Hypertext Markup Language (HTML) Tim Berners-Lee, CERN Internet Draft Daniel Connolly, Atrium IIIR Working Group June 1993
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Distribution of this document is unlimited. The document is a draft form of a standard for interchange of information on the network which is proposed to be registered as a MIME (RFC1341) content type. Please send comments to timbl@info.cern.ch or the discussion list www-talk@info.cern.ch.
This is version 1.2 of this draft. This document is available in hypertext on the World-Wide Web as http://info.cern.ch/hypertext/WWW/MarkUp/HTML.html
HTML is proposed as a MIME content type.
HTML refers to the URL specification of RFCxxxx.
Implementations of HTML parsers and generators can be found in the various W3 servers and browsers, in the public domain W3 code, and may also be built using various public domain SGML parsers such as [SGMLS] . HTML is an SGML document type with fairly generic semantics appropriate for representing information from a wide range of applications. It is more generic than many specific SGML applications, but is still completely device-independent.
MIME Type name text
MIME subtype name: html
Required parameters: none
Optional parameters: charset
When an HTML document is encoded using 7-bit characters, then the mechanisms of character references and entity references may be used to encode characters in the upper half of the ISO Latin-1 set. In this way, documents may be prepared which are suitable for mailing through 7-bit limited systems.
Every SGML document has three parts:
All HTML documents share the same SGML declaration an prologue. Hence implementations of the WorldWide Web generally only transmit and store the instance part of an HTML document. To construct an SGML document entity for processing by an SGML parser, it is necessary to prefix the text from ``HTML DTD'' on page 10 to the HTML instance.
Conversely, to implement an HTML parser, one need only implement those parts of an SGML parser that are needed to parse an instance after parsing the HTML DTD.
The instance represents a hierarchy of elements. Each element has a name , some attributes , and some content. Most elements are represented in the document as a start tag, which gives the name and attributes, followed by the content, followed by the end tag. For example:
<HTML>
<TITLE>
A sample HTML instance
</TITLE>
<H1>
An Example of Structure
</H1>
Here's a typical paragraph.
<P>
<UL>
<LI>
Item one has an
<A NAME="anchor">
anchor
</A>
<LI>
Here's item two.
</UL>
</HTML>
Some elements (e.g. P, LI) are empty. They have no content. They
show up as just a start tag.
For the rest of the elements, the content is a sequence of data characters and nested elements. Note that the HTML DTD in fact severely limits the amount of nesting which is allowed: most things cannot be nested, in fact. No elements may be recursively nested. Anchors and character highlighting may be put inside other constructs.
The value is specified in a string surrounded by single quotes or a string surrounded by double quotes. (See: other tolerated forms @@)
The string is parsed like RCDATA (see below) to determine the attribute value. This allows, for example, quote characters in attribute values to be represented by character references.
The length of an attribute value (after parsing) is limited to 1024 characters.
<!ELEMENT NEXTID - O EMPTY>
<!ATTLIST NEXTID N NUMBER #REQUIRED>
This means that the following:
<nextid n=''27''>
is legal, but these others are not:
<nextid>
<nextid n=''abc''>
<!ELEMENT XMP - - CDATA>specifies that the following text is a legal XMP element:
<xmp>Here's an example. It looks like it has
<tags> and <!--comments-->
in it, but it does not. Even this
</ is data.</xmp>
The string </ is only recognized as the opening delimiter of an end
tag when it is ``in context,'' that is, when it is followed by a
letter. However, as soon as the end tag open delimiter is
recognized, it terminates the CDATA content. The following is an
error:
<xmp>There is no way to represent </end> tags
in CDATA </xmp>
<!ELEMENT TITLE - - RCDATA>can have any sequence of characters in their content.
<title>You can even represent </end> tags in RCDATA </title>
The string & signals an entity reference when it is followed by a letter or a digit. The delimiter is followed by the entity name and a semicolon. For example:
Kurt Gödel was a famous logician and mathematician.
