\documentstyle[rfc,fancyheadings,times]{cernman}
\lhead[RFC XXX]{June 1993}
\chead{Hypertext Markup language}
\rhead[June 1993]{RFC XXXX}
\lfoot[\thepage]{Berners-Lee and Connolly}
\rfoot[Berners-Lee and Connolly]{\thepage}
\cfoot{}
\pagestyle{fancy}
\begin{document}
% First page special
\thispagestyle{plain}
\begin{tabular*}{\textwidth}{@{}l@{\extracolsep{\fill}}r@{}}
Hypertext Markup Language&Tim Berners-Lee, CERN\\
Internet Draft&Daniel Connolly, Atrium Technology Inc.\\
IIIR Working Group&June 1993\\[0.5cm]
\end{tabular*}

\begin{center}
\Large\bf\sf
Hypertext Markup Language\\[1cm]
\large A Representation of Textual Information and Metainformation\\
for Retrieval and Interchange\\[1cm]
\end{center}
% --------------------------------------------------------





\section*{Status of this Document}This document is an Internet Draft.
Internet Draft. 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.\par 
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".\par 
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.\par 
This is version 1.1 of this specification.
This document is available in hypertext
on the World-Wide Web as http://info.cern.ch/hypertext/WWW/MarkUp/HTML.html
\section*{Abstract}HyperText Markup Language (HTML)
 can be used to represent
\begin{itemize}
\item Hypertext news, mail, online documentation,
and collaborative hypermedia;
\item Menus of  options;
\item Database query results;
\item Simple structured documents with
inlined graphics.
\item Hypertext views of existing bodies
of information
\end{itemize}The World Wide Web (W3) initiative
links related information 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.
\par 
HTML is proposed as a  MIME content
type.\par 
HTML refers to the URL specification
of RFCxxxx.\par 
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 \lbrack SGMLS\rbrack  .  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.
\chapter{In this document}This document contains the following
parts:
\begin{DL}{allow this much space}
\item[Vocabulary 
]used in this document,
degrees of imperative.
\item[HTML and MIME 
]with discussion of
character sets.
\item[HTML and SGML 
]and the reelationship
between them,  and Structured text
: an introduction for beginners to
SGML.
\item[HTML Elements
] A list with description,
example, and typical rendering.
\item[HTML Entities
] Entities used to describe
characters.
\item[The HTML DTD
] The text of the SGML
DTD for HTML
\item[Link relationship values .
] A provisional
list. Not part of the standard.
\item[Registration Authority
] The authority
for extending lists of valid vales.
\item[References
] to related documents
\item[Authors addresses
] Contact information.
\end{DL}
\tableofcontents





\section{Vocabulary}This specification uses the words
below with the precise meaning given.
\begin{DL}{allow this much space}
\item[Representation
] The encoding of information
for interchange. For example, HTML
is a representation of hypertext.
\item[Rendering
] The form of presentation
to information to the human reader.
\end{DL}

\subsection{Imperatives}
\begin{DL}{allow this much space}
\item[may
] The implementation is not obliged
to follow this in  any way.
\item[must
] If this is not followed, the
implementation does not conform to
this specification.
\item[shall
] as "must"
\item[should
] If this is not followed, though
the implementation officially conforms
to the standard, undesirable results
may occur in practice.
\item[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.
\end{DL}

\subsection{Notes}Sections marked "Note:" are not mandatory
parts of the specification but for
guidance only.
\subsection{Status of features}
\begin{DL}{allow this much space}
\item[Mainstream
] All parsers must recognise
these features.  Features are mainstream
unless otherwise mentioned.
\item[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)
\item[Obsolete
] Not standard HTML.  Parsers
should implement these features as
far as poosible in order to preverve
back-compatibility with oprevious
versions of this specification.
\end{DL}





\chapter{HTML and MIME}The definition of the HTML content
subtype is
\begin{DL}{allow this much space}
\item[MIME Type name
] text
\item[MIME subtype name:
] html
\item[Required parameters:
] none
\item[Optional parameters:
] charset
\end{DL}

\section{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.\par 
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.



\chapter{HTML and SGML}The HyperText Markup Language is
defined in terms of the ISO Standard
Generalized Markup Language \lbrack SGML\rbrack .
SGML is a system for defining structured
document types and markup languages
to represent instances of those document
types.\par 
Every SGML document has three parts:\par 
 
\begin{itemize}
\item 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 60;/ and the
maximum length of a name is 40 characters.

