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Hypertext Markup Language (HTML) Tim Berners-Lee, CERN
Internet Draft Daniel Connolly, Atrium
IIIR Working Group June 1993
Hypertext Markup Language (HTML)
A Representation of Textual Information and MetaInformation
for Retrieval and Interchange
Status of this Document
This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas,
and its Working Groups. Note that other groups may also distribute
working documents as Internet Drafts.
Internet Drafts are working documents valid for a maximum of six
months. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a
"working draft" or "work in progress".
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
Abstract
HyperText Markup Language (HTML) can be used to represent
Hypertext news, mail, online documentation, and collaborative
hypermedia;
Menus of options;
Database query results;
Simple structured documents with inlined graphics.
Hypertext views of existing bodies of information
The World Wide Web (W3) initiative links related information
throughout the globe. HTML provides one simple format for
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RFC XXX Hypertext Markup Language (HTML) June 1993
throughout the globe. HTML provides one simple format for
providing linked information, and all W3 compatible programs are
required to be capable of handling HTML. W3 uses an Internet
protocol (Hypertext Transfer Protocol, HTTP), which allows transfer
representations to be negotiated between client and server, the
result being returned in an extended MIME message. HTML is
therefore just one, but an important one, of the representations
used with W3.
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.
IN THIS DOCUMENT
This document contains the following parts:
Vocabulary used in this document, degrees of imperative.
HTML and MIME with discussion of character sets.
HTML and SGML and the reelationship between them, and
Structured text : an introduction for
beginners to SGML.
HTML Elements A list with description, example, and
typical rendering.
HTML Entities Entities used to describe characters.
The HTML DTD The text of the SGML DTD for HTML
Link relationship values .
A provisional list. Not part of the
standard.
Registration Authority
The authority for extending lists of valid
vales.
References to related documents
Authors addresses Contact information.
tableofcontents
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RFC XXX Hypertext Markup Language (HTML) June 1993
Vocabulary
This specification uses the words below with the precise meaning
given.
Representation The encoding of information for interchange.
For example, HTML is a representation of
hypertext.
Rendering The form of presentation to information to
the human reader.
IMPERATIVES
may The implementation is not obliged to follow
this in any way.
must If this is not followed, the implementation
does not conform to this specification.
shall as "must"
should If this is not followed, though the
implementation officially conforms to the
standard, undesirable results may occur in
practice.
typical Typical rendering is described for many
elements. This is not a mandatory part of the
standard but is given as guidance for
designers and to help explian the uses for
which the elements were intended.
NOTES
Sections marked "Note:" are not mandatory parts of the
specification but for guidance only.
STATUS OF FEATURES
Mainstream All parsers must recognise these features.
Features are mainstream unless otherwise
mentioned.
Extra Standard HTML features which may safely be
ignored by parsers. It is legal to ignore
these, treat the contents as though the tags
were not there. (e.g. EM, and any undefined
elements)
Obsolete Not standard HTML. Parsers should implement
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RFC XXX Hypertext Markup Language (HTML) June 1993
these features as far as poosible in order to
preverve back-compatibility with previous
versions of this specification.
HTML AND MIME
The definition of the HTML content subtype is
MIME Type name text
MIME subtype name: html
Required parameters: none
Optional parameters: charset
Character sets
The base character set (the SGML BASESET) for HTML is ISO Latin-1.
This is the set refered to by any numeric character references. The
actual character set used in the representation of an HTML document
may be ISO Latin 1, or its 7-bit subset which is ASCII. There is
no obligation for an HTML document to contain any characters above
decimal 127. It is possible that a transport medium such as
electronic mail imposes constraints on the number of bits in a
representation of a document, though the HTTP access protocol used
by W3 always allows 8 bit transfer.
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.
INTRODUCTION
The HyperText Markup Language is defined in terms of the ISO
Standard Generalized Markup Language []. SGML is a system for
defining structured document types and markup languages to
represent instances of those document types.
Every SGML document has three parts:
An SGML declaration, which binds SGML processing quantities and
syntax token names to specific values. For example, the SGML
declaration in the HTML DTD specifies that the string that opens
a tag is </ and the maximum length of a name is 40 characters.
A prologue including one or more document type declarations,
which specifiy the element types, element relationships and
attributes, and references that can be represented by markup.