Whitespace in element content is considered markup and ignored. Any characters that are not markup, that is, data characters, are illegal.
For example:
<!ELEMENT HEAD - - (TITLE? & ISINDEX? & NEXTID? & LINK*)>declares an element that may be used as follows:
<head> <isindex> <title>Head Example</title> </head>But the following are illegal:
<head> no data allowed! </head> <head><isindex><title>Two isindex tags</title><isindex></head>
<!ELEMENT PRE - - (#PCDATA | A | B | I | U | P)+>
<!ATTLIST PRE
WIDTH NUMBER #implied
>
This says that the PRE element contains one or more A, B, I, U, or
P elements or data characters. Here's an example of a PRE element:
<pre>
<b>NAME</b>
cat -- concatenate<a href=''terms.html#file''>files</a>
<b>EXAMPLE</b>
cat <xyz
</pre>
The content of the above PRE element is:
A B element
The string `` cat -- concatenate''
An A element
The string ``\n''
Another B element
The string ``\n cat <xyz''
For example:
<HEAD> <TITLE>HTML Guide: Recommended Usage</TITLE> <!-- $Id: recommended.html,v 1.3 93/01/06 18:38:11 connolly Exp $ --> </HEAD>There are a few other SGML markup constructs that are deprecated or illegal.
Delimiter Signals...
<? Processing instruction. Terminated by >.
<![ Marked section. Marked sections are
deprecated. See the SGML standard for
complete information.
<! Markup declaration. HTML defines no short
reference maps, so these are errors.
Terminated by >.
<PRE>some example text</pre>or
<pre> some example text </pre>and these will be processed identically.
Also, a line that's not empty but contains no content will be ignored altogether. For example, the element
<pre> <!-- this line is ignored, including the linebreak character --> first line third line<!-- the following linebreak is content: --> fourth line<!-- this one's ignored because it's the last piece of cont ent: --> </pre>contains only the strings
first line third line fourth line.
The rendering of a horizontal tab (HT) character is not defined, and HT should therefore not be used, except within a PRE (or obsolete XMP, LISTING or PLAINTEXT) element.
Neither spaces nor tabs should be used to make SGML source layout more attractive or easier to read.
The following delimiters may signal markup, depending on context. Delimiter Signals <!-- Comment &# Character reference & Entity reference </ End tag <! Markup declaration ]]> Marked section close (an error) < Start tag
Old style documents may contain a just the contents of the normal HEAD and BODY elements, in any order. This is deprecated but must be supported by parsers.
See also: Status of elements
The elements within the BODY element are in the order in which they should be presented to the reader.
See the list of things which are allowed within a BODY element.
The text between the opening tag and the closing tag is either the start or destination (or both) of a link. Attributes of the anchor tag are as follows.
See <A HREF="http://info.cern.ch/">CERN</A>'s information for
more details.
A <A NAME=serious>serious</A> crime is one which is associated
with imprisonment.
...
The Organization may refuse employment to anyone convicted
of a <A href="#serious">serious</A> crime.
The format of URNs is under discussion (1993) by various working groups of the Internet Engineering Task Force.
<ADDRESS><A HREF="Author.html">A.N.Other</A></ADDRESS>
<ADDRESS>
Newsletter editor<p>
J.R. Brown<p>
JimquickPost News, Jumquick, CT 01234<p>
Tel (123) 456 7890
</ADDRESS>
Where the base address is not specified, the reader will use the URL it used to access the document to resolve any relative URLs.
The one attribute is:
Single-font rendition may for example put a vertical line of ">" characters down the left margin to indicate quotation in the Internet mail style.
A heading element implies all the font changes, paragraph breaks before and after, and white space (for example) necessary to render the heading. Further character emphasis or paragraph marks are not required in HTML.
H1 is the highest level of heading, and is recommended for the start of a hypertext node. It is suggested that the the text of the first heading be suitable for a reader who is already browsing in related information, in contrast to the title tag which should identify the node in a wider context.
