\input texinfo    @c -*-texinfo-*-









@c %%**start of header
@setfilename snafu.info
@settitle Hypertext Markup Language - 2.0 
@setchapternewpage on
@c %%**end of header

@ifinfo
Status of this Memo

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 draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time.  It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''

To learn the current status of any Internet-Draft, please check the
@emph{1id-abstracts.txt} listing contained in the Internet-Drafts Shadow
Directories on @emph{ftp.is.co.za} (Africa), @emph{nic.nordu.net}
(Europe), @emph{munnari.oz.au} (Pacific Rim), @emph{ds.internic.net} (US
East Coast), or @emph{ftp.isi.edu} (US West Coast).

Distribution of this document is unlimited.  Please send comments to
the HTML working group (HTML-WG) of the Internet Engineering Task
Force (IETF) at @emph{html-wg@@oclc.org}.  Discussions of the group are
archived at @emph{http://www.acl.lanl.gov/HTML_WG/archives.html}.
@end ifinfo
@iftex
@emergencystretch=@hsize
@end iftex
@titlepage
@title Hypertext Markup Language - 2.0 
@subtitle September 22, 1995 
@author T@.  Berners-Lee (1)
@author D@.  Connolly (1)
@author (1) MIT/W3C 
@page
@vskip 0pt plus 1filll
Status of this Memo

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 draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time.  It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''

To learn the current status of any Internet-Draft, please check the
@emph{1id-abstracts.txt} listing contained in the Internet-Drafts Shadow
Directories on @emph{ftp.is.co.za} (Africa), @emph{nic.nordu.net}
(Europe), @emph{munnari.oz.au} (Pacific Rim), @emph{ds.internic.net} (US
East Coast), or @emph{ftp.isi.edu} (US West Coast).

Distribution of this document is unlimited.  Please send comments to
the HTML working group (HTML-WG) of the Internet Engineering Task
Force (IETF) at @emph{html-wg@@oclc.org}.  Discussions of the group are
archived at @emph{http://www.acl.lanl.gov/HTML_WG/archives.html}.
@end titlepage
@headings single
@node Top,Introduction,(dir),(dir)
@ifinfo
Hypertext Markup Language - 2.0 
@end ifinfo


@menu
* Introduction::
* Terms::
* HTML as an Application of SGML::
* HTML as an Internet Media Type::
* Document Structure::
* Characters; Words; and Paragraphs::     Characters, Words, and Paragraphs
* Hyperlinks::
* Forms::
* HTML Public Text::
* Security Considerations::
* References::
* Acknowledgments::
* The HTML Coded Character Set::
* Proposed Entities::
@end menu
@node Introduction,Terms,Top,Top
@chapter Introduction
The HyperText Markup Language (HTML) is a simple data format
used to create hypertext documents that are portable from one platform
to another.  HTML documents are SGML documents with generic semantics
that are appropriate for representing information from a wide range of
domains.

As HTML is an application of SGML, this specification assumes a
working knowledge of [SGML].


@menu
* Scope::
* Conformance::
@end menu
@node Scope,Conformance,Introduction,Introduction
@section Scope
HTML has been in use by the World-Wide Web (WWW) global information
initiative since 1990.  Previously, informal documentation on HTML has
been available from a number of sources on the Internet.  This
specification brings together, clarifies, and formalizes a set of
features that roughly corresponds to the capabilities of HTML in
common use prior to June 1994.  A number of new features to HTML are
being proposed and experimented in the Internet community.

This document thus defines a HTML 2.0 (to distinguish it from the
previous informal specifications).  Future (generally upwardly
compatible) versions of HTML with new features will be released with
higher version numbers.

HTML is an application of ISO Standard 8879:1986 @emph{Information
Processing Text and Office Systems;  Standard Generalized Markup
Language} (SGML).  The HTML Document Type Definition (DTD) is a
formal definition of the HTML syntax in terms of SGML.

This specification also defines HTML as an Internet Media Type[IMEDIA]
and MIME Content Type[MIME] called @samp{text/html}.  As such, it
defines the semantics of the HTML syntax and how that syntax should be
interpreted by user agents.


@node Conformance,,Scope,Introduction
@section Conformance
This specification governs the syntax of HTML documents and aspects of
the behavior of HTML user agents.


@menu
* Documents::
* Feature Test Entities::
* User Agents::
@end menu
@node Documents,Feature Test Entities,Conformance,Conformance
@subsection Documents
A document is a conforming HTML document if:

@itemize @bullet
@item
It is a conforming SGML document, and it conforms to the HTML DTD
(see @ref{HTML DTD}).
@footnote{There are a number of syntactic idioms that are not supported or
are supported inconsistently in some historical user agent
implementations.  These idioms are identified in notes like this
throughout this specification.}

@item
It conforms to the application conventions in this
specification.  For example, the value of the @emph{HREF} attribute of
the @emph{A} element must conform to the URI syntax.

@item
Its document character set includes [ISO-8859-1] and agrees with
[ISO-10646];  that is, each code position listed in @ref{The HTML Coded Character Set} is included, and each code position in the document
character set is mapped to the same character as [ISO-10646] designates
for that code position.
@footnote{The document character set is somewhat independent of the
character encoding scheme used to represent a document.  For example,
the @samp{ISO-2022-JP} character encoding scheme can be used for HTML
documents, since its repertoire is a subset of the [ISO-10646]
repertoire.  The critical distinction is that numeric character
references agree with [ISO-10646] regardless of how the document is encoded.}

@end itemize


@node Feature Test Entities,User Agents,Documents,Conformance
@subsection Feature Test Entities
The HTML DTD defines a standard HTML document type and several
variations, by way of feature test entities.  Feature test entities
are declarations in the HTML DTD that control the inclusion or
exclusion of portions of the DTD.

@table @emph
@item HTML.Recommended
Certain features of the language are
necessary for compatibility with widespread usage, but they may
compromise the structural integrity of a document.  This feature test
entity selects a more prescriptive document type definition that
eliminates those features.  It is set to @samp{IGNORE} by default.

For example, in order to preserve the structure of a document, an
editing user agent may translate HTML documents to the recommended
subset, or it may require that the documents be in the recommended
subset for import.

@item HTML.Deprecated
Certain features of the language are
necessary for compatibility with earlier versions of the
specification, but they tend to be used and implemented inconsistently,
and their use is deprecated.  This feature test entity enables a
document type definition that allows these features.
It is set to @samp{INCLUDE} by default.

Documents generated by translation software or editing software should
not contain deprecated idioms.

@end table


@node User Agents,,Feature Test Entities,Conformance
@subsection User Agents
An HTML user agent conforms to this specification if:

@itemize @bullet
@item
It parses the characters of an HTML document into data characters
and markup according to [SGML].
@footnote{In the interest of robustness and extensibility, there are a number
of widely deployed conventions for handling non-conforming documents.
See @ref{Undeclared Markup Error Handling} for details.}

@item
It supports the @samp{ISO-8859-1} character encoding scheme and
processes each character in the ISO Latin Alphabet No.  1 as specified
in @ref{The HTML Document Character Set}.
@footnote{To support non-western writing systems, HTML user agents are
encouraged to support @samp{ISO-10646-UCS-2} or similar character
encoding schemes and as much of the character repertoire of
[ISO-10646] as is practical.}

@item
It behaves identically for documents whose parsed token sequences
are identical.

For example, comments and the whitespace in tags disappear during
tokenization, and hence they do not influence the behavior of
conforming user agents.

@item
It allows the user to traverse (or at least attempt to traverse,
resources permitting) all hyperlinks from @emph{A} elements in an HTML
document.

@end itemize

An HTML user agent is a level 2 user agent if, additionally:

@itemize @bullet
@item
It allows the user to express all form field values specified in
an HTML document and to (attempt to) submit the values as requests to
information services.
@end itemize


@node Terms,HTML as an Application of SGML,Introduction,Top
@chapter Terms

@table @emph
@item absolute URI
a URI in absolute form;  for example, as per [URL]

@item anchor
one of two ends of a hyperlink;  typically, a phrase
marked as an @emph{A} element.

@item base URI
an absolute URI used in combination with a relative
URI to determine another absolute URI.

@item character
An atom of information, for example a letter or a
digit.  Graphic characters have associated glyphs, whereas control
characters have associated processing semantics.

@item character encoding scheme
A function whose domain is the set of
sequences of octets, and whose range is the set of sequences of
characters from a character repertoire;  that is, a sequence of octets
and a character encoding scheme determines a sequence of characters.

@item character repertoire
A finite set of characters;  e.g.  the range
of a coded character set.

@item code position
An integer.  A coded character set and a code
position from its domain determine a character.

@item coded character set
A function whose domain is a subset of the
integers and whose range is a character repertoire.  That is, for some
set of integers (usually of the form @{0, 1, 2, ..., N@} ), a coded
character set and an integer in that set determine a
character.  Conversely, a character and a coded character set determine
the character's code position (or, in rare cases, a few code
positions).