The HTML DTD specifies, for example, that the HEAD element
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RFC XXX Hypertext Markup Language (HTML) June 1993
contains at most one TITLE element.
An instance, which contains the data and markup of the document.
We use the term HTML to mean both the document type and the markup
language for representing instances of that document type.
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.
Structured Text
An HTML instance is like a text file, except that some of the
characters are interpreted as markup. The markup gives structure to
the document.
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>
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RFC XXX Hypertext Markup Language (HTML) June 1993
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.
TAGS
Every element starts with a tag, and every non-empty element ends
with a tag. Start tags are delimited by < and >, and end tags are
delimited by </ and >.
Names
The element name immediately follows the tag open delimiter. Names
consist of a letter followed by up to 33 letters, digits, periods,
or hyphens. Names are not case sensitive.
Attributes
In a start tag, whitespace and attributes are allowed between the
element name and the closing delimiter. An attribute consists of a
name, an equal sign, and a value. Whitespace is allowed around the
equal sign.
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 TYPES
The name of a tag refers to an element type declaration in the HTML
DTD. An element type declaration associates an element name with
A list of attributes and their types and statuses
A content type (one of EMPTY, CDATA, RCDATA, ELEMENT, or MIXED)
which determines the syntax of the element's content
A content model, which specifies the pattern of nested elements
and data
Empty Elements
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RFC XXX Hypertext Markup Language (HTML) June 1993
Empty elements have the keyword EMPTY in their declaration. For
example:
<!ELEMENT NEXTID - O EMPTY>
<!ATTLIST NEXTID N NUMBER #REQUIRED>
This means that the follwing:
<nextid n=''27''>
is legal, but these others are not:
<nextid>
<nextid n=''abc''>
Character Data
The keyword CDATA indicates that the content of an element is
character data. Character data is all the text up to the next end
tag open delimter-in-context. For example:
<!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>
Replaceable Character Data
Elements with RCDATA content behave much like thos with CDATA,
except for character references and entity references. Elements
declared like:
<!ELEMENT TITLE - - RCDATA>
can have any sequence of characters in their content.
Character References
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RFC XXX Hypertext Markup Language (HTML) June 1993
To represent a character that would otherwise be recognized as
markup, use a character referece. The string signals a character
reference when it is followed by a letter or a digit. The delimiter
is followed by the decimal character number and a semicolon. For
example:
<title>You can even represent </end> tags in RCDATA </title>
Entity References
The HTML DTD declares entities for the less than, greater than, and
ampersand characters and each of the ISO Latin 1 characters so that
you can reference them by name rather than by number.
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 mathemetician.
Note: To be sure that a string of characters has
no markup, HTML writers should represent all
occurences of <, >, and & by character or
entity references.
Element Content
Some elements have, in stead of a keyword that states the type of
content, a content model, which tells what patterns of data and
nested elements are allowed. If the content model of an element
does not include the symbol #PCDATA , the content is element
content.
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>
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RFC XXX Hypertext Markup Language (HTML) June 1993
Mixed Content
If the content model includes the symbol #PCDATA, the content of
the element is parsed as mixed content. For example:
<!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''
COMMENTS AND OTHER MARKUP
To include comments in an HTML document that will be ignored by the
parser, surround them with <!-- and -->. After the comment
delimiter, all text up to the next occurence of -- is ignored.
Hence comments cannot be nested. Whitespace is allowed between the
closing -- and >. (But not between the opening <! and --.)
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.
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RFC XXX Hypertext Markup Language (HTML) June 1993
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 >.
LINE BREAKS
A line break character is considered markup (and ignored) if it is
the first or last piece of content in an element. This allows you
to write either
<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 cuz it's the last piece of content:
-->
</pre>
contains only the strings
first line
third line
fourth line.
SPACES AND TABS
Space characters must be rendered as horizontal white space. In
HTML, multiple spaces should be rendered as proportionally larger
spaces.
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RFC XXX Hypertext Markup Language (HTML) June 1993
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.
SUMMARY OF MARKUP SIGNALS
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
HTML ELEMENTS
This is a list of elements used in the HTML language. Documents
should (but need not absolutely) contain an initial HEAD element
followed by a BODY element.
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
Properties of the whole document
Properties of the whole document are defined by the following
elements. They should appear within the HEAD element. Their order
is not significant.