The heading elements are
<H1>, <H2>, <H3>, <H4>, <H5>, <H6>
It is not normal practice to jump from one header to a header level
more than one below, for example for follow an H1 with an H3.
Although this is legal, it is discouraged, as it may produce
strange results for example when generating other representations
from the HTML.
<H1>This is a heading</H1>
Here is some text
<H2>Second level heading</H2>
Here is some more text.
The rendering software is responsible for generating suitable vertical white space between elements, so it is NOT normal or required to follow a heading element with a paragraph mark.
The IMG element allows another document to be inserted inline. The document is normally an icon or small graphic, etc. This element is NOT intended for embedding other HTML text.
Browsers which are not able to display inline images ignore IMG elements. Authors should note that some browsers will be able to display (or print) linked graphics but not inline graphics. If the graphic is essential, it may be wiser to make a link to it rather than to put it inline. If the graphic is essentially decorative, then IMG is appropriate.
The IMG element is empty: it has no closing tag. It has three attributes:
Warning: < IMG SRC ="triangle.gif" ALT="Warning:"> This must b
e done by a
qualified technician.
< A HREF="Go">< IMG SRC ="Button"> Press to start</A>
The node may be queried with a keyword search by suffixing the node address with a question mark, followed by a list of keywords separated by plus signs. See the network address format .
Note that this tag is normally generated automatically by a server. If it is added by hand to an HTML document, then the client will assume that the server can handle a search on the document.
Obviously the server must have this capability for it to work: simply adding <ISINDEX> in the document is not enough to make searches happen if the server does not have a search engine!
Status: standard.
<ISINDEX>
The LINK element is empty, but takes the same attributes as the anchor element .
Typical uses are to indicate authorship, related indexes and glossaries, older or more recent versions, etc. Links can indicate a static tree structure in which the document was authored by pointing to a "parent" and "next" and "previous" document, for example.
Servers may also allow links to be added by those who do not have the right to alter the body of a document.
The definition list DT, DD pairs are arranged vertically. For each pair, the DT element is on the left, in a column of about a third of the display area, and the DD element is in the right hand two thirds of the display area. The DT term is normally small enough to fit on one line within the left-hand column. If it is longer, it will either extend across the page, in which case the DD section is moved down to separate them, or it is wrapped onto successive lines of the left hand column.
White space is typically left between successive DT,DD pairs unless the COMPACT attribute is given. The COMPACT attribute is appropriate for lists which are long and/or have DT,DD pairs which each take only a line or two. It is of course possible for the rendering software to discover these cases itself and make its own decisions, and this is to be encouraged. The COMPACT attribute may also reduce the width of the left-hand (DT) column.
<DL>
<DT>Term the first<DD>definition paragraph is reasonably
long but is still displayed clearly
<DT>Term2 follows<DD>Definition of term2
</DL>
<DL COMPACT>
<DT>Term<DD>definition paragraph
<DT>Term2<DD>Definition of term2
</DL>
<UL>
<LI> list element
<LI> another list element ...
</UL>
The opening list tag may be any of UL, OL, MENU or DIR. It must
be immediately followed by the first list element.
List elements with typical rendering are:
<OL>
<LI> When you get to the station, leave
by the southern exit, on platform one.
<LI>Turn left to face toward the mountain
<LI>Walk for a mile or so until you reach the
"Asquith Arms" then
<LI>Wait and see...
</OL>
< MENU >
<LI>The oranges should be pressed fresh
<LI>The nuts may come from a packet
<LI>The gin must be good quality
</MENU>
< DIR >
<LI>A-H<LI>I-M
<LI>M-R<LI>S-Z
</DIR>
When modifying a document, old anchor ids should not be reused, as there may be references stored elsewhere which point to them. This is read and generated by hypertext editors. Human writers of HTML usually use mnemonic alphabetical identifiers. Browser software may ignore this tag.
<NEXTID N=27>
<P> is used between two pieces of text which otherwise would be flowed together.
