Network Working Group F. Yergeau
Internet Draft G. Nicol
<draft-ietf-html-i18n-01.txt> G. Adams
Expires 30 March 1996 M. Duerst
25 September 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
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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, through var-
ious 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=2.1" 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 2.1 document character set ........................ 7
2.3. Undisplayable characters ................................... 8
3. Language tags .................................................. 8
4. Additional entities, attributes and elements ...................10
4.1. Full Latin-1 entity set ....................................10
4.2. Markup for language-dependent presentation .................10
5. Forms ..........................................................12
5.1. DTD additions ..............................................12
5.2. Form submission ............................................13
6. Miscellaneous ..................................................14
7. HTML public text ...............................................15
7.1. HTML DTD ...................................................15
7.2. SGML declaration for HTML ..................................30
7.3. Entity sets ................................................31
7.3.1. ISO Latin 1 character entity set .......................31
Bibliography ......................................................34
Authors' Addresses ................................................36
1. Introduction
The Hypertext Markup Language (HTML) is a simple markup language used
to create hypertext documents that are platform independent. Ini-
tially, the application of HTML on the World Wide Web was seriously
restricted by its reliance on the ISO-8859-1 coded character set,
which is appropriate only for Western European languages. Despite
this restriction, HTML has been widely used with other languages,
using other coded character sets or character encodings, through var-
ious ad hoc extensions to the language [TAKADA].
This document is meant to address the issue of the
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internationalization of HTML by extending the specification of HTML
2.0 and giving additional recommendations for proper internationali-
sation support. It is in good part based on a paper by one of the
authors on multilingualism on the WWW [NICOL]. A foremost considera-
tion 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 2.1".
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 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=2.1". 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
(see 7.1, "HTML DTD").
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* 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 within the range of the
Basic Multilingual Plane (BMP) of ISO 10646-1 [ISO-10646].
NOTE -- To support non-western writing systems, HTML user
agents are encouraged to support `UNICODE-1-1' or similar
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.
An HTML user agent is a level 2 user agent if, additionally:
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* 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
2.1, 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] of the "Content-Type" field of
the header of an HTTP response. For example, to indicate that the
transmitted document is encoded in the "JIS" encoding of Japanese
[RFC1468], the header will contain the following line:
Content-Type: text/html; charset=ISO-2022-JP
_________________________
[1] The term "charset" in MIME is used to designate a
character encoding, rather than a coded character set
as the term may suggest. A character encoding is a
mapping (possibly many-to-one) of a sequence of octets
to a sequence of characters taken from one or more
character repertoires. A coded character set is a map-
ping between individual bit patterns and individual
characters from a single character repertoire.
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The default charset 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 specify
the character encodings it can accept. Clients and servers are
strongly requested to use these mechanisms to assure correct trans-
mission and interpretation of any document. Provisions that can be
taken to help correct interpretation, even in cases where a server or
client do not yet use these mechanisms, are described in section 6.
Similarly, if HTML documents are transferred by electronic mail, the
character encoding is defined by the "charset" parameter of the "Con-
tent-Type" MIME header line [RFC1521].
In the case any other way of transferring and storing HTML documents
are defined or become popular, it is advised that similar provisions
should be made to clearly identify the character encoding used and/or
to use a single/default encoding capable of representing the widest
range of characters used in an international context.
Whatever the external character encoding actually be, the reference
processing model translates it to a representation of the document
character set specified in Section 2.2 before processing specific to
SGML/HTML. The reference processing model can be depicted as fol-
lows:
[resource]->[decoder]->[entity ]->[ SGML ]->[application]->[display]
[manager] [parser]
^ |
| |
+----------+
The decoder is responsible for decoding the external representation
of the resource to a representation using the document character set.
The entity manager, the parser, and the application deal only with
characters of the document character set. A display-oriented part of
the application or the display machinery itself may again convert
characters represented in the document character set to some other
representation more suitable for their purpose. In any case, the
entity manager, the parser, and the application, as far as character
semantics are concerned, are using the HTML 2.1 document character
set only.
An actual implementation may choose, or not, to translate the docu-
ment into some encoding of the document character set as described
above; the behaviour described by this reference processing model can
be achieved otherwise. This subject is well out of the scope of this
specification, however, and the reader is invited to consult the SGML
standard [ISO-8879] or a SGML handbook [BRYAN88] [GOLD90] [VANH90]
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[SQ91] for 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 2.1 document character set
The document character set, in the SGML sense, of HTML 2.1 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 65374 160
Making UCS-2 the document character set does not create non-
conformance of any expression, construct or document that is conform-
ing to HTML 2.0. It does make conforming certain constructs that are
not admissible in HTML 2.0. One consequence is that data characters
outside the repertoire of ISO-8859-1, but within that of UCS-2 become
valid SGML characters. Another is that the upper limit of the range
of numeric character references is extended from 255 to 65533[2] ;
thus, И is a valid reference to a "CYRILLIC CAPITAL LETTER I".