\item 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
contains at most one TITLE element.
\item An instance, which contains the data
and markup of the document.
\end{itemize}We use the term HTML to mean both
the document type and the markup
language for representing instances
of that document type.\par 
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.\par 
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.\par 






\section{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.\par 
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: 
\begin{verbatim}		<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>

\end{verbatim}
Some elements (e.g. P, LI) are empty.
They have no content. They show up
as just a start tag. \par 
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.
\subsection{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 $>$. 
\subsubsection{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.
\subsubsection{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.\par 
The value is specified in a string
surrounded by single quotes or a
string surrounded by double quotes.
(See: other tolerated forms @@)\par 
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.\par 
The length of an attribute value
(after parsing) is limited to 1024
characters. 
\subsection{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
\begin{itemize}
\item A list of attributes and their types
and statuses
\item A content type (one of EMPTY, CDATA,
RCDATA, ELEMENT, or MIXED) which
determines the syntax of the element's
content
\item A content model, which specifies
the pattern of nested elements and
data
\end{itemize}
\subsubsection{Empty Elements}Empty elements have the keyword EMPTY
in their declaration. For example:
\begin{verbatim}	<!ELEMENT NEXTID - O EMPTY>
	<!ATTLIST NEXTID N NUMBER #REQUIRED>

\end{verbatim}
This means that the follwing:
\begin{verbatim}	<nextid n=''27''>

\end{verbatim}
is legal, but these others are not:
\begin{verbatim}	<nextid>
	<nextid n=''abc''>

\end{verbatim}

\subsubsection{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:
\begin{verbatim}<!ELEMENT XMP - - CDATA>
\end{verbatim}
specifies that the following text
is a legal XMP element:
\begin{verbatim}	<xmp>Here's an example. It looks like it has
	<tags> and <!--comments-->
	in it, but it does not. Even this
	</ is data.</xmp>

\end{verbatim}
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:
\begin{verbatim}	<xmp>There is no way to represent </end> tags
	in CDATA </xmp>

\end{verbatim}

\subsubsection{Replaceable Character Data}Elements with RCDATA content behave
much like thos with CDATA, except
for character references and entity
references. Elements declared like:
\begin{verbatim}<!ELEMENT TITLE - - RCDATA>
\end{verbatim}
can have any sequence of characters
in their content.
\paragraph{Character References}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:
\begin{verbatim}<title>You can even represent &#60;/end> tags in RCDATA </title>

\end{verbatim}

\paragraph{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.\par 
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:
\begin{verbatim}Kurt G&ouml;del was a famous logician and mathemetician.

\end{verbatim}

\begin{DL}{allow this much space}
\item[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.
\end{DL}

\subsubsection{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. \par 
Whitespace in element content is
considered markup and ignored. Any
characters that are not markup, that
is, data characters, are illegal.\par 
For example:
\begin{verbatim}<!ELEMENT HEAD - - (TITLE? & ISINDEX? & NEXTID? & LINK*)>
\end{verbatim}
declares an element that may be used
as follows:
\begin{verbatim}<head>
 <isindex>
 <title>Head Example</title>
</head>
\end{verbatim}
But the following are illegal:
\begin{verbatim}<head> no data allowed! </head>
<head><isindex><title>Two isindex tags</title><isindex></head>
\end{verbatim}

\subsubsection{Mixed Content}If the content model includes the
symbol \#PCDATA, the content of the
element is parsed as mixed content.
For example:
\begin{verbatim}<!ELEMENT PRE - - (#PCDATA | A | B | I | U | P)+>
<!ATTLIST PRE
	WIDTH NUMBER #implied
	>
\end{verbatim}
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:
\begin{verbatim}<pre>
<b>NAME</b>
    cat -- concatenate<a href=''terms.html#file''>files</a>
<b>EXAMPLE</b>
    cat <xyz
</pre>
\end{verbatim}
The content of the above PRE element
is:
\begin{itemize}
\item A B element
\item The string ``   cat $--$ concatenate''
\item An A element
\item The string ``\char'134 n''
\item Another B element
\item The string ``\char'134 n   cat $<$xyz''
\end{itemize}
\subsection{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 $--$.)\par 
For example:
\begin{verbatim}<HEAD>
<TITLE>HTML Guide: Recommended Usage</TITLE>
<!-- $Id: recommended.html,v 1.3 93/01/06 18:38:11 connolly Exp $ -->
</HEAD>
 