TITLE The title of the document
ISINDEX Sent by a server in a searchable document
NEXTID A parameter used by editors to generate
unique identifiers
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RFC XXX Hypertext Markup Language (HTML) June 1993
LINK Relationship between this document and
another. See also the Anchor element ,
Relationships . A document may have many
LINK elements.
BASE A record of the URL of the document when
saved
Text formatting
These are elements which occur within the BODY element of a
document. Their order is the logical order in which the elements
should be rendered on the output device.
Headings Several levels of heading are supported.
Anchors Sections of text which form the beginning
and/or end of hypertext links are called
"anchors" and defined by the A tag.
Paragraph marks The P element marks the break between two
paragraphs.
Address style An ADDRESS element is displayed in a
particular style.
Blockquote style A block of text quoted from another source.
Lists Bulleted lists, glossaries, etc.
Preformatted text Sections in fixed-width font for
preformatted text.
Character highlighting
Formatting elements which do not cause
paragraph breaks.
Graphics
IMG The IMG tag allows inline graphics.
Obsolete elements
The other elements are obsolete but should be recognised by parsers
for back-compatibility.
HEAD
The HEAD element contains all information about the document in
general. It does not contain any text which is part of the
document: this is in the BODY. Within the head element, only
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RFC XXX Hypertext Markup Language (HTML) June 1993
certain elements are allowed.
BODY
The BODY element contains all the information which is part of the
document, as opposed information about the document which is in the
HEAD .
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 .
Anchors
An anchor is a piece of text which marks the beginning and/or the
end of a hypertext link.
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.
HREF OPTIONAL. If the HREF attribute is present,
the anchor is sensitive text: the start of a
link. If the reader selects this text, (s)he
should be presented with another document
whose network address is defined by the value
of the HREF attribute . The format of the
network address is specified elsewhere . This
allows for the form HREF="#identifier" to
refer to another anchor in the same document.
If the anchor is in another document, the
attribute is a relative name , relative to
the documents address (or specified base
address if any).
NAME OPTIONAL. If present, the attribute NAME
allows the anchor to be the destination of a
link. The value of the attribute is an
identifier for the anchor. Identifiers are
arbitrary strings but must be unique within
the HTML document. Another document can
then make a reference explicitly to this
anchor by putting the identifier after the
address, separated by a hash sign .
REL OPTIONAL. An attribute REL may give the
relationship (s) described by the hypertext
link. The value is a comma-separated list of
relationship values. Values and their
semantics will be registered by the HTML
registration authority. The default
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RFC XXX Hypertext Markup Language (HTML) June 1993
relationship if none other is given is void.
REL should not be present unless HREF is
present. See Relationship values , REV .
REV OPTIONAL. The same as REL , but the
semantics of the link type are in the reverse
direction. A link from A to B with REL="X"
expresses the same relationship as a link
from B to A with REV="X". An anchor may
have both REL and REV attributes.
URN OPTIONAL. If present, this specifies a
uniform resource number for the document. See
note .
TITLE OPTIONAL. This is informational only. If
present the value of this field should equal
the value of the TITLE of the document whose
address is given by the HREF attribute. See
note .
METHODS OPTIONAL. The value of this field is a
string which if present must be a comma
separated list of HTTP METHODS supported by
the object for public use. See note .
All attributes are optional, although one of NAME and HREF is
necessary for the anchor to be useful. See also: LINK .
EXAMPLE OF USE:
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 Organisation may refuse employment to anyone convicted
of a <a href="#serious">serious</A> crime.
NOTE : UNIVERSAL RESOURCE NUMBERS
URNs are provided to allow a document to be recognised if duplicate
copies are found. This should save a client implementation from
picking up a copy of something it already has.
The format of URNs is under discussion (1993) by various working
groups of the Internet Engineering Task Force.
NOTE: TITLE ATTRIBUTE OF LINKS
The link may carry a TITLE attribute which should if present give
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RFC XXX Hypertext Markup Language (HTML) June 1993
the title of the document whose address is given by the HREF
attribute.
This is useful for at least two reasons
The browser software may chose to display the title of the
document as a preliminary to retrieving it, for example as a
margin note or on a small box while the mouse is over the
anchor, or during document fetch.
Some documents -- mainly those which are not marked up text,
such as graphics, plain text and also Gopher menus, do not come
with a title themselves, and so putting a title in the link is
the only way to give them a title. This is how Gopher works.