@item conforming HTML user agent
A user agent that conforms to this
specification in its processing of the Internet Media Type
@samp{text/html}.

@item data character
Characters other than markup, which make up the
content of elements.

@item document character set
a coded character set whose range
includes all characters used in a document.  Every SGML document has
exactly one document character set.  Numeric character references are
resolved via the document character set.

@item DTD
document type definition.  Rules that apply SGML to the
markup of documents of a particular type, including a set of element
and entity declarations.  [SGML]

@item element
A component of the hierarchical structure defined by a
document type definition;  it is identified in a document instance by
descriptive markup, usually a start-tag and end-tag.  [SGML]

@item end-tag
Descriptive markup that identifies the end of an
element.  [SGML]

@item entity
data with an associated notation or interpretation;  for
example, a sequence of octets associated with an Internet Media
Type.  [SGML]

@item fragment identifier
the portion of an @emph{HREF} attribute
value following the @samp{#} character which modifies the presentation
of the destination of a hyperlink.

@item form data set
a sequence of name/value pairs;  the names are
given by an HTML document and the values are given by a user.

@item HTML document
An SGML document conforming to this document type
definition.

@item hyperlink
a relationship between two anchors, called the head
and the tail.  The link goes from the tail to the head.  The head
and tail are also known as destination and source, respectively.

@item markup
Syntactically delimited characters added to the data of a
document to represent its structure.  There are four different kinds of
markup:  descriptive markup (tags), references, markup declarations,
and processing instructions.  [SGML]

@item may
A document or user interface is conforming whether this
statement applies or not.

@item media type
an Internet Media Type, as per [IMEDIA].

@item message entity
a head and body.  The head is a collection of
name/value fields, and the body is a sequence of octets.  The head
defines the content type and content transfer encoding of the body.  [MIME]

@item minimally conforming HTML user agent
A user agent that conforms
to this specification except for form processing.  It may only process
level 1 HTML documents.

@item must
Documents or user agents in conflict with this statement
are not conforming.

@item numeric character reference
markup that refers to a character
by its code position in the document character set.

@item SGML document
A sequence of characters organized physically as a
set of entities and logically into a hierarchy of elements.  An SGML
document consists of data characters and markup;  the markup describes
the structure of the information and an instance of that
structure.  [SGML]

@item shall
If a document or user agent conflicts with this statement,
it does not conform to this specification.

@item should
If a document or user agent conflicts with this
statement, undesirable results may occur in practice even though it
conforms to this specification.

@item start-tag
Descriptive markup that identifies the start of an
element and specifies its generic identifier and attributes.  [SGML]

@item syntax-reference character set
A coded character set whose range
includes all characters used for markup;  e.g.  name characters and
delimiter characters.

@item tag
Markup that delimits an element.  A tag includes a name which
refers to an element declaration in the DTD, and may include
attributes.  [SGML]

@item text entity
A finite sequence of characters.  A text entity
typically takes the form of a sequence of octets with some associated
character encoding scheme, transmitted over the network or stored in a
file.  [SGML]

@item typical
Typical processing is described for many elements.  This
is not a mandatory part of the specification but is given as guidance
for designers and to help explain the uses for which the elements were
intended.

@item URI
A Uniform Resource Identifier is a formatted string that
serves as an identifier for a resource, typically on the Internet.  URIs
are used in HTML to identify the anchors of hyperlinks.  URIs in
common practice include Uniform Resource Locators (URLs)[URL]
and Relative URLs [RELURL].

@item user agent
A component of a distributed system that presents
an interface and processes requests on behalf of a user;  for example,
a www browser or a mail user agent.

@item WWW
The World-Wide Web is a hypertext-based, distributed
information system created by researchers at CERN in
Switzerland.  @emph{http://www.w3.org/}

@end table


@node HTML as an Application of SGML,HTML as an Internet Media Type,Terms,Top
@chapter HTML as an Application of SGML

HTML is an application of ISO 8879:1986 --- Standard
Generalized Markup Language (SGML).  SGML is a system for defining
structured document types and markup languages to represent instances
of those document types[SGML].  The public text --- DTD and SGML
declaration --- of the HTML document type definition are provided in
@ref{HTML Public Text}.

The term @emph{HTML} refers to both the document type defined here and
the markup language for representing instances of this document type.


@menu
* SGML Documents::
* HTML Lexical Syntax::
* HTML Public Text Identifiers::
* Example HTML Document::
@end menu
@node SGML Documents,HTML Lexical Syntax,HTML as an Application of SGML,HTML as an Application of SGML
@section SGML Documents
An HTML document is an SGML document;  that is, a sequence of
characters organized physically into a set of entities, and logically
as a hierarchy of elements.

In the SGML specification, the first production of the SGML syntax
grammar separates an SGML document into three parts:  an SGML
declaration, a prologue, and an instance.  For the purposes of this
specification, the prologue is a DTD@.  This DTD describes another
grammar:  the start symbol is given in the doctype declaration, the
terminals are data characters and tags, and the productions are
determined by the element declarations.  The instance must conform to
the DTD, that is, it must be in the language defined by this grammar.

The SGML declaration determines the lexicon of the grammar.  It
specifies the document character set, which determines a
character repertoire that contains all characters that occur in all
text entities in the document, and the code positions associated with
those characters.

The SGML declaration also specifies the syntax-reference character set
of the document, and a few other parameters that bind the abstract
syntax of SGML to a concrete syntax.  This concrete syntax determines
how the sequence of characters of the document is mapped to a sequence
of terminals in the grammar of the prologue.

For example, consider the following document:

@example
<!DOCTYPE html PUBLIC "-//IETF//DTD HTML 2.0//EN">
<title>Parsing Example</title>
<p>Some text. <em>&#42;wow&#42;</em></p>
@end example

An HTML user agent should use the SGML declaration that is given in
@ref{SGML Declaration for HTML}.  According to its document character set,
@samp{&#42;} refers to an asterisk character, @samp{*}.

The instance above is regarded as the following sequence of terminals:

@enumerate
@item
start-tag:  TITLE
@item
data characters:  ``Parsing Example''
@item
end-tag:  TITLE
@item
start-tag:  P
@item
data characters ``Some text.  ''
@item
start-tag:  EM
@item
data characters:  ``*wow*''
@item
end-tag:  EM
@item
end-tag:  P
@end enumerate

The start symbol of the DTD grammar is HTML, and the productions
are given in the public text identified by @samp{-//IETF//DTD HTML 2.0//EN} (@ref{HTML DTD}).  The terminals above parse as:

@example
   HTML
    |
    \-HEAD
    |  |
    |  \-TITLE
    |      |
    |      \-<TITLE>
    |      |
    |      \-"Parsing Example"
    |      |
    |      \-</TITLE>
    |
    \-BODY
      |
      \-P
        |
        \-<P>
        |
        \-"Some text. "
        |
        \-EM
        |  |
        |  \-<EM>
        |  |
        |  \-"*wow*"
        |  |
        |  \-</EM>
        | 
        \-</P>
@end example

Some of the elements are delimited explicitly by tags, while the
boundaries of others are inferred.  The @emph{HTML} element contains a
@emph{HEAD} element and a @emph{BODY} element.  The @emph{HEAD} contains
@emph{TITLE}, which is explicitly delimited by start- and end-tags.


@node HTML Lexical Syntax,HTML Public Text Identifiers,SGML Documents,HTML as an Application of SGML
@section HTML Lexical Syntax
SGML specifies an abstract syntax and a reference concrete
syntax.  Aside from certain quantities and capacities (e.g.  the limit
on the length of a name), all HTML documents use the reference
concrete syntax.  In particular, all markup characters are in the
repertoire of [ISO-646].  Data characters are drawn from the document
character set (see @ref{Characters; Words; and Paragraphs}).

A complete discussion of SGML parsing, e.g.  the mapping of a sequence
of characters to a sequence of tags and data, is left to the SGML
standard[SGML].  This section is only a summary.


@menu
* Data Characters::
* Tags::
* Names::
* Attributes::
* Comments::
@end menu
@node Data Characters,Tags,HTML Lexical Syntax,HTML Lexical Syntax
@subsection Data Characters
Any sequence of characters that do not constitute markup (see
9.6 ``Delimiter Recognition'' of [SGML]) are mapped directly to
strings of data characters.  Some markup also maps to data character
strings.  Numeric character references map to single-character
strings, via the document character set.  Each reference to one of the
general entities defined in the HTML DTD maps to a
single-character string.

For example,

@example
abc&lt;def    => "abc","<","def"
abc&#60;def   => "abc","<","def"
@end example

The terminating semicolon on entity or numeric character references is
only necessary when the character following the reference would
otherwise be recognized as part of the name (see 9.4.5 ``Reference End''
in [SGML]).