\end{verbatim}
There are a few other SGML markup
constructs that are deprecated or
illegal.
\begin{DL}{allow this much space}
\item[Delimiter
] Signals...
\item[$<$?
] Processing instruction. Terminated
by $>$. 
\item[$<$!\lbrack 
] Marked section. Marked sections
are deprecated. See the SGML standard
for complete information.
\item[$<$!
] Markup declaration. HTML defines
no short reference maps, so these
are errors. Terminated by $>$.
\end{DL}

\subsection{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
\begin{verbatim}<PRE>some example text</pre>
\end{verbatim}
or
\begin{verbatim}<pre>
some example text
</pre>
\end{verbatim}
and these will be processed identically.\par 
Also, a line that's not empty but
contains no content will be ignored
altogether. For example, the element
\begin{verbatim}<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>
\end{verbatim}
contains only the strings
\begin{verbatim}
 first line

 third line
 fourth line.

\end{verbatim}

\subsection{Spaces and Tabs}Space characters must be rendered
as horizontal white space.  In HTML,
multiple spaces should be rendered
as proportionally larger spaces.\par 
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.\par 
Neither spaces nor tabs should be
used to make SGML source layout more
attractive or easier to read.
\subsection{Summary of Markup Signals}The following delimiters may signal
markup, depending on context.
\begin{DL}{allow this much space}
\item[Delimiter
] Signals
\item[$<$!$--$
] Comment
\item[\&\#
] Character reference
\item[\&
] Entity reference
\item[$<$/
] End tag
\item[$<$!
] Markup declaration
\item[\rbrack \rbrack $>$
] Marked section close (an error)
\item[$<$
] Start tag
\end{DL}






\chapter{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. \par 
 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.\par 
See also:  Status of elements
\section{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.
\begin{DL}{allow this much space}
\item[TITLE
] The title of the document
\item[ISINDEX
] Sent by a server in a searchable
document
\item[NEXTID
] A parameter used by editors
to generate unique identifiers
\item[LINK
] Relationship between this document
and another. See also the Anchor
element , Relationships .  A document
may have many LINK elements.
\item[BASE
] A record of the URL of the document
when saved
\end{DL}

\section{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.
\begin{DL}{allow this much space}
\item[Headings
] Several levels of heading
are supported.
\item[Anchors
] Sections of text which form
the beginning and/or end of hypertext
links are called "anchors" and defined
by the A tag.
\item[Paragraph marks
] The P element marks
the break between two paragraphs.
\item[Address style
] An ADDRESS element
is displayed in a particular style.
\item[Blockquote style
] A block of text
quoted from another source.
\item[Lists
] Bulleted lists, glossaries,
etc.
\item[Preformatted text
] Sections in fixed-width
font for preformatted text.
\item[Character highlighting
] Formatting
elements which do not cause paragraph
breaks.
\end{DL}

\section{Graphics}
\begin{DL}{allow this much space}
\item[IMG
] The IMG tag allows inline graphics.
\end{DL}

\section{Obsolete elements}The other elements are obsolete but
should be recognised by parsers for
back-compatibility.





\section{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 certain elements are allowed.







\section{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 .\par 
The elements within the BODY element
are in the order in which they should
be presented to the reader.\par 
See the list of things which are
allowed within a BODY element .





\section{Anchors}An anchor is a piece of text which
marks the beginning and/or the end
of a hypertext link.   \par 
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.
\begin{DL}{allow this much space}
\item[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).
\item[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 .
\item[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 relationship
if none other is given is void. REL
should not be present unless HREF
is present. See Relationship values
, REV .
\item[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.
\item[URN
] OPTIONAL. If present, this specifies
a uniform resource number for the
document. See note .
\item[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 . 
\item[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 .
\end{DL}
All attributes are optional, although
one of NAME and HREF is necessary
for the anchor to be useful. See
also: LINK .
\subsection{Example of use:}
\begin{verbatim}	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.