Obviously it leads to duplication of data, and so it is
dangerous to assume that the title attribute of the link is a
valid and unique title for the destination document.
NOTE: METHODS ATTRIBUTE OF LINKS
The METHODS attributes of anchors and links are used to provide
information about the functions which the user may perform on an
object. These are more accurately given by the HTTP protocol when
it is used, but it may, for similar reasons as for the TITLE
attribute, be useful to include the information in advance in the
link.
For example, The browser may chose a different rendering as a
function of the methods allowed (for example something which is
searchable may get a different icon)
Address
This element is for address information, signatures, authorship,
etc, often at the top or bottom of a document.
TYPICAL RENDERING
Typically, an address element is italic and/or right justified or
indented. The address element implies a paragraph break. Paragraph
marks within the address element do not cause extra white space to
be inserted.
EXAMPLES OF USE:
<ADDRESS><A HREF="Author.html">A.N.Other</A></ADDRESS>
<ADDRESS>
Newsletter editor<p>
J.R. Brown<p>
JimquickPost News, Jumquick, CT 01234<p>
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RFC XXX Hypertext Markup Language (HTML) June 1993
Tel (123) 456 7890
</ADDRESS>
BASE
This element allows the URL of the document itself to be recorded
in situations in which the document may be read out of context.
URLs within the document may be in a "partial" form relative to
this base 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:
HREF the URL
BLOCKQUOTE
The BLOCKQUOTE element allows text quoted from another source to be
rendered specially.
TYPICAL RENDERING
A typical rendering might be a slight extra left and right indent,
and/or italic font. BLOCKQUOTE causes a paragraph break, and
typically a line or so of white space will be allowed between it
and any text before or after it.
Single-font rendition may for example put a vertical line of ">"
characters down the left margin to indicate quotation in the
Internet mail style.
EXAMPLE
I think it ends
<BLOCKQUOTE>Soft you now, the fair Ophelia. Nymph, in thy orisons,
be all my sins remembered.
</BLOCKQUOTE>
but I am not sure.
Headings
Six levels of heading are supported. (Note that a hypertext node
within a hypertext work tends to need less levels of heading than
a work whose only structure is given by the nesting of headings.)
A heading element implies all the font changes, paragraph breaks
before and after, and white space (for example) necessary to render
the heading. Futher character emphasis or paragraph marks are not
required in HTML.
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RFC XXX Hypertext Markup Language (HTML) June 1993
H1 is the highest level of heading, and is recommened 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 prodcue
strange results for example when generating other representations
from the HTML.
EXAMPLE:
<H1>This is a heading</H1>
Here is some text
<H2>Second level heading</H2>
Here is some more text.
PARSER NOTE:
Parsers should not require any specific order to heading elements,
even if the heading level increases by more than one between
successive headings.
TYPICAL RENDERING
H1 Bold very large font, centered. One or two
lines clear space between this and anything
following. If printed on paper, start new
page.
H2 Bold, large font,, flush left against left
margin, no indent. One or two clear lines
above and below.
H3 Italic, large font, slightly indented from
the left margin. One or two clear lines above
and below.
H4 Bold, normal font, indented more than H3.
One clear line above and below.
H5 Italic, normal font, indented as H4. One
clear line above.
H6 Bold, indented same as normal text, more
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RFC XXX Hypertext Markup Language (HTML) June 1993
than H5. One clear line above.
These typical values are just an indication, and it is up to the
designer of the presentation software to define the styles. The
reader may have options to customise these. When writing
documents, you should assume that whatever is done it is designed
to have the same sort of effect as the styles above.
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.
IMG: Embedded Images
Status: Extra
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 two
attributes:
SRC The value of this attribute is the URL of
the document to be embedded. Its syntax is
the same as that of the HREF attribute of the
A tag. SRC is mandatory.
ALIGN Take values TOP or MIDDLE or BOTTOM,
defining whether the tops or middles of
bottoms of the graphics and text should be
aligned vertically.
Note that IMG elements are allowed within anchors.
EXAMPLE
Warning: < IMG SRC ="triangle.gif"> This must be done by a
qualified technician.