You do NOT need to use <P> to put white space around heading, list, address or blockquote elements which imply a paragraph break. It is the responsibility of the rendering software to generate that white space. A paragraph mark which is preceded or followed by such elements which imply a paragraph break is has undefined effect and should be avoided.
<h1>What to do</h1>
This is a one paragraph.< p >This is a second.
< P >
This is a third.
<h1><P>What not to do</h1>
<p>I found that on my XYZ browser it looked prettier to
me if I put some paragraph marks
<p>
<ul><p><li>Around lists, and
<li>After headings.
</ul>
<p>
None of the paragraph marks in this example should
be there.
The optional attribute is:
<PRE WIDTH="80">
This is an example line
</PRE>
Note: Highlighting
Within a preformatted element, the constraint that the rendering must be on a fixed horizontal character pitch may limit or prevent the ability of the renderer to render highlighting elements specially.
Note: Margins
The above references to the "beginning of a new line" must not be taken as implying that the renderer is forbidden from using a (constant) left indent for rendering preformatted text. The left indent may of course be constrained by the width required.
There may only be one title in any document. It should identify the content of the document in a fairly wide context.
The title is not part of the text of the document, but is a property of the whole document. It may not contain anchors, paragraph marks, or highlighting. The title may be used to identify the node in a history list, to label the window displaying the node, etc. It is not normally displayed in the text of a document itself. Contrast titles with headings . The title should ideally be less than 64 characters in length. That is, many applications will display document titles in window titles, menus, etc where there is only limited room. Whilst there is no limit on the length of a title (as it may be automatically generated from other data), information providers are warned that it may be truncated if long.
<TITLE>Rivest and Neuman. 1989(b)</TITLE>
or
<TITLE>A Recipe for Maple Syrup Flap-Jack</TITLE>
or
<TITLE>Introduction -- AFS user's Guide</TITLE>
Examples of inappropriate titles are those which are only
meaningful within context,
<TITLE>Introduction</TITLE>
or too long,
<TITLE>Remarks on the Quantum-Gravity effects of "Bean
Pole" diversification in Mononucleosis patients in Developing
Countries under Economic Conditions Prevalent during
the Second half of the Twentieth Century, and Related Papers:
a Summary</TITLE>
These elements allow sections of text to be formatted in a particular way, to provide emphasis, etc. The tags do NOT cause a paragraph break, and may be used on sections of text within paragraphs.
Where not supported by implementations, like all tags, these tags should be ignored but the content rendered.
All these tags have related closing tags, as in
This is <EM>emphasized</EM> text.
Some of these styles are more explicit than others about how they
should be physically represented. The logical styles should be
used wherever possible, unless for example it is necessary to refer
to the formatting in the text. (Eg, "The italic parts are
mandatory".)
Note:
Browsers unable to display a specified style may render it in some alternative, or the default, style, with some loss of quality for the reader. Some implementations may ignore these tags altogether, so information providers should attempt not to rely on them as essential to the information content.
These element names are derived from TeXInfo macro names.
This text contains an <em>emphasized</em> word.
<strong>Don't assume</strong> that it will be italic!
It was made using the <CODE>EM</CODE> element. A citation is
typically italic and has no formal necessary structure:
<cite>Moby Dick</cite> is a book title.
The empty PLAINTEXT tag terminates the HTML entity. What follows is not SGML. In stead, there's an old HTTP convention that what follows is an ASCII (MIME "text/plain") body.
An example if its use is:
<PLAINTEXT>
0001 This is line one of a ling listing
0002 file from <any@host.inc.com> which is sen
This tag allows the rest of a file to be read efficiently without
parsing. Its presence is an optimization. There is no closing tag.
The rest of the data is not in SGML.
These styles allow text of fixed-width characters to be embedded absolutely as is into the document. The syntax is:
<LISTING>
...
</LISTING>
or
<XMP>
...
