #REQUIRED
%SDAPREF "Bidi Override #Attval(DIR): "
%SDASUFF "End Bidi"
>
<!-- <BDO DIR=...> Override directionality of text to value of DIR -->
<!-- <BDO LANG=...> Language of contents -->
<!ELEMENT (SUP|SUB) - - (#PCDATA)>
<!ATTLIST (SUP)
%attrs;
%SDAPREF "Superscript(#content)"
>
<!ATTLIST (SUB)
%attrs;
%SDAPREF "Subscript(#content)"
>
<!-- <SUP> Superscript -->
<!-- <SUB> Subscript -->
<!--========= Link Markup ======================-->
<!ENTITY % linkType "NAMES">
<!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
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<a name="xxx"><H1>Heading</H1></a>
-->
]]>
<!ENTITY % A.content "(%heading|%text)*">
<!ELEMENT A - - %A.content -(A)>
<!ATTLIST A
%attrs;
HREF CDATA #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 METHODS="..."> Operations on destination (advisory) -->
<!-- <A CHARSET="..."> Charset of destination (advisory) -->
<!-- <A LANG="..."> Language of contents btw <A> and </A> -->
<!-- <A DIR=...> Contents is a new counterflow embedding -->
<!--========== Images ==========================-->
<!ELEMENT IMG - O EMPTY>
<!ATTLIST IMG
%attrs;
SRC CDATA #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 LANG=...> Image contains "text" in that language -->
<!-- <IMG DIR=rtl> Inline image acts as a right-to-left
embedding w/r to BIDI algorithm -->
<!-- <IMG ISMAP> Each pixel can be a link -->
<!--========== Paragraphs=======================-->
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<!ELEMENT P - O (%text)*>
<!ATTLIST P
%attrs;
%just;
%SDAFORM; "Para"
>
<!-- <P> Paragraph -->
<!-- <P LANG="..."> Language of paragraph text -->
<!-- <P DIR=...> Base directionality of paragraph -->
<!-- <P ALIGN=...> Paragraph alignment (justification) -->
<!--========== Headings, Titles, Sections ===============-->
<!ELEMENT HR - O EMPTY>
<!ATTLIST HR
%just;
%SDAPREF; "&#RE;&#RE;"
>
<!-- <HR> Horizontal rule -->
<!ELEMENT ( %heading ) - - (%text;)*>
<!ATTLIST H1
%attrs;
%just;
%SDAFORM; "H1"
>
<!ATTLIST H2
%attrs;
%just;
%SDAFORM; "H2"
>
<!ATTLIST H3
%attrs;
%just;
%SDAFORM; "H3"
>
<!ATTLIST H4
%attrs;
%just;
%SDAFORM; "H4"
>
<!ATTLIST H5
%attrs;
%just;
%SDAFORM; "H5"
>
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<!ATTLIST H6
%attrs;
%just;
%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">
]]>
<!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 | SPAN | BDO">
<!ELEMENT PRE - - (%pre.content)*>
<!ATTLIST PRE
%attrs;
WIDTH NUMBER #implied
%SDAFORM; "Lit"
>
<!-- <PRE> Preformatted text -->
<!-- <PRE WIDTH=...> Maximum characters per line -->
<!-- <PRE DIR=...> Base direction of preformatted block -->
<!-- <PRE LANG=...> Language of contents -->
<![ %HTML.Deprecated [
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<!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 -->
<!-- <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>
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<!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;
%just;
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
>
<!ATTLIST UL
%attrs;
%just;
COMPACT (COMPACT) #IMPLIED
%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;
%just;
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
%SDAPREF; "<LHead>Directory</LHead>"
>
<!ATTLIST MENU
%attrs;
%just;
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
%SDAPREF; "<LHead>Menu</LHead>"
>
<!-- <DIR> Directory list -->
<!-- <DIR COMPACT> Compact list style -->
<!-- <MENU> Menu list -->
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<!-- <MENU COMPACT> Compact list style -->
<!ELEMENT LI - O %flow>
<!ATTLIST LI
%attrs;
%just;
%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)*">
<!ELEMENT BODY O O %body.content>