< A HREF="Go">< IMG SRC ="Button"> Press to start</A>
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RFC XXX Hypertext Markup Language (HTML) June 1993
ISINDEX
This element informs the reader that the document is an index
document. As well as reading it, the reader may use a keyword
search.
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.
EXAMPLE OF USE:
<ISINDEX>
LINK
The LINK element occurs within the HEAD element of an HTML
document. It is used to indicate a relationship between the
document and some other object. A document may have any number of
LINK elements.
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.
Forms of list in HTML
GLOSSARIES
A glossary (or definition list) is a list of paragraphs each of
which has a short title alongside it. Apart from glossaries, this
element is useful for presenting a set of named elements to the
reader. The elements within a glossary follow are
DT The "term", typically placed in a wide left
indent
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RFC XXX Hypertext Markup Language (HTML) June 1993
DD The "definition", which may wrap onto many
lines
These elements must appear in pairs. Single occurences of DT
without a following DD are illegal. The one attribute which DL can
take is
COMPACT suggests that a compact rendering be used,
because the enclosed elements are
individually small, or the whole glossary is
rather large, or both.
Typical rendering
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 acrosss 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.
Examples of use
<DL>
<DT>Term the first<DD>definition paragraph is reasonably
long but is still diplayed clearly
<DT>Term2 follows<DD>Definition of term2
</DL>
<DL COMPACT>
<DT>Term<DD>definition pagagraph
<DT>Term2<DD>Definition of term2
</DL>
LISTS
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RFC XXX Hypertext Markup Language (HTML) June 1993
A list is a sequence of paragraphs, each of which may be preceded
by a special mark or sequence number. The syntax is:
<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.
Typical rendering
The representation of the list is not defined here, but a bulleted
list for unordered lists, and a sequence of numbered paragraphs
for an ordered list would be quite appropriate. Other possibilities
for interactive display include embedded scrollable browse panels.
List elements with typical rendering are:
UL A list of multi-line paragraphs, typically
separated by some white space and/or marked
by bullets, etc.
OL As UL, but the paragraphs are typically
numbered in some way to indicate the order as
significant.
MENU A list of smaller paragraphs. Typically one
line per item, with a style more compact than
UL.
DIR A list of short elements, typically less
than 20 characters. These may be arranged in
columns across the page, typically 24
character in width. If the rendering software
is able to optimise the column width as
function of the widths of individual
elements, so much the better.
Example of use
<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 >
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RFC XXX Hypertext Markup Language (HTML) June 1993
<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>
Next ID
This tag takes a single attribute which is the number of the next
document-wide numeric identifier to be allocated of the form z123.
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.
EXAMPLE OF USE:
<NEXTID N=27>
P: Paragraph mark
The empty P element indicates a paragraph break. The exact
rendering of this (indentation, leading, etc) is not defined here,
and may be a function of other tags, style sheets etc.
<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 responsability 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.
TYPICAL RENDERING
Typically, <P> will generate a small vertical space (of a line or
half a line) between the paragraphs. This is not the case
(typically) within ADDRESS or (ever) within PRE elements. With
some implementations, in normal text, <P> may generate a small
extra left indent on the first line.
EXAMPLES OF USE
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RFC XXX Hypertext Markup Language (HTML) June 1993
<h1>What to do</h1>
This is a one paragraph.< p >This is a second.
< P >
This is a third.
BAD EXAMPLE
<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.
PRE: Preformatted text
Preformatted elements in HTML are displayed with text in a fixed
width font, and so are suitable for text which has been formatted
for a teletype by some existing formatting system.
The optional attribute is:
WIDTH This attribute gives the maximum number of
characters which will occur on a line. It
allows the presentation system to select a
suitable font and indentation. Where the
WIDTH attribute is not recognised, it is
recommened that a width of 80 be assumed.
Where WIDTH is supported, it is recommeded
that at least widths of 40, 80 and 132
characters be presented optimally, with other
widths being rounded up.
Within a PRE element,
Line boundaries within the text are rendered as a move to the
beginning of the next line, except for one immediately following
or immediately preceding a tag.
The <p> tag should not be used. If found, it should be rendered
as a move to the beginning of the next line.
Anchor elements and character highlighting elements may be used.
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RFC XXX Hypertext Markup Language (HTML) June 1993
Elements which define paragraph formatting (Headings, Address,
etc) must not be used.