@example
abc &lt def     => "abc ","<"," def"
abc &#60 def    => "abc ","<"," def"
@end example

An ampersand is only recognized as markup when it is followed by a
letter or a @samp{#} and a digit:

@example
abc & lt def    => "abc & lt def"
abc &# 60 def    => "abc &# 60 def"
@end example

A useful technique for translating plain text to HTML is to replace
each '<', '&', and '>' by an entity reference or numeric character
reference as follows:

@example
                 ENTITY      NUMERIC
       CHARACTER REFERENCE   CHAR REF     CHARACTER DESCRIPTION
       --------- ----------  -----------  ---------------------
         &       &amp;       &#38;        Ampersand 
         <       &lt;        &#60;        Less than
         >       &gt;        &#62;        Greater than
@end example

@footnote{There are SGML mechanisms, CDATA and RCDATA declared content, that
allow most @samp{<}, @samp{>}, and @samp{&} characters to be
entered without the use of entity references.  Because these mechanisms
tend to be used and implemented inconsistently, and because they
conflict with techniques for reducing HTML to 7 bit ASCII for
transport, they are deprecated in this version of HTML@.  See @ref{Example and Listing;  XMP; LISTING}.}


@node Tags,Names,Data Characters,HTML Lexical Syntax
@subsection Tags
Tags delimit elements such as headings, paragraphs, lists, character
highlighting, and links.  Most HTML elements are identified in a
document as a start-tag, which gives the element name and attributes,
followed by the content, followed by the end tag.  Start-tags are
delimited by @samp{<} and @samp{>};  end tags are delimited by
@samp{</} and @samp{>}.  An example is:

@example
<H1>This is a Heading</H1>
@end example

Some elements only have a start-tag without an end-tag.  For example,
to create a line break, use the @samp{<BR>} tag.  Additionally,
the end tags of some other elements, such as Paragraph
(@samp{</P>}), List Item (@samp{</LI>}), Definition Term
(@samp{</DT>}), and Definition Description (@samp{</DD>})
elements, may be omitted.

The content of an element is a sequence of data character strings and nested 
elements.  Some elements, such as anchors, cannot be nested.  Anchors 
and character highlighting may be put inside other constructs.  See
the HTML DTD, @ref{HTML DTD} for full details.
@footnote{The SGML declaration for HTML specifies SHORTTAG YES, which
means that there are other valid syntaxes for tags, such as NET tags,
@samp{<EM/.../};  empty start tags, @samp{<>};  and empty
end-tags, @samp{</>}.  Until support for these idioms is widely
deployed, their use is strongly discouraged.}


@node Names,Attributes,Tags,HTML Lexical Syntax
@subsection Names
A name consists of a letter followed by letters, digits, periods, or
hyphens.  The length of a name is limited to 72 characters by the
@samp{NAMELEN} parameter in the SGML declaration for HTML, @ref{SGML Declaration for HTML}.  Element and attribute names are not case sensitive, but
entity names are.  For example, @samp{<BLOCKQUOTE>},
@samp{<BlockQuote>}, and @samp{<blockquote>} are equivalent,
whereas @samp{&amp;} is different from @samp{&AMP;}.

In a start-tag, the element name must immediately follow the tag 
open delimiter @samp{<}.


@node Attributes,Comments,Names,HTML Lexical Syntax
@subsection Attributes
In a start-tag, white space and attributes are allowed between the
element name and the closing delimiter.  An attribute specification
typically consists of an attribute name, an equal sign, and a value,
though some attribute specifications may be just a name token.  White
space is allowed around the equal sign.

The value of the attribute may be either:

@itemize @bullet
@item
A string literal, delimited by single quotes or double quotes and
not containing any occurrences of the delimiting character.
@footnote{Some historical implementations consider any occurrence
of the @samp{>} character to signal the end of a tag.  For
compatibility with such implementations, when @samp{>} appears in an
attribute value, it should be represented with a numeric
character reference.  For example,
@samp{<IMG SRC="eq1.jpg" alt="a>b">} should be written
@samp{<IMG SRC="eq1.jpg" alt="a&#62;b">} or
@samp{<IMG SRC="eq1.jpg" alt="a&gt;b">}.}

@item
A name token (a sequence of letters, digits, periods, or hyphens).
Name tokens are not case sensitive.
@footnote{Some historical implementations allow any character 
except space or @samp{>} in a name token.}
@end itemize

In this example, @emph{img} is the element name, @emph{src} is the
attribute name, and @samp{http://host/dir/file.gif} is the
attribute value:

@example
<img src='http://host/dir/file.gif'>
@end example

A useful technique for computing an attribute value literal for a
given string is to replace each quote and white space character by an
entity reference or numeric character reference as follows:

@example
                 ENTITY      NUMERIC
       CHARACTER REFERENCE   CHAR REF     CHARACTER DESCRIPTION
       --------- ----------  -----------  ---------------------
         HT                  &#9;         Tab
         LF                  &#10;        Line Feed
         CR                  &#13;        Carriage Return
         SP                  &#32;        Space
         "       &quot;      &#34;        Quotation mark 
         &       &amp;       &#38;        Ampersand 
@end example

For example:

@example
<IMG SRC="image.jpg" alt="First &quot;real&quot; example">
@end example

The @samp{NAMELEN} parameter in the SGML declaration (@ref{SGML Declaration for HTML}) limits the length of an attribute value to 1024
characters.

Attributes such as ISMAP and COMPACT may be written using a minimized
syntax (see 7.9.1.2 ``Omitted Attribute Name'' in [SGML]).  The markup:

@example
<UL COMPACT="compact">
@end example

can be written using a minimized syntax:

@example
<UL COMPACT>
@end example

@noindent
@footnote{Some historical implementations only understand the 
minimized syntax.}


@node Comments,,Attributes,HTML Lexical Syntax
@subsection Comments
To include comments in an HTML document, use a comment declaration.  A
comment declaration consists of @samp{<!} followed by zero or more
comments followed by @samp{>}.  Each comment starts with @samp{--} and
includes all text up to and including the next occurrence of
@samp{--}.  In a comment declaration, white space is allowed after
each comment, but not before the first comment.  The entire comment
declaration is ignored.
@footnote{Some historical HTML implementations incorrectly consider 
any @samp{>} character to be the termination of a comment.}

For example:

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HEAD>
<TITLE>HTML Comment Example</TITLE>
<!-- Id: html-sgml.sgm,v 1.5 1995/05/26 21:29:50 connolly Exp  -->
<!-- another -- -- comment -->
<!>
</HEAD>
<BODY>
<p> <!- not a comment, just regular old data characters ->
@end example


@node HTML Public Text Identifiers,Example HTML Document,HTML Lexical Syntax,HTML as an Application of SGML
@section HTML Public Text Identifiers
To identify information as an HTML document conforming to this
specification, each document must start with one of the following
document type declarations.

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
@end example

This document type declaration refers to the HTML DTD in @ref{HTML DTD}.
@footnote{If the body of a @samp{text/html} message entity does not
begin with a document type declaration, an HTML user agent should
infer the above document type declaration.}

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Level 2//EN">
@end example

This document type declaration also refers to the HTML DTD which
appears in @ref{HTML DTD}.

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN">
@end example

This document type declaration refers to the level 1 HTML DTD in
@ref{Level 1 HTML DTD}.  Form elements must not occur in level 1
documents.

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Strict//EN">
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0 Strict Level 1//EN">
@end example

These two document type declarations refer to the HTML DTD in @ref{Strict HTML DTD} and @ref{Strict Level 1 HTML DTD}.  They refer to the more
structurally rigid definition of HTML.

HTML user agents may support other document types.  In particular,
they may support other formal public identifiers, or other document
types altogether.  They may support an internal declaration subset with
supplemental entity, element, and other markup declarations.


@node Example HTML Document,,HTML Public Text Identifiers,HTML as an Application of SGML
@section Example HTML Document

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML>
<!-- Here's a good place to put a comment. -->
<HEAD>
<TITLE>Structural Example</TITLE>
</HEAD><BODY>
<H1>First Header</H1>
<P>This is a paragraph in the example HTML file. Keep in mind 
that the title does not appear in the document text, but that 
the header (defined by H1) does.</P>
<OL>
<LI>First item in an ordered list.
<LI>Second item in an ordered list.
  <UL COMPACT>
  <LI> Note that lists can be nested;
  <LI> Whitespace may be used to assist in reading the 
       HTML source.
  </UL>
<LI>Third item in an ordered list.
</OL>
<P>This is an additional paragraph. Technically, end tags are 
not required for paragraphs, although they are allowed. You can 
include character highlighting in a paragraph. <EM>This sentence 
of the paragraph is emphasized.</EM> Note that the &lt;/P&gt; 
end tag has been omitted.
<P>
<IMG SRC ="triangle.xbm" alt="Warning: ">
Be sure to read these <b>bold instructions</b>.
</BODY></HTML>
@end example


@node HTML as an Internet Media Type,Document Structure,HTML as an Application of SGML,Top
@chapter HTML as an Internet Media Type
An HTML user agent allows users to interact with resources which have
HTML representations.  At a minimum, it must allow users to examine and
navigate the content of HTML level 1 documents.  HTML user agents
should be able to preserve all formatting distinctions represented in
an HTML document, and be able to simultaneously present resources
referred to by IMG elements (they may ignore some formatting
distinctions or IMG resources at the request of the user).  Level 2
HTML user agents should support form entry and submission.