</XMP>
The text between these tags is to be portrayed in a fixed width
font, so that any formatting done by character spacing on
successive lines will be maintained. Between the opening and
closing tags:
<HP1>...</HP1> <HP2>... </HP2> etc.
A comment element used for bracketing off unneed text and comment has been introduced in some browsers but will be replaced by the SGML command feature in new implementations.
This form is not supported by SGML and so is not the specified HTML interpretation. Providers should be warned that implementations may vary on how they interpret end tags apparently within these elements
< The less than sign < > The "greater than" sign > & The ampersand sign & itself. " The double quote sign "Also allowed are references to any of the ISO Latin-1 alphabet, using the entity names in the following table.
Æ capital AE diphthong (ligature) Á capital A, acute accent  capital A, circumflex accent À capital A, grave accent Å capital A, ring à capital A, tilde Ä capital A, dieresis or umlaut mark Ç capital C, cedilla Ð capital Eth, Icelandic É capital E, acute accent Ê capital E, circumflex accent È capital E, grave accent Ë capital E, dieresis or umlaut mark Í capital I, acute accent Î capital I, circumflex accent Ì capital I, grave accent Ï capital I, dieresis or umlaut mark Ñ capital N, tilde Ó capital O, acute accent Ô capital O, circumflex accent Ò capital O, grave accent Ø capital O, slash Õ capital O, tilde Ö capital O, dieresis or umlaut mark Þ capital THORN, Icelandic Ú capital U, acute accent Û capital U, circumflex accent Ù capital U, grave accent Ü capital U, dieresis or umlaut mark Ý capital Y, acute accent á small a, acute accent â small a, circumflex accent æ small ae diphthong (ligature) à small a, grave accent å small a, ring ã small a, tilde ä small a, dieresis or umlaut mark ç small c, cedilla é small e, acute accent ê small e, circumflex accent è small e, grave accent ð small eth, Icelandic ë small e, dieresis or umlaut mark í small i, acute accent î small i, circumflex accent ì small i, grave accent ï small i, dieresis or umlaut mark ñ small n, tilde ó small o, acute accent ô small o, circumflex accent ò small o, grave accent ø small o, slash õ small o, tilde ö small o, dieresis or umlaut mark ß small sharp s, German (sz ligature) þ small thorn, Icelandic ú small u, acute accent û small u, circumflex accent ù small u, grave accent ü small u, dieresis or umlaut mark ý small y, acute accent ÿ small y, dieresis or umlaut mark
<!SGML "ISO 8879:1986"
--
Document Type Definition for the HyperText Markup Language
as used by the World Wide Web application (HTML DTD).
NOTE: This is a definition of HTML with respect to
SGML, and assumes an understanding of SGML terms.
--
CHARSET
BASESET "ISO 646:1983//CHARSET
International Reference Version (IRV)//ESC 2/5 4/0"
DESCSET 0 9 UNUSED
9 2 9
11 2 UNUSED
13 1 13
14 18 UNUSED
32 95 32
127 1 UNUSED
BASESET "ISO Registration Number 100//CHARSET
ECMA-94 Right Part of Latin Alphabet Nr. 1//ESC 2/13 4
/1"
DESCSET 128 32 UNUSED
160 95 32
255 1 UNUSED
CAPACITY SGMLREF
TOTALCAP 150000
GRPCAP 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
255
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
SHORTREF SGMLREF
NAMES SGMLREF
QUANTITY SGMLREF
NAMELEN 34
TAGLVL 100
LITLEN 1024
GRPGTCNT 150
GRPCNT 64
FEATURES
MINIMIZE
DATATAG NO
OMITTAG NO
RANK NO
SHORTTAG NO
LINK
SIMPLE NO
IMPLICIT NO
EXPLICIT NO
OTHER
CONCUR NO
SUBDOC NO
FORMAL YES
APPINFO NONE
>
<!DOCTYPE HTML [
<!-- Jul 1 93 -->
<!-- Regarding clause 6.1, SGML Document:
[1] SGML document = SGML document entity,
(SGML subdocument entity |
SGML text entity | non-SGML data entity)*
The role of SGML document entity is filled by this DTD,
followed by the conventional HTML data stream.