The ASCII Horizontal Tab (HT) character must be interpreted as
the smallest positive nonzero number of spaces which will leave
the number of characters so far on the line as a multiple of 8.
Its use is not recommended however.
Example of use
<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.
TITLE
The title of a document is specified by the TITLE element. The
TITLE element should occur in the HEAD of the document.
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.
Examples of use
Appropriate titles might be
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RFC XXX Hypertext Markup Language (HTML) June 1993
<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>
Character highlighting
Status: Extra
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>emphasised</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
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RFC XXX Hypertext Markup Language (HTML) June 1993
alternative, or the default, style, with some loss of qualtity 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.
PHYSICAL STYLES
TT Fixed-width typewriter font.
B Boldface, where available, otherwise
alternative mapping allowed.
I Italic font (or slanted if italic
unavailable).
U Underline.
LOGICAL STYLES
EM Emphasis, typically italic.
STRONG Stronger emphasis, typically bold.
CODE Example of code. typically monospaced font.
(Donot confuse with PRE)
SAMP A sequence of litteral characters.
KBD in an instruction manual, Text typed by a
user.
VAR A variable name.
DFN The defining instance of a term. Typically
bold or bold italic.
CITE A citation. Typically italic.
EXAMPLES OF USE
This text contains an <em>emphasised</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.
Obsolete elements
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RFC XXX Hypertext Markup Language (HTML) June 1993
The following elements of HTML are obsolete. It is recommended
that client implementors implement the obsolete forms for
compatibility with old servers.
Plaintext
Status: Obsolete .
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
t
This tag allows the rest of a file to be read efficiently without
parsing. Its presence is an optimisation. There is no closing tag.
The rest of the data is not in SGML.
XMP and LISTING: Example sections
Status: Obsolete . This are in use and should be recognised by
browers. New servers should use <PRE> instead.
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:
The text may contain any ISO Latin printable characters, but not
the end tag opener. (See Historical note )
Line boundaries are significant, except any occuring immediately
after the opening tag or before the closing tag. and are to be
rendered as a move to the start of a new line.
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RFC XXX Hypertext Markup Language (HTML) June 1993
The ASCII Horizontal Tab (HT) character must be interpreted as
the smallest positive nonzero number of spaces which will leave
the number of characters so far on the line as a multiple of 8.
Its use is not recommended however.
The LISTING element is portrayed so that at least 132 characters
will fit on a line. The XMP elemnt is portrayed in a font so that
at least 80 characters will fit on a line but is otherwise
identical to LISTING.
Highlighted Phrase HP1 etc
Status: Obsolete . These tags like all others should be ignored if
not implemented. Replaced will more meaningful elements -- see
character highlighting .
Examples of use:
<HP1>...</HP1> <HP2>... </HP2> etc.
Comment element
Status: Obsolete
A comment element used for bracketing off unneed text and comment
has been intriduced in some browsers but will be replaced by the
SGML command feature in new implementations.
HISTORICAL NOTE: XMP AND LISTING
The XMP and LISTING elements used historically to have non SGML
conforming specifications, in that the text could contain any ISO
Latin printable characters, including the tag opener, so long as it
does not contain the closing tag in full.
This form is not supported by SGML and so is not the specified HTML
interpretation. Providers should be warned that implemntations may
vary on how they interpret end tags apparently within these
elements
ENTITIES
The following entity names are used in HTML , always prefixed by
ampersand (&) and followed by a semicolon as shown. They represent
particular graphic characters which have special meanings in places
in the markup, or may not be part of the character set available to
the writer.
< The less than sign <
> The "greater than" sign >
& The ampersand sign & itself.
Berners-Lee and Connolly 28
RFC XXX Hypertext Markup Language (HTML) June 1993
" The double quote sign "
Also allowed are references to any of the ISO Latin-1 alphabet,
using the entity names in the following table.
ISO Latin 1 character entities
This list is derived from "ISO 8879:1986//ENTITIES Added Latin
1//EN".
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
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RFC XXX Hypertext Markup Language (HTML) June 1993
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
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RFC XXX Hypertext Markup Language (HTML) June 1993
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
THE HTML DTD
The HTML DTD follows . Its relationship to the content of an SGML
document is explained in the section "HTML and SGML" .