@menu
* text/html media type::
* HTML Document Representation::
@end menu
@node text/html media type,HTML Document Representation,HTML as an Internet Media Type,HTML as an Internet Media Type
@section text/html media type

This specification defines the Internet Media Type[IMEDIA] (formerly
referred to as the Content Type[MIME]) called @samp{text/html}.  The
following is to be registered with [IANA].

@table @emph
@item Media Type name
text

@item Media subtype name
html

@item Required parameters
none

@item Optional parameters
level, charset

@item Encoding considerations
any encoding is allowed

@item Security considerations
see @ref{Security Considerations}

@noindent
@end table

The optional parameters are defined as follows:

@table @emph
@item Level
The level parameter specifies the feature set used in the
document.  The level is an integer number, implying that any features
of same or lower level may be present in the document.  Level 1 is all
features defined in this specification except those that require the
@emph{FORM} element.  Level 2 includes form processing.  Level 2 is the
default.

@item Charset
The charset parameter (as defined in section 7.1.1 of
RFC 1521[MIME]) may be given to specify the character encoding scheme
used to represent the HTML document as a sequence of octets.  The
default value is outside the scope of this specification;  but for
example, the default is @samp{US-ASCII} in the context of MIME mail,
and @samp{ISO-8859-1} in the context of HTTP [HTTP].

@end table


@node HTML Document Representation,,text/html media type,HTML as an Internet Media Type
@section HTML Document Representation
A message entity with a content type of @samp{text/html} represents
an HTML document, consisting of a single text entity.  The
@samp{charset} parameter (whether implicit or explicit) identifies a
character encoding scheme.  The text entity consists of the characters
determined by this character encoding scheme and the octets of the body of
the message entity.


@menu
* Undeclared Markup Error Handling::
* Conventional Representation of Newlines::
@end menu
@node Undeclared Markup Error Handling,Conventional Representation of Newlines,HTML Document Representation,HTML Document Representation
@subsection Undeclared Markup Error Handling
To facilitate experimentation and interoperability between
implementations of various versions of HTML, the installed base of
HTML user agents supports a superset of the HTML 2.0 language by
reducing it to HTML 2.0:  markup in the form of a start-tag or end-tag,
whose generic identifier is not declared is mapped to nothing during
tokenization.  Undeclared attributes are treated similarly.  The entire
attribute specification of an unknown attribute (i.e., the unknown
attribute and its value, if any) should be ignored.  On the other
hand, references to undeclared entities should be treated as data
characters.

For example:

@example
<div class=chapter><h1>foo</h1><p>...</div>
  => <H1>,"foo",</H1>,<P>,"..."
xxx <P ID=z23> yyy
  => "xxx ",<P>," yyy
Let &alpha; &amp; &beta; be finite sets.
  => "Let &alpha; & &beta; be finite sets."
@end example

Support for notifying the user of such errors is encouraged.

Information providers are warned that this convention is not binding:
unspecified behavior may result, as such markup does not conform to
this specification.


@node Conventional Representation of Newlines,,Undeclared Markup Error Handling,HTML Document Representation
@subsection Conventional Representation of Newlines
SGML specifies that a text entity is a sequence of records, each
beginning with a record start character and ending with a record end
character (code positions 10 and 13 respectively) (section
7.6.1, ``Record Boundaries'' in [SGML]).

[MIME] specifies that a body of type @samp{text/*} is a sequence of
lines, each terminated by CRLF, that is, octets 13, 10.

In practice, HTML documents are frequently represented and
transmitted using an end of line convention that depends on the
conventions of the source of the document;  frequently, that
representation consists of CR only, LF only, or a CR LF
sequence.  Hence the decoding of the octets will often result in
a text entity with some missing record start and record end
characters.

Since there is no ambiguity, HTML user agents are encouraged to
infer the missing record start and end characters.

An HTML user agent should treat end of line in any of its
variations as a word space in all contexts except
preformatted text.  Within preformatted text, an HTML user agent
should treat any of the three common representations of
end-of-line as starting a new line.


@node Document Structure,Characters; Words; and Paragraphs,HTML as an Internet Media Type,Top
@chapter Document Structure
An HTML document is a tree of elements, including a head and body,
headings, paragraphs, lists, etc.  Form elements are discussed in
@ref{Forms}.


@menu
* Document Element;  HTML::     Document Element:  HTML
* Head;  HEAD::     Head:  HEAD
* Body;  BODY::     Body:  BODY
* Headings;  H1 ...  H6::     Headings:  H1 ...  H6
* Block Structuring Elements::
* List Elements::
* Phrase Markup::
* Line Break;  BR::     Line Break:  BR
* Horizontal Rule;  HR::     Horizontal Rule:  HR
* Image;  IMG::     Image:  IMG
@end menu
@node Document Element;  HTML,Head;  HEAD,Document Structure,Document Structure
@section Document Element:  HTML
The HTML document element consists of a head and a body, much
like a memo or a mail message.  The head contains the
title and optional elements.  The body is a text flow
consisting of paragraphs, lists, and other elements.


@node Head;  HEAD,Body;  BODY,Document Element;  HTML,Document Structure
@section Head:  HEAD

The head of an HTML document is an unordered collection of
information about the document.  For example:

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HEAD>
<TITLE>Introduction to HTML</TITLE>
</HEAD>
...
@end example


@menu
* Title;  TITLE::     Title:  TITLE
* Base Address;  BASE::     Base Address:  BASE
* Keyword Index;  ISINDEX::     Keyword Index:  ISINDEX
* Link;  LINK::     Link:  LINK
* Associated Meta-information;  META::     Associated Meta-information:  META
* Next Id;  NEXTID::     Next Id:  NEXTID
@end menu
@node Title;  TITLE,Base Address;  BASE,Head;  HEAD,Head;  HEAD
@subsection Title:  TITLE

Every HTML document must contain a @emph{TITLE} element.

The title should identify the contents of the document in a global
context.  A short title, such as ``Introduction'' may be meaningless out
of context.  A title such as ``Introduction to HTML Elements'' is more
appropriate.
@footnote{The length of a title is not limited;  however, long titles may
be truncated in some applications.  To minimize this possibility,
titles should be fewer than 64 characters.}

A user agent may display the title of a document in a history list
or as a label for the window displaying the document.  This differs
from headings (@ref{Headings;  H1 ...  H6}), which are typically displayed
within the body text flow.


@node Base Address;  BASE,Keyword Index;  ISINDEX,Title;  TITLE,Head;  HEAD
@subsection Base Address:  BASE

The optional @emph{BASE} element provides a base address for
interpreting relative URLs when the document is read out of context
(see @ref{Hyperlinks}).  The value of the @emph{HREF} attribute
must be an absolute URI.


@node Keyword Index;  ISINDEX,Link;  LINK,Base Address;  BASE,Head;  HEAD
@subsection Keyword Index:  ISINDEX

The @emph{ISINDEX} element indicates that the user agent should
allow the user to search an index by giving keywords.  See @ref{Queries and Indexes} for details.


@node Link;  LINK,Associated Meta-information;  META,Keyword Index;  ISINDEX,Head;  HEAD
@subsection Link:  LINK

The @emph{LINK} element represents a hyperlink (see @ref{Hyperlinks}).  Any number of LINK elements may occur in the
@emph{HEAD} element of an HTML document.  It has the same attributes as
the @emph{A} element (see @ref{Anchor;  A}).

The @emph{LINK} element is typically used to indicate authorship,
related indexes and glossaries, older or more recent versions,
document hierarchy, associated resources such as style sheets, etc.


@node Associated Meta-information;  META,Next Id;  NEXTID,Link;  LINK,Head;  HEAD
@subsection Associated Meta-information:  META

The @emph{META} element is an extensible container for use in
identifying specialized document meta-information.  Meta-information
has two main functions:

@itemize @bullet
@item
to provide a means to discover that the data set exists and
how it might be obtained or accessed;  and 

@item
to document the content, quality, and features of a data set,
indicating its fitness for use.  
@end itemize

Each @emph{META} element specifies a name/value pair.  If multiple
META elements are provided with the same name, their combined
contents---concatenated as a comma-separated list---is the value
associated with that name.
@footnote{The @emph{META} element should not be used where a specific
element, such as @emph{TITLE}, would be more appropriate.  Rather
than a @emph{META} element with a URI as the value of the @emph{CONTENT}
attribute, use a @emph{LINK} element.}

HTTP servers may read the content of the document @emph{HEAD} to
generate header fields corresponding to any elements defining a value
for the attribute @emph{HTTP-EQUIV}.
@footnote{The method by which the server extracts document meta-information is
unspecified and not mandatory.  The @emph{META} element
only provides an extensible mechanism for identifying and embedding
document meta-information --- how it may be used is up to the individual
server implementation and the HTML user agent.}

Attributes of the META element:

@table @emph
@item HTTP-EQUIV
binds the element to an HTTP header
field.  An HTTP server may use this information to process the
document.  In particular, it may include a header field in the
responses to requests for this document:  the header name is
taken from the @emph{HTTP-EQUIV} attribute value, and the header value
is taken from the value of the @emph{CONTENT} attribute.  HTTP header
names are not case sensitive.