-->
<!-- DTD definitions -->
<!ENTITY % heading "H1|H2|H3|H4|H5|H6" >
<!ENTITY % list "UL|OL|DIR|MENU">
<!ENTITY % literal "XMP|LISTING">
<!ENTITY % headelement
"TITLE|NEXTID|ISINDEX" >
<!ENTITY % bodyelement
"P | %heading |
%list | DL | HEADERS | ADDRESS | PRE | BLOCKQUOTE
| %literal">
<!ENTITY % oldstyle "%headelement | %bodyelement | #PCDATA">
<!ENTITY % URL "CDATA"
-- The term URL means a CDATA attribute
whose value is a Uniform Resource Locator,
as defined. (A URN may also be usable here when defined.)
-->
<!ENTITY % linkattributes
"NAME NMTOKEN #IMPLIED
HREF %URL; #IMPLIED
REL CDATA #IMPLIED -- forward relationship type --
REV CDATA #IMPLIED -- reversed relationship type
to referent data:
PARENT CHILD, SIBLING, NEXT, TOP,
DEFINITION, UPDATE, ORIGINAL etc. --
URN CDATA #IMPLIED -- universal resource number --
TITLE CDATA #IMPLIED -- advisory only --
METHODS NAMES #IMPLIED -- supported public methods of the object:
TEXTSEARCH, GET, HEAD, ... --
">
<!-- Document Element -->
<!ELEMENT HTML O O (( HEAD | BODY | %oldstyle)*, PLAINTEXT?)>
<!ELEMENT HEAD - - (TITLE? & ISINDEX? & NEXTID? & LINK*
& BASE?)>
<!ELEMENT TITLE - - RCDATA
-- The TITLE element is not considered part of the flow of text.
It should be displayed, for example as the page header or
window title.
-->
<!ELEMENT ISINDEX - O EMPTY
-- WWW clients should offer the option to perform a search on
documents containing ISINDEX.
-->
<!ELEMENT NEXTID - O EMPTY>
<!ATTLIST NEXTID N NAME #REQUIRED
-- The number should be a name suitable for use
for the ID of a new element. When used, the value
has its numeric part incremented. EG Z67 becomes Z68
-->
<!ELEMENT LINK - O EMPTY>
<!ATTLIST LINK
%linkattributes>
<!ELEMENT BASE - O EMPTY -- Reference context for URLS -->
<!ATTLIST BASE
HREF %URL; #IMPLIED
>
<!ENTITY % inline "EM | TT | STRONG | B | I | U |
CODE | SAMP | KBD | KEY | VAR | DFN | CITE "
>
<!ELEMENT (%inline;) - - (#PCDATA)>
<!ENTITY % text "#PCDATA | IMG | %inline;">
<!ENTITY % htext "A | %text">
<!ELEMENT BODY - - (%bodyelement|%htext;)*>
<!ELEMENT A - - (%text)>
<!ATTLIST A
%linkattributes;
>
<!ELEMENT IMG - O EMPTY -- Embedded image -->
<!ATTLIST IMG
SRC %URL; #IMPLIED -- URL of document to embed --
>
<!ELEMENT P - O EMPTY -- separates paragraphs -->
<!ELEMENT ( %heading ) - - (%htext;)+>
<!ELEMENT DL - - (DT | DD | P | %htext;)*>
<!-- Content should match ((DT,(%htext;)+)+,(DD,(%htext;)+))
But mixed content is messy.
-->
<!ELEMENT DT - O EMPTY>
<!ELEMENT DD - O EMPTY>
<!ELEMENT (UL|OL) - - (%htext;|LI|P)+>
<!ELEMENT (DIR|MENU) - - (%htext;|LI)+>
<!-- Content should match ((LI,(%htext;)+)+)
But mixed content is messy.