[ERCS] is a good source of information on Unicode and SGML, although
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 2.1. 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 the "Ethnologue" [ETHNO] (the latter is in addition
to the requirements of RFC 1766). Any two-letter initial subtag is an
ISO 3166 country code [ISO-3166].
In the context of HTML, a language tag is not to be interpreted as a
single token, as per RFC 1766, but as a hierarchy. For example, a
user agent that adjusts rendering according to language should con-
sider that it has a match when a language tag in a style sheet entry
matches the initial portion of the language tag of an element. An
exact match should be preferred. This interpretation allows an ele-
ment marked up as, for instance, "en-US" to trigger styles corre-
sponding to, in order of preference, US-English ("en-US") or 'plain'
or 'international' English ("en").
NOTE -- using the language tag as a hierarchy does not
imply that all languages with a common prefix will be
understood by those fluent in one or more of those lan-
guages; it simply allows the user to request this commonal-
ity when it is true for that user.
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 rendering of elements is meant to be controlled (in part) by the
LANG attribute. Specific user preferences set within the browser
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.
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4. Additional entities, attributes 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. Markup for language-dependent presentation
For the correct presentation of text from certain languages (irre-
spective of formatting issues), some support in the form of addi-
tional entities and elements is needed. 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. Plain text may contain this markup in the form of special-
purpose characters; in HTML, these are replaced by SGML markup to be
described below.
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. It is for this reason that these spe-
cial characters were added to Unicode (and, thence, to ISO/IEC
10646). If it were possible to do reliable layout and rendering of
bidirectionnal text without them, they definitely would not have been
included in Unicode.
First, a set of named character entities is added that allows partial
support of the Unicode bidirectional algorithm [UNICODE], plus some
help with languages requiring contextual analysis for rendering:
<!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-->
The first two, zwnj and zwj, are 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 system); 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
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provide that context. In Farsi texts, there are cases where a letter
that normally would join a subsequent letter in a cursive connection
does not. Here the ZWNJ is used.
The other two, lrm and rlm, are 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 directional property (but no word/line break
property).
Next, an attribute called DIR is introduced, restricted to the values
LTR and RTL and admitted by most elements. On block-type elements,
the DIR attribute indicates the base directionnality of the text in
the block; if omitted it is inherited from the parent element. On
inline elements, it makes the element start a new embedding level; if
omitted the inline element does not start a new embedding level.
Embedding is used to handle nested directional runs; 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
embedded pastings. 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 (LRE is shorthand for <SPAN DIR=LTR>, RLE for <SPAN
DIR=RTL> and PDF for </SPAN>):
LRE A B RLE a b LRE C D PDF c d PDF E F PDF
One gets the following rendering (with [] showing the
directional transitions):
[ A B [ d c [ C D ] b a ] E F ]
On the other hand, without these characters, e.g., with
A B a b C D c d E F
and a base level of LTR one gets the following rendering:
[ A B [ b a ] C D [ d c ] E F ]
Notice that b,a is on the left and d,c on the right unlike
the above case where the embedding levels are used. With-
out the embedding characters one has at most two levels: a
base directional level and a single counterflow directional
level.
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A directionnal override feature is needed to deal with
unusual pieces of text in which directionality cannot be
resolved from context in an unambiguous fashion. For exam-
ple, 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 this effect, 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.
A few other additional elements are important to have for
proper language-dependent rendering. First, a generic con-
tainer is needed to carry the LANG and BIDI attributes in
cases where no other element is appropriate; the SPAN ele-
ment is introduced for that purpose.
Short quotations, and in particular the quotation marks
surrounding them, are typically rendered differently in
different languages and on platforms with different graphic
capabilities: "a quotation in English", `another, slightly
better one', ,,a quotation in German", << a quotation in
French >>. The <Q> element is introduced for that purpose.
Many languages, including English, require superscripts for
proper rendering: "the XXth century" should have "th" 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 ele-
ments where it makes sense (block-like).
5. Forms
5.1. DTD additions
It is natural to expect input in any language in forms, as they pro-
vide one of the only ways of obtaining user input. While this is pri-
marily a UI issue, there are some things that should be specified at
the HTML level to guide behavior and promote interoperability.
To ensure interoperability, it is necessary for the user agent (and
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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.
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;
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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
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).
When HTML text is transmitted directly in UCS-2
(charset=UNICODE-1-1), the question of byte order arises: does the
high-order byte of each two-byte character come first or second? For
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definiteness, this specification recommends that UCS-2 be transmitted
in big-endian byte order (high order byte first), which corresponds
both to the established network byte order for two-byte quantities
and to the Unicode recommendation for serialized text data. Further-
more, to maximize chances of proper interpretation, it is recommended
that documents transmitted as UCS-2 always begin with a ZERO-WIDTH
NON-BREAKING SPACE character (hexadecimal FEFF) which, when byte-
reversed becomes number FFFE, a character guaranteed to be never
assigned. Thus, a user-agent receiving an FFFE as the first octets
of a text would know that bytes have to be reversed for the remainder
of the text.