@item NAME
specifies the name of the name/value pair.  If not present,
@emph{HTTP-EQUIV} gives the name.

@item CONTENT
specifies the value of the name/value pair.

@end table

Examples

If the document contains:

@example
<META HTTP-EQUIV="Expires"
      CONTENT="Tue, 04 Dec 1993 21:29:02 GMT">
<meta http-equiv="Keywords" CONTENT="Fred">
<META HTTP-EQUIV="Reply-to"
      content="fielding@@ics.uci.edu (Roy Fielding)">
<Meta Http-equiv="Keywords" CONTENT="Barney">
@end example

then the server may include the following header fields:

@example
Expires: Tue, 04 Dec 1993 21:29:02 GMT
Keywords: Fred, Barney
Reply-to: fielding@@ics.uci.edu (Roy Fielding)
@end example

as part of the HTTP response to a @samp{GET} or @samp{HEAD} request
for that document.

An HTTP server must not use the @emph{META} element to form an HTTP
response header unless the @emph{HTTP-EQUIV} attribute is present.

An HTTP server may disregard any @emph{META} elements that specify
information controlled by the HTTP server, for example @samp{Server},
@samp{Date}, and @samp{Last-modified}.


@node Next Id;  NEXTID,,Associated Meta-information;  META,Head;  HEAD
@subsection Next Id:  NEXTID

The @emph{NEXTID} element is included for historical reasons only.
HTML documents should not contain @emph{NEXTID} elements.

The @emph{NEXTID} element gives a hint for the name to use for a
new @emph{A} element when editing an HTML document.  It should be
distinct from all @emph{NAME} attribute values on @emph{A}
elements.  For example:

@example
<NEXTID N=Z27>
@end example


@node Body;  BODY,Headings;  H1 ...  H6,Head;  HEAD,Document Structure
@section Body:  BODY

The @emph{BODY} element contains the text flow of the document,
including headings, paragraphs, lists, etc.

For example:

@example
<BODY>
<h1>Important Stuff</h1>
<p>Explanation about important stuff...
</BODY>
@end example


@node Headings;  H1 ...  H6,Block Structuring Elements,Body;  BODY,Document Structure
@section Headings:  H1 ...  H6

The six heading elements, @emph{H1} through @emph{H6}, denote section
headings.  Although the order and occurrence of headings is not
constrained by the HTML DTD, documents should not skip levels (for
example, from H1 to H3), as converting such documents to other
representations is often problematic.

Example of use:

@example
<H1>This is a heading</H1>
Here is some text
<H2>Second level heading</H2>
Here is some more text.
@end example

Typical renderings are:

@table @emph
@item H1
Bold, very-large font, centered.  One or two blank lines
above and below.

@item H2
Bold, large font, flush-left.  One or two blank lines
above and below.

@item H3
Italic, large font, slightly indented from the left
margin.  One or two blank lines above and below.

@item H4
Bold, normal font, indented more than H3.  One blank
line above and below.

@item H5
Italic, normal font, indented as H4.  One blank line
above.

@item H6
Bold, indented same as normal text, more than H5.  One
blank line above.

@end table


@node Block Structuring Elements,List Elements,Headings;  H1 ...  H6,Document Structure
@section Block Structuring Elements

Block structuring elements include paragraphs, lists, and block
quotes.  They must not contain heading elements, but they may contain
phrase markup, and in some cases, they may be nested.


@menu
* Paragraph;  P::     Paragraph:  P
* Preformatted Text;  PRE::     Preformatted Text:  PRE
* Address;  ADDRESS::     Address:  ADDRESS
* Block Quote;  BLOCKQUOTE::     Block Quote:  BLOCKQUOTE
@end menu
@node Paragraph;  P,Preformatted Text;  PRE,Block Structuring Elements,Block Structuring Elements
@subsection Paragraph:  P

The @emph{P} element indicates a paragraph.  The exact indentation,
leading space, etc.  of a paragraph is not specified and may be a
function of other tags, style sheets, etc.

Typically, paragraphs are surrounded by a vertical space of one
line or half a line.  The first line in a paragraph is indented in some
cases.

Example of use:

@example
<H1>This Heading Precedes the Paragraph</H1>
<P>This is the text of the first paragraph.
<P>This is the text of the second paragraph. Although you do not 
need to start paragraphs on new lines, maintaining this 
convention facilitates document maintenance.</P>
<P>This is the text of a third paragraph.</P>
@end example


@node Preformatted Text;  PRE,Address;  ADDRESS,Paragraph;  P,Block Structuring Elements
@subsection Preformatted Text:  PRE

The @emph{PRE} element represents a character cell block of text and
is suitable for text that has been formatted for a monospaced font.

The @emph{PRE} tag may be used with the optional @emph{WIDTH}
attribute.  The WIDTH attribute specifies the maximum number of
characters for a line and allows the HTML user agent to select a
suitable font and indentation.

Within preformatted text:

@itemize @bullet
@item
Line breaks within the text are rendered as a move to the
beginning of the next line.
@footnote{References to the ``beginning of a new line'' do not imply that
the renderer is forbidden from using a constant left indent for
rendering preformatted text.  The left indent may be constrained by the
width required.}

@item
Anchor elements and phrase markup may be used.
@footnote{Constraints on the processing of @emph{PRE} content may limit or
prevent the ability of the HTML user agent to faithfully render
phrase markup.}

@item
Elements that define paragraph formatting (headings, address,
etc.) must not be used.
@footnote{Some historical documents contain @emph{P} tags in @emph{PRE}
elements.  User agents are encouraged to treat this as a line break.  A
@emph{P} tag followed by a newline character should produce only one
line break, not a line break plus a blank line.}

@item
The horizontal tab character (code position 9 in the HTML document
character set) 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.  Documents should not contain tab
characters, as they are not supported consistently.
@end itemize

Example of use:

@example
<PRE>
Line 1.
       Line 2 is to the right of line 1.     <a href="abc">abc</a>
       Line 3 aligns with line 2.            <a href="def">def</a>
</PRE>
@end example


@menu
* Example and Listing;  XMP; LISTING::     Example and Listing:  XMP, LISTING
@end menu
@node Example and Listing;  XMP; LISTING,,Preformatted Text;  PRE,Preformatted Text;  PRE
@subsubsection Example and Listing:  XMP, LISTING

The @emph{XMP} and @emph{LISTING} elements are similar to the
@emph{PRE} element, but they have a different syntax.  Their content is
declared as CDATA, which means that no markup except the end-tag open
delimiter-in-context is recognized (see 9.6 ``Delimiter Recognition'' of
[SGML]).
@footnote{In a previous draft of the HTML specification, the syntax
of @emph{XMP} and @emph{LISTING} elements allowed closing tags to
be treated as data characters, as long as the tag name was not
@emph{XMP} or @emph{LISTING}, respectively.}

Since CDATA declared content has a number of unfortunate
interactions with processing techniques and tends to be used and
implemented inconsistently, HTML documents should not contain
@emph{XMP} nor @emph{LISTING} elements --- the @emph{PRE} tag is more
expressive and more consistently supported.

The @emph{LISTING} element should be rendered so that at least 132
characters fit on a line.  The @emph{XMP} element should be rendered so
that at least 80 characters fit on a line but is otherwise identical
to the @emph{LISTING} element.
@footnote{In a previous draft, HTML included a @emph{PLAINTEXT} element that
is similar to the @emph{LISTING} element, except that there is
no closing tag:  all characters after the @emph{PLAINTEXT} start-tag
are data.}


@node Address;  ADDRESS,Block Quote;  BLOCKQUOTE,Preformatted Text;  PRE,Block Structuring Elements
@subsection Address:  ADDRESS

The @emph{ADDRESS} element contains such information as address,
signature and authorship, often at the beginning or end of the body of
a document.

Typically, the @emph{ADDRESS} element is rendered in an italic
typeface and may be indented.

Example of use:

@example
<ADDRESS>
Newsletter editor<BR>
J.R. Brown<BR>
JimquickPost News, Jimquick, CT 01234<BR>
Tel (123) 456 7890
</ADDRESS>
@end example


@node Block Quote;  BLOCKQUOTE,,Address;  ADDRESS,Block Structuring Elements
@subsection Block Quote:  BLOCKQUOTE

The @emph{BLOCKQUOTE} element contains text quoted from another
source.

A typical rendering might be a slight extra left and right indent,
and/or italic font.  The @emph{BLOCKQUOTE} typically provides space
above and below the quote.