<!ATTLIST BODY
%attrs;
>
<!-- <BODY> Document body -->
<!-- <BODY DIR=...> Base direction of whole body -->
<!-- <BODY LANG=...> Language of contents -->
<!ELEMENT BLOCKQUOTE - - %body.content>
<!ATTLIST BLOCKQUOTE
%attrs;
%just;
%SDAFORM; "BQ"
>
<!-- <BLOCKQUOTE> Quoted passage -->
<!ELEMENT ADDRESS - - (%text|P)*>
<!ATTLIST ADDRESS
%attrs;
%just;
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%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 CDATA #IMPLIED
METHOD (%HTTP-Method) GET
ENCTYPE %Content-Type; "application/x-www-form-urlencoded"
%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 -->
<!-- <FORM DIR=...> Base direction of form -->
<!-- <FORM LANG=...> Language of contents -->
<!ENTITY % InputType "(TEXT | PASSWORD | CHECKBOX |
RADIO | SUBMIT | RESET |
IMAGE | HIDDEN | FILE )">
<!ELEMENT INPUT - O EMPTY>
<!ATTLIST INPUT
%attrs;
TYPE %InputType TEXT
NAME CDATA #IMPLIED
VALUE CDATA #IMPLIED
SRC CDATA #IMPLIED
CHECKED (CHECKED) #IMPLIED
SIZE CDATA #IMPLIED
MAXLENGTH NUMBER #IMPLIED
ALIGN (top|middle|bottom) #IMPLIED
ACCEPT CDATA #IMPLIED --list of content types --
ACCEPT-CHARSET CDATA #IMPLIED --list of charsets accepted by server --
%SDAPREF; "Input: "
>
<!-- <INPUT> Form input datum -->
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<!-- <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 -->
<!-- <INPUT ACCEPT="..."> List of desired media types -->
<!-- <INPUT ACCEPT-CHARSET="..."> List of acceptable charsets -->
<!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
%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
ACCEPT-CHARSET CDATA #IMPLIED -- list of charsets accepted by server --
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%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)>
<!ATTLIST HEAD
%attrs; >
<!-- <HEAD> Document head -->
<!ELEMENT TITLE - - (#PCDATA)* -(META|LINK)>
<!ATTLIST TITLE
%attrs;
%SDAFORM; "Ti" >
<!-- <TITLE> Title of document -->
<!ELEMENT LINK - O EMPTY>
<!ATTLIST LINK
%attrs;
HREF CDATA #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) -->
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<!-- <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 CDATA #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 Meta-information -->
<!-- <META HTTP-EQUIV=...> HTTP response header name -->
<!-- <META NAME=...> Meta-information name -->
<!-- <META CONTENT="..."> Associated information -->
<!--======= 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;
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%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 = HTML 2.0 + i18n).
--
CHARSET
BASESET "ISO Registration Number 177//CHARSET
ISO/IEC 10646-1:1993 UCS-4 with
implementation level 3//ESC 2/5 2/15 4/6"
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 2147483486 160
CAPACITY SGMLREF
TOTALCAP 150000
GRPCAP 150000
ENTCAP 150000
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 646:1983//CHARSET
International Reference Version
(IRV)//ESC 2/5 4/0"
DESCSET 0 128 0
FUNCTION
RE 13
RS 10
SPACE 32
TAB SEPCHAR 9
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NAMING LCNMSTRT ""
UCNMSTRT ""
LCNMCHAR ".-"
UCNMCHAR ".-"
NAMECASE GENERAL YES
ENTITY NO
DELIM GENERAL SGMLREF
SHORTREF SGMLREF
NAMES SGMLREF
QUANTITY SGMLREF
ATTSPLEN 2100
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. ISO Latin 1 entity set
The following public text lists each of the characters specified in
the Added Latin 1 entity set, along with its name, syntax for use,
and description. This list is derived from ISO Standard
8879:1986//ENTITIES Added Latin 1//EN. HTML includes the entire
entity set, and adds entities for all missing characters in the right
part of ISO-8859-1.