-->
<!ATTLIST (%list)
COMPACT NAME #IMPLIED -- COMPACT, etc.--
>
<!ELEMENT LI - O EMPTY>
<!ELEMENT BLOCKQUOTE - - (%htext;|P)+
-- for quoting some other source -->
<!ELEMENT ADDRESS - - (%htext;|P)+>
<!ELEMENT PRE - - (#PCDATA|%inline|A|P)+>
<!ATTLIST PRE
WIDTH NUMBER #implied
>
<!-- Mnemonic character entities. -->
<!ENTITY AElig "Æ" -- capital AE diphthong (ligature) -->
<!ENTITY Aacute "Á" -- capital A, acute accent -->
<!ENTITY Acirc "Â" -- capital A, circumflex accent -->
<!ENTITY Agrave "À" -- capital A, grave accent -->
<!ENTITY Aring "Å" -- capital A, ring -->
<!ENTITY Atilde "Ã" -- capital A, tilde -->
<!ENTITY Auml "Ä" -- capital A, dieresis or umlaut mark -->
<!ENTITY Ccedil "Ç" -- capital C, cedilla -->
<!ENTITY ETH "Ð" -- capital Eth, Icelandic -->
<!ENTITY Eacute "É" -- capital E, acute accent -->
<!ENTITY Ecirc "Ê" -- capital E, circumflex accent -->
<!ENTITY Egrave "È" -- capital E, grave accent -->
<!ENTITY Euml "Ë" -- capital E, dieresis or umlaut mark -->
<!ENTITY Iacute "Í" -- capital I, acute accent -->
<!ENTITY Icirc "Î" -- capital I, circumflex accent -->
<!ENTITY Igrave "Ì" -- capital I, grave accent -->
<!ENTITY Iuml "Ï" -- capital I, dieresis or umlaut mark -->
<!ENTITY Ntilde "Ñ" -- capital N, tilde -->
<!ENTITY Oacute "Ó" -- capital O, acute accent -->
<!ENTITY Ocirc "Ô" -- capital O, circumflex accent -->
<!ENTITY Ograve "Ò" -- capital O, grave accent -->
<!ENTITY Oslash "Ø" -- capital O, slash -->
<!ENTITY Otilde "Õ" -- capital O, tilde -->
<!ENTITY Ouml "Ö" -- capital O, dieresis or umlaut mark -->
<!ENTITY THORN "Þ" -- capital THORN, Icelandic -->
<!ENTITY Uacute "Ú" -- capital U, acute accent -->
<!ENTITY Ucirc "Û" -- capital U, circumflex accent -->
<!ENTITY Ugrave "Ù" -- capital U, grave accent -->
<!ENTITY Uuml "Ü" -- capital U, dieresis or umlaut mark -->
<!ENTITY Yacute "Ý" -- capital Y, acute accent -->
<!ENTITY aacute "á" -- small a, acute accent -->
<!ENTITY acirc "â" -- small a, circumflex accent -->
<!ENTITY aelig "æ" -- small ae diphthong (ligature) -->
<!ENTITY agrave "à" -- small a, grave accent -->
<!ENTITY amp "&" -- ampersand -->
<!ENTITY aring "å" -- small a, ring -->
<!ENTITY atilde "ã" -- small a, tilde -->
<!ENTITY auml "ä" -- small a, dieresis or umlaut mark -->
<!ENTITY ccedil "ç" -- small c, cedilla -->
<!ENTITY eacute "é" -- small e, acute accent -->
<!ENTITY ecirc "ê" -- small e, circumflex accent -->
<!ENTITY egrave "è" -- small e, grave accent -->
<!ENTITY eth "ð" -- small eth, Icelandic -->
<!ENTITY euml "ë" -- small e, dieresis or umlaut mark -->
<!ENTITY gt ">" -- greater than -->
<!ENTITY iacute "í" -- small i, acute accent -->
<!ENTITY icirc "î" -- small i, circumflex accent -->
<!ENTITY igrave "ì" -- small i, grave accent -->
<!ENTITY iuml "ï" -- small i, dieresis or umlaut mark -->
<!ENTITY lt "<" -- less than -->
<!ENTITY ntilde "ñ" -- small n, tilde -->
<!ENTITY oacute "ó" -- small o, acute accent -->
<!ENTITY ocirc "ô" -- small o, circumflex accent -->
<!ENTITY ograve "ò" -- small o, grave accent -->
<!ENTITY oslash "ø" -- small o, slash -->
<!ENTITY otilde "õ" -- small o, tilde -->
<!ENTITY ouml "ö" -- small o, dieresis or umlaut mark -->
<!ENTITY szlig "ß" -- small sharp s, German (sz ligature) -->
<!ENTITY thorn "þ" -- small thorn, Icelandic -->
<!ENTITY uacute "ú" -- small u, acute accent -->
<!ENTITY ucirc "û" -- small u, circumflex accent -->
<!ENTITY ugrave "ù" -- small u, grave accent -->