Single-font rendition may reflect the quotation style of Internet
mail by putting a vertical line of graphic characters, such as the
greater than symbol (>), in the left margin.

Example of use:

@example
I think the play ends
<BLOCKQUOTE>
<P>Soft you now, the fair Ophelia. Nymph, in thy orisons, be all 
my sins remembered.
</BLOCKQUOTE>
but I am not sure.
@end example


@node List Elements,Phrase Markup,Block Structuring Elements,Document Structure
@section List Elements

HTML includes a number of list elements.  They may be used in
combination;  for example, a @emph{OL} may be nested in an @emph{LI}
element of a @emph{UL}.

The @emph{COMPACT} attribute suggests that a compact rendering be
used.


@menu
* Unordered List;  UL; LI::     Unordered List:  UL, LI
* Ordered List;  OL::     Ordered List:  OL
* Directory List;  DIR::     Directory List:  DIR
* Menu List;  MENU::     Menu List:  MENU
* Definition List;  DL; DT; DD::     Definition List:  DL, DT, DD
@end menu
@node Unordered List;  UL; LI,Ordered List;  OL,List Elements,List Elements
@subsection Unordered List:  UL, LI

The @emph{UL} represents a list of items --- typically rendered
as a bulleted list.

The content of a @emph{UL} element is a sequence of @emph{LI}
elements.  For example:

@example
<UL>
<LI>First list item
<LI>Second list item
 <p>second paragraph of second item
<LI>Third list item
</UL>
@end example


@node Ordered List;  OL,Directory List;  DIR,Unordered List;  UL; LI,List Elements
@subsection Ordered List:  OL

The @emph{OL} element represents an ordered list of items, sorted by
sequence or order of importance.  It is typically rendered as a
numbered list.

The content of a @emph{OL} element is a sequence of @emph{LI}
elements.  For example:

@example
<OL>
<LI>Click the Web button to open URI window.
<LI>Enter the URI number in the text field of the Open URI 
window. The Web document you specified is displayed.
  <ol>
   <li>substep 1
   <li>substep 2
  </ol>
<LI>Click highlighted text to move from one link to another.
</OL>
@end example


@node Directory List;  DIR,Menu List;  MENU,Ordered List;  OL,List Elements
@subsection Directory List:  DIR

The @emph{DIR} element is similar to the @emph{UL} element.  It
represents a list of short items, typically up to 20 characters
each.  Items in a directory list may be arranged in columns, typically
24 characters wide.

The content of a @emph{DIR} element is a sequence of @emph{LI}
elements.  Nested block elements are not allowed in the content of
@emph{DIR} elements.  For example:

@example
<DIR>
<LI>A-H<LI>I-M
<LI>M-R<LI>S-Z
</DIR>
@end example


@node Menu List;  MENU,Definition List;  DL; DT; DD,Directory List;  DIR,List Elements
@subsection Menu List:  MENU

The @emph{MENU} element is a list of items with typically one line
per item.  The menu list style is typically more compact than the style
of an unordered list.

The content of a @emph{MENU} element is a sequence of @emph{LI}
elements.  Nested block elements are not allowed in the content of
@emph{MENU} elements.  For example:

@example
<MENU>
<LI>First item in the list.
<LI>Second item in the list.
<LI>Third item in the list.
</MENU>
@end example


@node Definition List;  DL; DT; DD,,Menu List;  MENU,List Elements
@subsection Definition List:  DL, DT, DD

A definition list is a list of terms and corresponding
definitions.  Definition lists are typically formatted with the term
flush-left and the definition, formatted paragraph style, indented
after the term.

The content of a @emph{DL} element is a sequence of @emph{DT}
elements and/or @emph{DD} elements, usually in pairs.  Multiple @emph{DT}
may be paired with a single @emph{DD} element.  Documents should not
contain multiple consecutive @emph{DD} elements.

Example of use:

@example
<DL>
<DT>Term<DD>This is the definition of the first term.
<DT>Term<DD>This is the definition of the second term.
</DL>
@end example

If the DT term does not fit in the DT column (typically one third
of the display area), it may be extended across the page with the DD
section moved to the next line, or it may be wrapped onto successive
lines of the left hand column.

The optional @emph{COMPACT} attribute suggests that a compact
rendering be used, because the list items are small and/or the entire
list is large.

Unless the @emph{COMPACT} attribute is present, an HTML user agent
may leave white space between successive DT, DD pairs.  The
@emph{COMPACT} attribute may also reduce the width of the left-hand
(DT) column.

@example
<DL COMPACT>
<DT>Term<DD>This is the first definition in compact format.
<DT>Term<DD>This is the second definition in compact format.
</DL>
@end example


@node Phrase Markup,Line Break;  BR,List Elements,Document Structure
@section Phrase Markup

Phrases may be marked up according to idiomatic usage,
typographic appearance, or for use as hyperlink anchors.

User agents must render highlighted phrases distinctly from plain
text.  Additionally, @emph{EM} content must be rendered as distinct from
@emph{STRONG} content, and @emph{B} content must rendered as distinct
from @emph{I} content.

Phrase elements may be nested within the content of other phrase
elements;  however, HTML user agents may render nested phrase
elements indistinctly from non-nested elements:

@example
plain <B>bold <I>italic</I></B> may be rendered 
the same as plain <B>bold </B><I>italic</I>
@end example


@menu
* Idiomatic Elements::
* Typographic Elements::
* Anchor;  A::     Anchor:  A
@end menu
@node Idiomatic Elements,Typographic Elements,Phrase Markup,Phrase Markup
@subsection Idiomatic Elements
Phrases may be marked up to indicate certain idioms.
@footnote{User agents may support the @emph{DFN} element, not
included in this specification, as it has been deployed to some extent.
It is used to indicate the defining instance of a term, and it is
typically rendered in italic or bold italic.}


@menu
* Citation;  CITE::     Citation:  CITE
* Code;  CODE::     Code:  CODE
* Emphasis;  EM::     Emphasis:  EM
* Keyboard;  KBD::     Keyboard:  KBD
* Sample;  SAMP::     Sample:  SAMP
* Strong Emphasis;  STRONG::     Strong Emphasis:  STRONG
* Variable;  VAR::     Variable:  VAR
@end menu
@node Citation;  CITE,Code;  CODE,Idiomatic Elements,Idiomatic Elements
@subsubsection Citation:  CITE

The @emph{CITE} element is used to indicate the title of a book or
other citation.  It is typically rendered as italics.  For example:

@example
He just couldn't get enough of <cite>The Grapes of Wrath</cite>.
@end example


@node Code;  CODE,Emphasis;  EM,Citation;  CITE,Idiomatic Elements
@subsubsection Code:  CODE

The @emph{CODE} element indicates an example of code, typically
rendered in a mono-spaced font.  The @emph{CODE} element is intended
for short words or phrases of code;  the @emph{PRE} block
structuring element (@ref{Preformatted Text;  PRE}) is more appropriate for
multiple-line listings.  For example:

@example
The expression <code>x += 1</code>
is short for <code>x = x + 1</code>.
@end example


@node Emphasis;  EM,Keyboard;  KBD,Code;  CODE,Idiomatic Elements
@subsubsection Emphasis:  EM

The @emph{EM} element indicates an emphasized phrase, typically
rendered as italics.  For example:

@example
A singular subject <em>always</em> takes a singular verb.
@end example


@node Keyboard;  KBD,Sample;  SAMP,Emphasis;  EM,Idiomatic Elements
@subsubsection Keyboard:  KBD

The @emph{KBD} element indicates text typed by a user, typically
rendered in a mono-spaced font.  This is commonly used in instruction
manuals.  For example:

@example
Enter <kbd>FIND IT</kbd> to search the database.
@end example


@node Sample;  SAMP,Strong Emphasis;  STRONG,Keyboard;  KBD,Idiomatic Elements
@subsubsection Sample:  SAMP

The @emph{SAMP} element indicates a sequence of literal characters,
typically rendered in a mono-spaced font.  For example:

@example
The only word containing the letters <samp>mt</samp> is dreamt.
@end example


@node Strong Emphasis;  STRONG,Variable;  VAR,Sample;  SAMP,Idiomatic Elements
@subsubsection Strong Emphasis:  STRONG

The @emph{STRONG} element indicates strong emphasis,
typically rendered in bold.  For example:

@example
<strong>STOP</strong>, or I'll say "<strong>STOP</strong>" again!
@end example


@node Variable;  VAR,,Strong Emphasis;  STRONG,Idiomatic Elements
@subsubsection Variable:  VAR

The @emph{VAR} element indicates a placeholder variable, typically rendered
as italic.  For example:

@example
Type <SAMP>html-check <VAR>file</VAR> | more</SAMP>
to check <VAR>file</VAR> for markup errors.
@end example


@node Typographic Elements,Anchor;  A,Idiomatic Elements,Phrase Markup
@subsection Typographic Elements

Typographic elements are used to specify the format of marked text.