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<!-- (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;
-->
<!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 -->
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<!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 -->
<!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 -->
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<!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 -->
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>
[GOLD90] C. F. Goldfarb, "The SGML Handbook", Y. Rubinsky, Ed.,
Oxford University Press, 1990.
[HTTP-1.1] R.T. Fielding, H. Frystyk Nielsen, and T. Berners-Lee,
"Hypertext Transfer Protocol -- HTTP/1.1", Work in
progress (draft-ietf-http-v11-spec-03.txt), MIT/LCS,
May 1996.
[ISO-639] ISO 639:1988. Codes pour la représentation des noms de
langue. Technical content in
<http://www.sil.org/sgml/iso639a.html>
[ISO-3166] ISO 3166:1993. Codes pour la représentation des noms
de pays.
[ISO-8601] ISO 8601:1988. Éléments de données et formats
d'échange -- Échange d'information -- Représentation
de la date et de l'heure.
[ISO-8859-1] ISO 8859-1:1987. International Standard -- Informa-
tion Processing -- 8-bit Single-Byte Coded Graphic
Character Sets -- Part 1: Latin Alphabet No. 1.
[ISO-8879] ISO 8879:1986. International Standard -- Information
Processing -- Text and Office Systems -- Standard Gen-
eralized Markup Language (SGML).
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[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>
[NICOL2] G.T. Nicol, "MIME Header Supplemented File Type", Work
in progress, <draft-nicol-mime-header-type-00.txt>,
EBT, October 1995.
[RFC1345] K. Simonsen, "Character Mnemonics & Character Sets",
RFC 1345, Rationel Almen Planlaegning, June 1992.
[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.
[RFC1641] D. Goldsmith, M.Davis, "Using Unicode with MIME", RFC
1641, Taligent inc., July 1994.
[RFC1642] D. Goldsmith, M. Davis, "UTF-7: A Mail-safe Transfor-
mation Format of Unicode", RFC 1642, Taligent inc.,
July 1994.
[RFC1738] T. Berners-Lee, L. Masinter, and M. McCahill, "Uniform
Resource Locators (URL)", RFC 1738, CERN, Xerox PARC,
University of Minnesota, October 1994.
[RFC1766] H. Alverstrand, "Tags for the Identification of Lan-
guages", RFC 1766, UNINETT, March 1995.
[RFC1866] T. Berners-Lee and D. Connolly, "Hypertext Markup Lan-
guage - 2.0", RFC 1866, MIT/W3C, November 1995.
[RFC1867] E. Nebel and L. Masinter, "Form-based File Upload in
HTML", RFC 1867, Xerox Corporation, November 1995.
[RFC1942] D. Raggett, "HTML Tables", RFC 1942, W3C, May 1996.
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[RFC1945] T. Berners-Lee, R.T. Fielding, and H. Frystyk Nielsen,
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
MIT/LCS, UC Irvine, May 1996.
[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, and Technical
Report #4, 1993. The BIDI algorithm is in appendix A
of volume 1, with corrections in appendix D of volume
2.
[UTF-8] ISO/IEC 10646-1:1993 AMENDMENT 2 (1996). UCS Transfor-
mation Format 8 (UTF-8).
[VANH90] E. van Hervijnen, "Practical SGML", Kluwer Academicq
Publishers Group, Norwell and Dordrecht, 1990.
Authors' Addresses
François Yergeau
Alis Technologies
100, boul. Alexis-Nihon, bureau 600
Montréal QC H4M 2P2
Canada
Tel: +1 (514) 747-2547
Fax: +1 (514) 747-2561
EMail: fyergeau@alis.com
Gavin Thomas Nicol
Electronic Book Technologies, Japan
1-29-9 Tsurumaki,
Setagaya-ku,
Tokyo
Japan
Tel: +81-3-3230-8161
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Fax: +81-3-3230-8163
EMail: gtn@ebt.com, gtn@twics.co.jp
Glenn Adams
Spyglass
118 Magazine Street
Cambridge, MA 02139
U.S.A.
Tel: +1 (617) 864-5524
Fax: +1 (617) 864-4965
EMail: glenn@spyglass.com
Martin J. Duerst
Multimedia-Laboratory
Department 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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