\end{verbatim}






\subsection{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.\par 
The format of URNs is under discussion
(1993) by various working groups
of the Internet Engineering Task
Force.







\subsection{Note:  TITLE attribute of links}The link may carry a TITLE attribute
which should if present give the
title of the document whose address
is given by the HREF attribute.\par 
This is useful for at least two reasons
\begin{itemize}
\item 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.
\item 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.
\end{itemize}





\subsection{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.\par 
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)






\section{Address}This element is for address information,
signatures, authorship, etc, often
at the top or bottom of a document.
\subsection{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.
\subsection{Examples of use:}
\begin{verbatim}		<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>


\end{verbatim}






\section{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.\par 
Where the base address is not specified,
the reader will use the URL it used
to access the document to resolve
any relative URLs.\par 
The one attribute is:
\begin{DL}{allow this much space}
\item[HREF
] the URL
\end{DL}






\section{BLOCKQUOTE}The BLOCKQUOTE element allows text
quoted from another source to be
rendered specially.
\subsection{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.\par 
Single-font rendition may for example
put a vertical line of "$>$" characters
down the left margin to indicate
quotation in the Internet mail style.
\subsection{Example}
\begin{verbatim}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.
\end{verbatim}





\section{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.)\par 
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.\par 
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.\par 
The heading elements are
\begin{verbatim}		<H1>, <H2>, <H3>, <H4>, <H5>, <H6>

\end{verbatim}
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.
\subsection{Example:}
\begin{verbatim}		<H1>This is a heading</H1>
		Here is some text
		<H2>Second level heading</H2>
		Here is some more text.

\end{verbatim}

\subsection{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.
\subsection{Typical Rendering}
\begin{DL}{allow this much space}
\item[H1
] Bold very large font, centered.
One or two lines clear space between
this and anything following.  If
printed on paper, start new page.
\item[H2
] Bold, large font,, flush left
against left margin, no indent. One
or two clear lines above and below.
\item[H3
] Italic, large font, slightly indented
from the left margin. One or two
clear lines above and below.
\item[H4
] Bold, normal font, indented more
than H3. One clear line above and
below.
\item[H5
] Italic, normal font, indented
as H4.  One clear line above.
\item[H6
] Bold, indented same as normal
text, more than H5. One clear line
above.
\end{DL}
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.\par 
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.\par 






\section{IMG: Embedded Images}Status: Extra\par 
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.\par 
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.\par 
The IMG element is empty: it has
no closing tag. It has two attributes:
\begin{DL}{allow this much space}
\item[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.
\item[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.
\end{DL}
Note that IMG elements are allowed
within anchors.
\subsection{Example}
\begin{verbatim}	Warning: < IMG SRC ="triangle.gif"> This must be done by a
	qualified technician.

	< A HREF="Go">< IMG SRC ="Button"> Press to start</A>




\end{verbatim}






\section{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.\par 
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
.\par 
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!\par 
Status: standard.
\subsection{Example of use:}
\begin{verbatim}		<ISINDEX>

\end{verbatim}





\section{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. \par 
The LINK element is empty, but takes
the same attributes as the anchor
element .\par 
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.\par 
Servers may also allow links to be
added by those who do not have the
right to alter the body of a document.





\section{Forms of list in HTML}
\subsection{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
\begin{DL}{allow this much space}
\item[DT
] The "term", typically placed in
a wide left indent
\item[DD
] The "definition", which may wrap
onto many lines
\end{DL}
These elements must appear in pairs.
Single occurences of DT without a
following DD are illegal.  The one
attribute which DL can take is
\begin{DL}{allow this much space}
\item[COMPACT
] suggests that a compact rendering
be used, because the enclosed elements
are individually small, or the whole
glossary is rather large, or both.
\end{DL}

\subsubsection{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.\par 
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.\par 
The COMPACT attribute may also reduce
the width of the left-hand (DT) column.
\subsubsection{Examples of use}
\begin{verbatim}	<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>




\end{verbatim}

\subsection{Lists}A list is a sequence of paragraphs,
each of which may be preceded by
a special mark or sequence number.
The syntax is:
\begin{verbatim}
		<UL>
		<LI> list element
		<LI> another list element ...
		</UL>