7. HTML Public Text
7.1. HTML DTD
<!-- html-2.1.dtd
Document Type Definition for the HyperText Markup Language,
version 2.1 (HTML DTD)
Last revised: 95/09/25
Authors: Daniel W. Connolly <connolly@w3.org>
Francois Yergeau <yergeau@alis.com>
-->
<!ENTITY % HTML.Version
"-//IETF//DTD HTML 2.1//EN"
-- Typical usage:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.1//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
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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
-->
<!--============== 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
-->
<!--========= 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 --">
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<!ENTITY % just -- an attribute for text justification --
"ALIGN (left|right|center|justify) #IMPLIED">
<!--======= Character mnemonic entities =================-->
<!ENTITY % ISOlat1 PUBLIC
"ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
%ISOlat1;
<!--Entities for markup significant characters -->
<!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-->
<!ENTITY rlm CDATA "‏"-- right-to-left mark-->
<!--========= 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"
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-- 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"
>
<!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 -->
<!ENTITY % pre.content "#PCDATA|A|HR|BR|%font|%phrase|SPAN|BDO">
]]>
<!ENTITY % text "#PCDATA|A|IMG|BR|SPAN|Q|BDO|SUP|SUB">
<!-- Should the BDO element have an SDAFORM attr.? Which? -->
<!ELEMENT BDO - - (%text)+>
<!ATTLIST BDO
LANG NAME #IMPLIED
DIR (ltr|rtl) #REQUIRED
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>
<!-- <BDO> Control bidirectionnal text -->
<!ELEMENT BR - O EMPTY>
<!ATTLIST BR
%SDAPREF; "&#RE;"
>
<!-- <BR> Line break -->
<!-- Should the SPAN element have an SDAFORM attr.? Which? -->
<!ELEMENT SPAN - - (%text)*>
<!ATTLIST SPAN
%attrs;
>
<!-- <SPAN> Generic container -->
<!ELEMENT Q - - (%text)*>
<!ATTLIST Q
%attrs;
%SDAFORM; "It" -- to be verified --
>
<!-- <Q> Short quotation -->
<!ELEMENT (SUP|SUB) - - (#PCDATA)>
<!ATTLIST (SUP|SUB)
%attrs;
>
<!-- <SUP> Superscript -->
<!-- <SUB> Subscript -->
<!--========= 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
">
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<![ %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)*">
<!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) -->
<!--========== 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 ISMAP> Each pixel can be a link -->
<!--========== Paragraphs=======================-->
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<!ELEMENT P - O (%text)*>
<!ATTLIST P
%attrs;
%just;
%SDAFORM; "Para"
>
<!-- <P> Paragraph -->
<!--========== Headings, Titles, Sections ===============-->
<!ELEMENT HR - O EMPTY>
<!ATTLIST HR
%attrs;
%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"
>
<!ATTLIST H6
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%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 -->
<![ %HTML.Deprecated [
<!ENTITY % literal "CDATA"
-- historical, non-conforming parsing mode where
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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>
<!ATTLIST DD
%attrs;
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%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 -->
<!-- <MENU COMPACT> Compact list style -->
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<!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 -->
<!ELEMENT BLOCKQUOTE - - %body.content>
<!ATTLIST BLOCKQUOTE
%attrs;
%just;
%SDAFORM; "BQ"
>
<!-- <BLOCKQUOTE> Quoted passage -->
<!ELEMENT ADDRESS - - (%text|P)*>
<!ATTLIST ADDRESS
%attrs;
%just;
%SDAFORM; "Lit"
%SDAPREF; "Address:&#RE;"
>
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<!-- <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"
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 | 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 --
%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 -->
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<!-- <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
%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 -->
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]]>
<!--======= 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) -->
<!-- <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 -->
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<!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;
%SDAFORM; "Book"
>
<!-- <HTML> HTML Document -->
7.2. SGML Declaration for HTML
<!SGML "ISO 8879:1986"
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--
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
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
NAMING LCNMSTRT ""
UCNMSTRT ""
LCNMCHAR ".-"
UCNMCHAR ".-"
NAMECASE GENERAL YES
ENTITY NO
DELIM GENERAL SGMLREF
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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. 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:
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<!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 -->
<!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 -->
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<!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 -->
<!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 -->
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<!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>
[ETHNO] "Ethnologue, Languages of the World", 12th Edition,
Barbara F. Grimes editor, Summer Institute of Linguis-
tics, Dallas, 1992.
[FILE-UPLOAD] E. Nebel and L. Masinter, "Form-based File Upload in
HTML", Work in progress (draft-ietf-html-
fileupload-03.txt), Xerox Corporation, August 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-05.txt), MIT/W3C, August 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
langue. Technical content in
<http://www.sil.org/sgml/iso639a.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
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monnaies 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.
[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.
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[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
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
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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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