<!ENTITY uuml "ü" -- small u, dieresis or umlaut mark -->
<!ENTITY yacute "ý" -- small y, acute accent -->
<!ENTITY yuml "ÿ" -- small y, dieresis or umlaut mark -->
<!-- deprecated elements -->
<!ELEMENT (%literal) - - CDATA>
<!ELEMENT PLAINTEXT - O EMPTY>
<!-- Local Variables: -->
<!-- mode: sgml -->
<!-- compile-command: "sgmls -s -p " -->
<!-- end: -->
]>
Additions to this list will be controlled by the HTML registration authority . Experimental values may be used on the condition that they begin with "X-".
These values of the REL attribute of hypertext links have a significance defined here, and may be treated in special ways by HTML applications.
These relationships relate whole documents (objects), rather than particular anchors within them. If the relationship value is used with a link between anchors rather than whole documents, the semantics are considered to apply to the documents.
In the explanations which follows, A is the source document of the link and B is the destination document specified by the HREF attribute.
A relationship marked "Acyclic" has the property that no sequence of links with that relationship may be followed from any document back to itself. These types of links may therefore be used to define trees.
A document may have any number of index links, causing several indexes top be searched in a client-defined manner.
B must support SEARCH operations under its access protocol.
A document may have any number of glossary links.
Annotation is used by one person to write the equivalent of "margin notes" or other criticism on another's document, for example.
Example: The relationship between a newsgroup and its articles.
Acyclic.
Similar to Annotation, but there is no suggestion that B is subsidiary to A: A and B are on equal footings.
Example: The relationship between a mail message and its reply, a news article and its reply.
Acyclic.
Acyclic.
Acyclic.
Any document may only have one link of this relationship, and/or one link of the reverse relationship.
Note: May be used to control navigational aids, generate printed material, etc. In conjunction with " subdocument ", may be used to define a tree such as a printed book made of hypertext document. The document can only have one such tree.
Acyclic.
A link reverse link must exist from B to A and to all other known versions of A.
Acyclic.
This information can be used for protection, and informing authors of interest, for sending mail to authors, etc.
This information can be used for notification of changes.
Typically, this is a request that, when object B changes in some way, a new link is made to object A.
The phrase "object B changes" may be interpreted narrowly (as "B itself changes") or widely (as "B or anythink linked to it or related to it closely changes"). The amount of change considered worth notifying people about is also subject to interpretation, varying from bit changes in the source to a "new edition" statement by the publisher.
It is proposed that the Internet Assigned Numbers Authority or their successors take this role.
Unregistered values may be used for experimental purposes if they are start with "X-".
Tim Berners-Lee
Address CERN
1211 Geneva 23
Switzerland
Telephone: +41(22)767 3755
Fax: +41(22)767 7155
email: timbl@info.cern.ch
Daniel Connolly
Address: Atrium Technologies, Inc.
5000 Plaza on the Lake, Suite 275
Austin, TX 78746
USA
email: connolly@atrium.com