\end{verbatim}
The opening list tag  may be any
of UL, OL, MENU or DIR.  It must
be immediately followed by the first
list element. 
\subsubsection{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.\par 
List elements with typical rendering
are:
\begin{DL}{allow this much space}
\item[UL
] A list of multi-line paragraphs,
typically separated by some white
space and/or marked by bullets, etc.
\item[OL
] As UL, but the paragraphs are
typically numbered in some way to
indicate the order as significant.
\item[MENU
] A list of smaller paragraphs.
Typically one line per item, with
a style more compact than UL.
\item[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.
\end{DL}

\subsubsection{Example of use}
\begin{verbatim}		<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>


\end{verbatim}






\section{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. \par 
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. 
\subsection{Example of use:}
\begin{verbatim}		<NEXTID N=27>


\end{verbatim}






\section{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.\par 
$<$P$>$ is used between two pieces of
text which otherwise would be flowed
together.\par 
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.
\subsection{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.
\subsection{Examples of use}
\begin{verbatim}	<h1>What to do</h1>
	This is a one paragraph.< p >This is a second.
	< P >
	This is a third.

\end{verbatim}

\subsection{Bad example}
\begin{verbatim}        <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.



\end{verbatim}






\section{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.

\begin{verbatim}

\end{verbatim}
The optional attribute is:
\begin{DL}{allow this much space}
\item[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.
\end{DL}
Within a PRE element,
\begin{itemize}
\item 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.
\item  The $<$p$>$ tag should not be used.
If found, it should be rendered as
a move to the beginning of the next
line.
\item Anchor elements and character highlighting
elements may be used.
\item Elements which define paragraph formatting
(Headings, Address, etc) must not
be used.
\item 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.
\end{itemize}
\subsubsection{Example of use}
\begin{verbatim}			<PRE WIDTH="80">
			This is an example line
			</PRE>

\end{verbatim}

\subsubsection{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.
\subsubsection{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.





\section{TITLE}The title of a document is specified
by the TITLE element.  The TITLE
element should occur in the HEAD
of the document.\par 
There may only be one title in any
document. It should identify the
content of the document in a fairly
wide context.\par 
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.
\subsubsection{Examples of use}Appropriate titles might be
\begin{verbatim}		<TITLE>Rivest and Neuman. 1989(b)</TITLE>
\end{verbatim}
or
\begin{verbatim}		<TITLE>A Recipe for Maple Syrup Flap-Jack</TITLE>

\end{verbatim}
or
\begin{verbatim}		<TITLE>Introduction -- AFS user's Guide</TITLE>

\end{verbatim}
Examples of inappropriate titles
are those which are only meaningful
within context,
\begin{verbatim}		<TITLE>Introduction</TITLE>

\end{verbatim}
or too long,
\begin{verbatim}	<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>




\end{verbatim}






\section{Character highlighting}Status: Extra\par 
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.\par 
Where not supported by implementations,
like all tags, these tags should
be ignored but the content rendered.\par 
All these tags have related closing
tags, as in
\begin{verbatim}		This is <EM>emphasised</EM> text.

\end{verbatim}
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".)
\subsubsection{Note:}Browsers unable to display a specified
style may render it in some 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.\par 
These element names are derived from
TeXInfo macro names.
\subsection{Physical styles}
\begin{DL}{allow this much space}
\item[TT
] Fixed-width typewriter font.
\item[B
] Boldface, where available, otherwise
alternative mapping allowed.
\item[I
] Italic font (or slanted if italic
unavailable).
\item[U
] Underline.
\end{DL}

\subsection{Logical styles}
\begin{DL}{allow this much space}
\item[EM
] Emphasis, typically italic.
\item[STRONG
] Stronger emphasis, typically
bold.
\item[CODE
] Example of code. typically monospaced
font. (Donot confuse with  PRE)
\item[SAMP
] A sequence of litteral characters.
\item[KBD
] in an instruction manual, Text
typed by a user.
\item[VAR
] A variable name.
\item[DFN
] The defining instance of a term.
 Typically bold or bold italic.
\item[CITE
] A citation. Typically italic.
\end{DL}

\subsection{Examples of use}
\begin{verbatim}	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.