<!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 understaning 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
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RFC XXX Hypertext Markup Language (HTML) June 1993
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
Berners-Lee and Connolly 32
RFC XXX Hypertext Markup Language (HTML) June 1993
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 relashionship type --
REV CDATA #IMPLIED -- reverse relashionship type
to referent data:
PARENT CHILD, SIBLING, NEXT, TOP,
Berners-Lee and Connolly 33
RFC XXX Hypertext Markup Language (HTML) June 1993
DEFINITION, UPDATE, ORIGINAL etc. --
URN CDATA #IMPLIED -- universal resource number --
TITLE CDATA #IMPLIED -- advisory only --
METHODS NAMES #IMPLIED -- supported public methods of the obje
ct:
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 t
ext.
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 o
n
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 "
>
Berners-Lee and Connolly 34
<!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
Berners-Lee and Connolly 35
RFC XXX Hypertext Markup Language (HTML) June 1993
>
<!-- 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 -->
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RFC XXX Hypertext Markup Language (HTML) June 1993
<!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: -->
]>
LINK RELATIONSHIP VALUES
Status: This list is not part of the standard. It is intended to
illustrate the use of link relationships and to provide a framework
for further development.
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.
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RFC XXX Hypertext Markup Language (HTML) June 1993
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.
Relationships between documents
These relationships are between the documents themselves rather
than the subjects of the documents.
USEINDEX
B is a related index for a search by a user reading this document
who asks for an index search function.
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.
USEGLOSSARY
B is an index which should be used to resolve glossary queries in
the document. (Typically, a double-click on a word which is not
within an anchor).
A document may have any number of glossary links.
ANNOTATION
The information in B is additional to and subsidiary to that in A.
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.
REPLY
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.
EMBED
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RFC XXX Hypertext Markup Language (HTML) June 1993
If this link is followed, the node at the end of it is embedded
into the display of the source document.
Acyclic.
PRECEDES
In an ordered structure defined by the author, A precedes B, B is
followed by A.
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.
SUBDOCUMENT
B is a lower part in the author's hierarchy to A. Acyclic. See
also Precedes.
PRESENT
Whenever A is presented, B must also be presented. This implies
that whenever A is retrieved, B must also be retrieved.
SEARCH
When the link is followed, the node B should be searched rather
than presented. That is, where the client software allows it, the
user should immediately be presented with a search panel and
prompted for text. The search is then performed without an
intermediate retrieval or presentation of the node B
SUPERSEDES
B is a previous version of A.
Acyclic.
HISTORY
B is a list of versions of A
A link reverse link must exist from B to A and to all other known
versions of A.
Relationships about subjects of documents
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RFC XXX Hypertext Markup Language (HTML) June 1993
These relationships convey semantics about objects described by
documents, rather than the documents themselves.
INCLUDES
A includes B, B is part of A. For example, a person described by
document A is a part of the group described by document B.
Acyclic.
MADE
Person (etc) described by node A is author of, or is responsible
for B
This information can be used for protection, and informing authors
of interest, for sending mail to authors, etc.
INTERESTED
Person (etc) described by A is interested in node B
This information can be used for informing readers of changes.
REGISTRATION AUTHORITY
The HTTP Registration Authority is responsible for maintaining
lists of:
Relationship names for link and anchor elements
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-".
REFERENCES
SGML ISO 8879:1986, Information ProcessingText
and Office SystemsStandard Generalized Markup
Language (SGML).
sgmls an SGML parser by James Clark
<jjc@jclark.com> derived from the ARCSGML
parser materials which were written by
Charles F. Goldfarb. The source is available
on the ifi.uio.no FTP server in the directory
/pub/SGML/SGMLS .
WWW The World-Wide Web , a global information
initiative. For boostrap information, telnet
info.cern.ch or find documents by
Berners-Lee and Connolly 40
RFC XXX Hypertext Markup Language (HTML) June 1993
ftp://info.cern.ch/pub/www/doc
URL Universal Resource Locators. RFCxxx.
Currently available by anonymous FTP from
info.cern.ch in /pub/ietf.
AUTHOR'S ADDRESSES
This document was prepared with the help and advice of many people
across the net. Dan Connolly prepared the DTD and the section on
HTML and SGML whilst with Convex Computer Corporation of 3000
Waterview Parkway Richardson, TX 75083. He is now with Atrium
Technology Inc., and is not a current editor of the document.
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
Berners-Lee and Connolly 41