Typical renderings for idiomatic elements may vary between user
agents.  If a specific rendering is necessary --- for example, when
referring to a specific text attribute as in ``The italic parts are
mandatory'' --- a typographic element can be used to ensure that the
intended typography is used where possible.

@footnote{User agents may support some typographic elements not included in
this specification, as they have been deployed to some extent.  The
@emph{STRIKE} element indicates horizontal line through the characters,
and the @emph{U} element indicates an underline.}


@menu
* Bold;  B::     Bold:  B
* Italic;  I::     Italic:  I
* Teletype;  TT::     Teletype:  TT
@end menu
@node Bold;  B,Italic;  I,Typographic Elements,Typographic Elements
@subsubsection Bold:  B

The @emph{B} element indicates bold text.  Where bold typography is
unavailable, an alternative representation may be used.


@node Italic;  I,Teletype;  TT,Bold;  B,Typographic Elements
@subsubsection Italic:  I

The @emph{I} element indicates italic text.  Where italic typography
is unavailable, an alternative representation may be used.


@node Teletype;  TT,,Italic;  I,Typographic Elements
@subsubsection Teletype:  TT

The @emph{TT} element indicates teletype (monospaced )text.  Where a
teletype font is unavailable, an alternative representation may be
used.


@node Anchor;  A,,Typographic Elements,Phrase Markup
@subsection Anchor:  A

The @emph{A} element indicates a hyperlink anchor (see @ref{Hyperlinks}).  At least one of the @emph{NAME} and @emph{HREF}
attributes should be present.  Attributes of the @emph{A} element:

@table @emph
@item HREF
gives the URI of the head anchor of a hyperlink.

@item NAME
gives the name of the anchor, and makes it available as
a head of a hyperlink.

@item TITLE
suggests a title for the destination resource ---
advisory only.  The @emph{TITLE} attribute may be used:

@itemize @bullet
@item
for display prior to accessing the destination resource, for
example, as a margin note or on a small box while the mouse is over
the anchor, or while the document is being loaded;

@item
for resources that do not include a title, such as graphics, plain
text and Gopher menus, for use as a window title.
@end itemize

@item REL
The @emph{REL} attribute gives the relationship(s) described
by the hyperlink.  The value is a whitespace separated list of
relationship names.  The semantics of link relationships are not
specified in this document.

@item REV
same as the REL attribute, but the semantics of the
relationship 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
specifies a preferred, more persistent identifier for the
head anchor of the hyperlink.  The syntax and semantics of the
@emph{URN} attribute are not yet specified.

@item METHODS
specifies methods to be used in accessing the
destination, as a whitespace-separated list of names.  The set of
applicable names is a function of the scheme of the URI in the
@emph{HREF} attribute.  For similar reasons as for the TITLE attribute,
it may be useful to include the information in advance in the
link.  For example, the HTML user agent may chose a different rendering
as a function of the methods allowed;  for example, something that is
searchable may get a different icon.

@noindent
@end table


@node Line Break;  BR,Horizontal Rule;  HR,Phrase Markup,Document Structure
@section Line Break:  BR

The @emph{BR} element specifies a line break between words (see
@ref{Characters; Words; and Paragraphs}).  For example:

@example
<P> Pease porridge hot<BR>
Pease porridge cold<BR>
Pease porridge in the pot<BR>
Nine days old.
@end example


@node Horizontal Rule;  HR,Image;  IMG,Line Break;  BR,Document Structure
@section Horizontal Rule:  HR

The @emph{HR} element is a divider between sections of text;
typically a full width horizontal rule or equivalent graphic.  For
example:

@example
<HR>
<ADDRESS>February 8, 1995, CERN</ADDRESS>
</BODY>
@end example


@node Image;  IMG,,Horizontal Rule;  HR,Document Structure
@section Image:  IMG

The @emph{IMG} element refers to an image or icon via a hyperlink
(see @ref{Simultaneous Presentation of Image Resources}).

HTML user agents may process the value of the @emph{ALT} attribute
as an alternative to processing the image resource indicated by the
@emph{SRC} attribute.
@footnote{Some HTML user agents can process graphics linked via anchors,
but not @emph{IMG} graphics.  If a graphic is essential, it should be
referenced from an @emph{A} element rather than an @emph{IMG} element.  If
the graphic is not essential, then the @emph{IMG} element is
appropriate.}

Attributes of the @emph{IMG} element:

@table @emph
@item ALIGN
alignment of the image with respect to the text
baseline.

@itemize @bullet
@item
@samp{TOP} specifies that the top of the image aligns with the
tallest item on the line containing the image.

@item
@samp{MIDDLE} specifies that the center of the image aligns with
the baseline of the line containing the image.

@item
@samp{BOTTOM} specifies that the bottom of the image aligns with
the baseline of the line containing the image.
@end itemize

@item ALT
text to use in place of the referenced image resource, for
example due to processing constraints or user preference.

@item ISMAP
indicates an image map (see @ref{Image Maps}).

@item SRC
specifies the URI of the image resource.
@footnote{In practice, the media types of image resources are limited to a
few raster graphic formats:  typically @samp{image/gif},
@samp{image/jpeg}.  In particular, @samp{text/html}
resources are not intended to be used as image resources.}

@noindent
@end table

Examples of use:

@example
<IMG SRC="triangle.xbm" ALT="Warning:"> Be sure 
to read these instructions.
@end example

@example
<a href="http://machine/htbin/imagemap/sample">
<IMG SRC="sample.xbm" ISMAP>
</a>
@end example


@node Characters; Words; and Paragraphs,Hyperlinks,Document Structure,Top
@chapter Characters, Words, and Paragraphs
An HTML user agent should present the body of an HTML document as a
collection of typeset paragraphs and preformatted text.  Except for
preformatted elements (@emph{PRE}, @emph{XMP}, @emph{LISTING},
@emph{TEXTAREA}), each block structuring element is regarded as a
paragraph by taking the data characters in its content and the content
of its descendant elements, concatenating them, and splitting the
result into words, separated by space, tab, or record end characters
(and perhaps hyphen characters).  The sequence of words is typeset as a
paragraph by breaking it into lines.


@menu
* The HTML Document Character Set::
@end menu
@node The HTML Document Character Set,,Characters; Words; and Paragraphs,Characters; Words; and Paragraphs
@section The HTML Document Character Set
The document character set specified in @ref{SGML Declaration for HTML} must be
supported by HTML user agents.  It includes the graphic characters of
Latin Alphabet No.  1, or simply Latin-1.  Latin-1 comprises 191
graphic characters, including the alphabets of most Western European
languages.
@footnote{Use of the non-breaking space and soft hyphen indicator characters is 
discouraged because support for them is not widely deployed.}
@footnote{To support non-western writing systems, a larger character repertoire
will be specified in a future version of HTML@.  The document character
set will be [ISO-10646], or some subset that agrees with [ISO-10646];
in particular, all numeric character references must use code
positions assigned by [ISO-10646].}

In SGML applications, the use of control characters is limited in
order to maximize the chance of successful interchange over
heterogeneous networks and operating systems.  In the HTML document
character set only three control characters are allowed:  Horizontal
Tab, Carriage Return, and Line Feed (code positions 9, 13, and 10).

The HTML DTD references the Added Latin 1 entity set, to allow
mnemonic representation of selected Latin 1 characters using only the
widely supported ASCII character repertoire.  For example:

@example
Kurt G&ouml;del was a famous logician and mathematician.
@end example

See @ref{ISO Latin 1 Character Entity Set} for a table of the ``Added Latin 1''
entities, and @ref{The HTML Coded Character Set} for a table of the code
positions of [ISO 8859-1] and the control characters in the HTML
document character set.


@node Hyperlinks,Forms,Characters; Words; and Paragraphs,Top
@chapter Hyperlinks

In addition to general purpose elements such as paragraphs and
lists, HTML documents can express hyperlinks.  An HTML user agent
allows the user to navigate these hyperlinks.

A hyperlink is a relationship between two anchors, called the head
and the tail of the hyperlink[DEXTER].  Anchors are identified
by an anchor address:  an absolute Uniform Resource Identifier (URI),
optionally followed by a '#' and a sequence of characters called a
fragment identifier.  For example:

@example
http://www.w3.org/hypertext/WWW/TheProject.html
http://www.w3.org/hypertext/WWW/TheProject.html#z31
@end example

In an anchor address, the URI refers to a resource;  it may be used
in a variety of information retrieval protocols to obtain an entity
that represents the resource, such as an HTML document.  The fragment
identifier, if present, refers to some view on, or portion of the
resource.

Each of the following markup constructs indicates the tail anchor
of a hyperlink or set of hyperlinks:

@itemize @bullet
@item
@emph{A} elements with @emph{HREF} present.
@item
@emph{LINK} elements.
@item
@emph{IMG} elements.
@item
@emph{INPUT} elements with the @emph{SRC} attribute present.
@item
@emph{ISINDEX} elements.
@item
@emph{FORM} elements with @samp{METHOD=GET}.
@end itemize

These markup constructs refer to head anchors by a URI, either
absolute or relative, or a fragment identifier, or both.