\end{verbatim}






\section{Obsolete elements}The following elements of HTML are
obsolete.  It is recommended that
client implementors implement the
obsolete forms for compatibility
with old servers.
\subsubsection{Plaintext}Status: Obsolete . \par 
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.\par 
An example if its use is:
\begin{verbatim}			<PLAINTEXT>
			0001 This is line one of a ling listing
			0002 file from <any@host.inc.com> which is sent

\end{verbatim}
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.
\subsubsection{XMP and LISTING:   Example sections}Status:  Obsolete . This are in use
and should be recognised by browers.
New servers should use $<$PRE$>$ instead.\par 
These styles allow text of fixed-width
characters to be embedded absolutely
as is into the document. The syntax
is:
\begin{verbatim}			<LISTING>
				...
			</LISTING>

\end{verbatim}
or 
\begin{verbatim}			<XMP>
				...
			</XMP>

\end{verbatim}
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:
\begin{itemize}
\item The text may contain any ISO Latin
printable characters, but not the
end tag opener. (See Historical note
)
\item 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.
\item 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.
\end{itemize}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.
\subsubsection{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
.
\paragraph{Examples of use:}
\begin{verbatim}		<HP1>...</HP1>   <HP2>... </HP2> etc.

\end{verbatim}

\subsubsection{Comment element}Status: Obsolete\par 
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.





\subsection{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.\par 
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





\chapter{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.
\begin{DL}{allow this much space}
\item[$<$
] The less than sign $<$
\item[$>$
] The "greater than" sign $>$
\item[\&amp;
] The ampersand sign \& itself.
\item[\&quot;
] The double quote sign "
\end{DL}
Also allowed are references to any
of the ISO Latin-1 alphabet, using
the entity names in the following
table.



\section{ISO Latin 1 character entities}This list is derived from "ISO 8879:1986//ENTITIES
Added Latin 1//EN".
\begin{DL}{allow this much space}
\item[\&AElig;
]capital AE diphthong (ligature)
\item[\&Aacute;
]capital A, acute accent
\item[\&Acirc;
]capital A, circumflex accent
\item[\&Agrave;
]capital A, grave accent
\item[\&Aring;
]capital A, ring
\item[\&Atilde;
]capital A, tilde
\item[\&Auml;
]capital A, dieresis or umlaut
mark
\item[\&Ccedil;
]capital C, cedilla
\item[\&ETH;
]capital Eth, Icelandic
\item[\&Eacute;
]capital E, acute accent
\item[\&Ecirc;
]capital E, circumflex accent
\item[\&Egrave;
]capital E, grave accent
\item[\&Euml;
]capital E, dieresis or umlaut
mark
\item[\&Iacute;
]capital I, acute accent
\item[\&Icirc;
]capital I, circumflex accent
\item[\&Igrave;
]capital I, grave accent
\item[\&Iuml;
]capital I, dieresis or umlaut
mark
\item[\&Ntilde;
]capital N, tilde
\item[\&Oacute;
]capital O, acute accent
\item[\&Ocirc;
]capital O, circumflex accent
\item[\&Ograve;
]capital O, grave accent
\item[\&Oslash;
]capital O, slash
\item[\&Otilde;
]capital O, tilde
\item[\&Ouml;
]capital O, dieresis or umlaut
mark
\item[\&THORN;
]capital THORN, Icelandic
\item[\&Uacute;
]capital U, acute accent
\item[\&Ucirc;
]capital U, circumflex accent
\item[\&Ugrave;
]capital U, grave accent
\item[\&Uuml;
]capital U, dieresis or umlaut
mark
\item[\&Yacute;
]capital Y, acute accent
\item[\&aacute;
]small a, acute accent
\item[\&acirc;
]small a, circumflex accent
\item[\&aelig;
]small ae diphthong (ligature)
\item[\&agrave;
]small a, grave accent
\item[\&aring;
]small a, ring
\item[\&atilde;
]small a, tilde
\item[\&auml;
]small a, dieresis or umlaut mark
\item[\&ccedil;
]small c, cedilla
\item[\&eacute;
]small e, acute accent
\item[\&ecirc;
]small e, circumflex accent
\item[\&egrave;
]small e, grave accent
\item[\&eth;
]small eth, Icelandic
\item[\&euml;
]small e, dieresis or umlaut mark
\item[\&iacute;
]small i, acute accent
\item[\&icirc;
]small i, circumflex accent
\item[\&igrave;
]small i, grave accent
\item[\&iuml;
]small i, dieresis or umlaut mark
\item[\&ntilde;
]small n, tilde
\item[\&oacute;
]small o, acute accent
\item[\&ocirc;
]small o, circumflex accent
\item[\&ograve;
]small o, grave accent
\item[\&oslash;
]small o, slash
\item[\&otilde;
]small o, tilde
\item[\&ouml;
]small o, dieresis or umlaut mark
\item[\&szlig;
]small sharp s, German (sz ligature)
\item[\&thorn;
]small thorn, Icelandic
\item[\&uacute;
]small u, acute accent
\item[\&ucirc;
]small u, circumflex accent
\item[\&ugrave;
]small u, grave accent
\item[\&uuml;
]small u, dieresis or umlaut mark
\item[\&yacute;
]small y, acute accent
\item[\&yuml;
]small y, dieresis or umlaut mark
\end{DL}







\chapter{The HTML DTD}The HTML DTD follows . Its relationship
to the content of an SGML document
is explained in the section "HTML
and SGML" .





\begin{verbatim}
<!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
                  13  1   13
                  14  18  UNUSED
                  32  95  32
                  127 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 [
<!--
 $Id: html.dtd,v 1.3 93/01/06 18:38:10 connolly Exp $
-->

<!--	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 | <A
NAME=z29 HREF="Lists.html#z36">MENU ">
<!ENTITY % literal " XMP | LISTING ">

<!ENTITY % headelement
	 " TITLE | NEXTID | ISINDEX" >

<!ENTITY % bodyelement
	 "P | A | %heading |
	 %list | DL | HEADERS | ADDRESS | PRE | BLOCKQUOTE
	| %literal">

<!ENTITY % oldstyle "%headelement | %bodyelement | #PCDATA">

<!-- Characters from various Latin alphabets. -->
<!ENTITY % ISOlat1 PUBLIC
	"ISO 8879:1986//ENTITIES Added Latin 1//EN">
%ISOlat1;


<!-- Document Element -->

<!ELEMENT HTML 0 0  ( HEAD | BODY | %oldstyle )*>

<!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 - 0 EMPTY
	  -- WWW clients should offer the option to perform a search on
	     documents containing ISINDEX.
	  -->
 
<!ELEMENT NEXTID - 0 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 - 0 EMPTY>
<!ATTLIST LINK

	NAME NMTOKEN #IMPLIED
	HREF %URL; #IMPLIED
        REL CDATA #IMPLIED -- type of relashionship
	REV CDATA #IMPLIED -- type of relashionship
                              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, ... --

	>
	
<!ELEMENT BASE - 0 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;">

<!ELEMENT BODY - -  (%bodyelement|%text;)*>

<!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.)
	-->

<!ELEMENT A	- -  (#PCDATA)>
<!ATTLIST A
        NAME NMTOKEN #IMPLIED
	HREF %URL ; #IMPLIED
        REL CDATA #IMPLIED 
	REV CDATA #IMPLIED -- type of relashionship:
				PARENT CHILD, SIBLING, NEXT, TOP,
				 DEFINITION, UPDATE, ORIGINAL etc.--

	URN CDATA #IMPLIED -- uniform resource number --
	TITLE CDATA #IMPLIED -- advisory only --
	METHODS NAMES #IMPLIED -- supportedpublic methods of the object:
					TEXTSEARCH, GET, HEAD, ... --
	>

<!ELEMENT IMG    - 0 EMPTY --  Embedded image -->
<!ATTLIST IMG
        SRC %URL ; #IMPLIED	-- URL of document to embed --
	>

<!ENTITY % htext "A | %text">

<!ELEMENT P	- 0 EMPTY -- separates paragraphs -->

<!ELEMENT ( %heading )	- -  (%text;|A)+>

<!ELEMENT HEADERS - - (DT | #PCDATA | DD | A)+>
<!ELEMENT DL	- -  (DT | DD | P | %htext;)*>
<!--	Content should match ((DT,(%htext;)+)+,(DD,(%htext;)+))
	But mixed content is messy.
  -->
 
<!ELEMENT DT	- 0 EMPTY>
<!ELEMENT DD	- 0 EMPTY>

<!ELEMENT (%list) - -  (%htext;|LI|P)+>
<!--	Content should match ((LI,(%htext;)+)+)
	But mixed content is messy.
  -->
<!ATTLIST (%list)
	COMPACT NAME #IMPLIED -- COMPACT, etc.--
	>

<!ELEMENT LI	- 0 EMPTY>

<!ELEMENT BLOCKQUOTE - - (%htext;|P)+
	-- for quoting some other source -->
<!ATTLIST BLOCKQUOTE
	>

<!ELEMENT ADDRESS - - (%htext;|P)+>

<!ELEMENT PRE - - (%htext|P)+>
<!ATTLIST PRE
	WIDTH NUMBER #implied
        >

<!-- deprecated elements -->

<!ELEMENT (%literal) - -  RCDATA>

<!ELEMENT PLAINTEXT - 0 EMPTY>

<!-- Local Variables: -->
<!-- mode: sgml -->
<!-- compile-command: "sgmls -s -p " -->
<!-- end: -->
]>


\end{verbatim}






\chapter{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.\par 
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-".\par 
These values of the REL attribute
of hypertext links have a significance
defined here, and may be treated
in special ways by HTML applications.\par 
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.\par 
In the explanations which follows,
A is the source document of the link
and B is the destination document
specified by the HREF attribute.\par 
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.
\section{Relationships between documents}These relationships are between the
documents themselves rather than
the subjects of the documents.
\subsection{UseIndex}B is a related index for a search
by a user reading this document who
asks for an index search function.\par 
A document may have any number of
index links, causing several indexes
top be searched in a client-defined
manner.\par 
B must support SEARCH operations
under its access protocol.
\subsection{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).\par 
A document may have any number of
glossary links.
\subsection{Annotation}The information in B is additional
to and subsidiary to that in A. \par 
Annotation is used by one person
to write the equivalent of "margin
notes" or other criticism on another's
document, for example.\par 
Example: The relationship between
a newsgroup and its articles.\par 
Acyclic.
\subsection{Reply}Similar to Annotation, but there
is no suggestion that B is subsidiary
to A: A and B are on equal footings.\par 
Example: The relationship between
a mail message and its reply, a news
article and its reply.\par 
Acyclic.
\subsection{Embed}If this link is followed, the node
at the end of it is embedded into
the display of the source document.\par 
Acyclic.
\subsection{Precedes}In an ordered structure defined by
the author, A precedes B, B is followed
by A.\par 
Acyclic. \par 
Any document may only have one link
of this relationship, and/or one
link of the reverse relationship.\par 
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.
\subsection{Subdocument}B is a lower part in the author's
hierarchy to A.  Acyclic. See also
Precedes.
\subsection{Present}Whenever A is presented, B must also
be presented.  This implies that
whenever A is retrieved, B must also
be retrieved.
\subsection{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
\subsection{Supersedes}B is a previous version of  A. \par 
Acyclic.
\subsection{History}B is a list of versions of A\par 
A link reverse link must exist from
B to A and to all other known versions
of A. 
\section{Relationships about subjects of documents}These relationships convey semantics
about objects described by documents,
rather than the documents themselves.
\subsection{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.\par 
Acyclic.
\subsection{Made}Person (etc) described by node A
is author of, or is responsible for
B\par 
This information can be used for
protection, and informing authors
of interest, for sending mail to
authors, etc.
\subsection{Interested}Person (etc) described by A is interested
in node B\par 
This information can be used for
informing readers of changes.





\chapter{Registration Authority}The HTTP Registration Authority is
responsible for maintaining lists
of:
\begin{itemize}
\item Relationship names for link and anchor
elements
\end{itemize}It is proposed that the Internet
Assigned Numbers Authority or their
successors take this role.\par 
Unregistered values may be used for
experimental purposes if they are
start with "X-".





\chapter{References	}
\begin{DL}{allow this much space}
\item[SGML
] ISO 8879:1986, Information ProcessingText
and Office SystemsStandard Generalized
Markup Language (SGML).
\item[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
.
\item[WWW
] The World-Wide Web , a global
information initiative. For boostrap
information, telnet info.cern.ch
or find documents by ftp://info.cern.ch/pub/www/doc
\item[URL
] Universal Resource Locators.
RFCxxx.  Currently  available by
anonymous FTP from info.cern.ch in
/pub/ietf.
\end{DL}






\chapter{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.
\begin{verbatim}				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


\end{verbatim}

\end{document}