In the case of a relative URI, the absolute URI in the address of
the head anchor is the result of combining the relative URI with a
base absolute URI as in [RELURL].  The base document is taken from the
document's @emph{BASE} element, if present;  else, it is determined as
in [RELURL].


@menu
* Accessing Resources::
* Activation of Hyperlinks::
* Simultaneous Presentation of Image Resources::
* Fragment Identifiers::
* Queries and Indexes::
* Image Maps::
@end menu
@node Accessing Resources,Activation of Hyperlinks,Hyperlinks,Hyperlinks
@section Accessing Resources

Once the address of the head anchor is determined, the user agent
may obtain a representation of the resource.

For example, if the base URI is @samp{http://host/x/y.html} and
the document contains:

@example
<img src="../icons/abc.gif">
@end example

then the user agent uses the URI
@samp{http://host/icons/abc.gif} to access the resource, as in
[URL]..


@node Activation of Hyperlinks,Simultaneous Presentation of Image Resources,Accessing Resources,Hyperlinks
@section Activation of Hyperlinks

An HTML user agent allows the user to navigate the content of the
document and request activation of hyperlinks denoted by @emph{A}
elements.  HTML user agents should also allow activation of @emph{LINK}
element hyperlinks.

To activate a link, the user agent obtains a representation of the
resource identified in the address of the head anchor.  If the
representation is another HTML document, navigation may begin again
with this new document.


@node Simultaneous Presentation of Image Resources,Fragment Identifiers,Activation of Hyperlinks,Hyperlinks
@section Simultaneous Presentation of Image Resources
An HTML user agent may activate hyperlinks indicated by @emph{IMG} and
@emph{INPUT} elements concurrently with processing the document;  that
is, image hyperlinks may be processed without explicit request by the
user.  Image resources should be embedded in the presentation at the
point of the tail anchor, that is the @emph{IMG} or @emph{INPUT} element.

@emph{LINK} hyperlinks may also be processed without explicit user
request;  for example, style sheet resources may be processed before or
during the processing of the document.


@node Fragment Identifiers,Queries and Indexes,Simultaneous Presentation of Image Resources,Hyperlinks
@section Fragment Identifiers
Any characters following a @samp{#} character in a hypertext address
constitute a fragment identifier.  In particular, an address of
the form @samp{#fragment} refers to an anchor in the same document.

The meaning of fragment identifiers depends on the media type of the
representation of the anchor's resource.  For @samp{text/html}
representations, it refers to the @emph{A} element with a @emph{NAME}
attribute whose value is the same as the fragment identifier.  The
matching is case sensitive.  The document should have exactly one such
element.  The user agent should indicate the anchor element, for
example by scrolling to and/or highlighting the phrase.

For example, if the base URI is @samp{http://host/x/y.html} and the
user activated the link denoted by the following markup:

@example
<p> See: <a href="app1.html#bananas">appendix 1</a> 
for more detail on bananas.
@end example

Then the user agent accesses the resource identified by
@samp{http://host/x/app1.html}.  Assuming the resource is represented
using the @samp{text/html} media type, the user agent must locate
the @emph{A} element whose @emph{NAME} attribute is @samp{bananas}
and begin navigation there.


@node Queries and Indexes,Image Maps,Fragment Identifiers,Hyperlinks
@section Queries and Indexes

The @emph{ISINDEX} element represents a set of hyperlinks.  The user
can choose from the set by providing keywords to the user agent.  The
user agent computes the head URI by appending @samp{?} and the
keywords to the base URI@.  The keywords are escaped according to [URL]
and joined by @samp{+}.  For example, if a document contains:

@example
<BASE HREF="http://host/index">
<ISINDEX>
@end example

and the user provides the keywords @samp{apple} and @samp{berry},
then the user agent must access the resource
@samp{http://host/index?apple+berry}.

@emph{FORM} elements with @samp{METHOD=GET} also represent sets of
hyperlinks.  See @ref{Query Forms;  METHOD=GET} for details.


@node Image Maps,,Queries and Indexes,Hyperlinks
@section Image Maps

If the @emph{ISMAP} attribute is present on an @emph{IMG} element,
the @emph{IMG} element must be contained in an @emph{A} element with an
@emph{HREF} present.  This construct represents a set of
hyperlinks.  The user can choose from the set by choosing a pixel of
the image.  The user agent computes the head URI by appending @samp{?}
and the x and y coordinates of the pixel to the URI given in the
@emph{A} element.  For example, if a document contains:

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<head><title>ImageMap Example</title>
<BASE HREF="http://host/index"></head>
<body>
<p> Choose any of these icons:<br>
<a href="/cgi-bin/imagemap"><img ismap src="icons.gif"></a>
@end example

and the user chooses the upper-leftmost pixel, the chosen
hyperlink is the one with the URI
@samp{http://host/cgi-bin/imagemap?0,0}.


@node Forms,HTML Public Text,Hyperlinks,Top
@chapter Forms

A form is a template for a form data set and an associated method
and action URI@.  A form data set is a sequence of name/value pair
fields.  The names are specified on the @emph{NAME} attributes of form
input elements, and the values are given initial values by various
forms of markup and edited by the user.  The resulting form data set is
used to access an information service as a function of the action and
method.

Forms elements can be mixed in with document structuring
elements.  For example, a @emph{PRE} element may contain a @emph{FORM}
element, or a @emph{FORM} element may contain lists which contain
@emph{INPUT} elements.  This gives considerable flexibility in
designing the layout of forms.

Form processing is a level 2 feature.


@menu
* Form Elements::
* Form Submission::
@end menu
@node Form Elements,Form Submission,Forms,Forms
@section Form Elements

@menu
* Form;  FORM::     Form:  FORM
* Input Field;  INPUT::     Input Field:  INPUT
* Selection;  SELECT::     Selection:  SELECT
* Text Area;  TEXTAREA::     Text Area:  TEXTAREA
@end menu
@node Form;  FORM,Input Field;  INPUT,Form Elements,Form Elements
@subsection Form:  FORM

The @emph{FORM} element contains a sequence of input elements, along
with document structuring elements.  The attributes are:

@table @emph
@item ACTION
specifies the action URI for the form.  The action URI of
a form defaults to the base URI of the document (see @ref{Hyperlinks}).

@item METHOD
selects a method of accessing the action URI@.  The set of
applicable methods is a function of the scheme of the action URI of
the form.  See @ref{Query Forms;  METHOD=GET} and @ref{Forms with Side-Effects;  METHOD=POST}.

@item ENCTYPE
specifies the media type used to encode the name/value
pairs for transport, in case the protocol does not itself impose a
format.  See @ref{The form-urlencoded Media Type}.

@end table


@node Input Field;  INPUT,Selection;  SELECT,Form;  FORM,Form Elements
@subsection Input Field:  INPUT

The @emph{INPUT} element represents a field for user input.  The
@emph{TYPE} attribute discriminates between several variations of
fields.

The @emph{INPUT} element has a number of attributes.  The set of
applicable attributes depends on the value of the @emph{TYPE}
attribute.  


@menu
* Text Field;  INPUT TYPE=TEXT::     Text Field:  INPUT TYPE=TEXT
* Password Field;  INPUT TYPE=PASSWORD::     Password Field:  INPUT TYPE=PASSWORD
* Check Box;  INPUT TYPE=CHECKBOX::     Check Box:  INPUT TYPE=CHECKBOX
* Radio Button;  INPUT TYPE=RADIO::     Radio Button:  INPUT TYPE=RADIO
* Image Pixel;  INPUT TYPE=IMAGE::     Image Pixel:  INPUT TYPE=IMAGE
* Hidden Field;  INPUT TYPE=HIDDEN::     Hidden Field:  INPUT TYPE=HIDDEN
* Submit Button;  INPUT TYPE=SUBMIT::     Submit Button:  INPUT TYPE=SUBMIT
* Reset Button;  INPUT TYPE=RESET::     Reset Button:  INPUT TYPE=RESET
@end menu
@node Text Field;  INPUT TYPE=TEXT,Password Field;  INPUT TYPE=PASSWORD,Input Field;  INPUT,Input Field;  INPUT
@subsubsection Text Field:  INPUT TYPE=TEXT

The default vaule of the @emph{TYPE} attribute is @samp{TEXT},
indicating a single line text entry field.  (Use the @emph{TEXTAREA}
element for multi-line text fields.)

Required attributes are:

@table @emph
@item NAME
name for the form field corresponding to this
element.

@noindent
@end table

The optional attributes are:

@table @emph
@item MAXLENGTH
constrains the number of characters that can be
entered into a text input field.  If the value of @emph{MAXLENGTH} is
greater the the value of the @emph{SIZE} attribute, the field should
scroll appropriately.  The default number of characters is unlimited.

@item SIZE
specifies the amount of display space allocated to this
input field according to its type.  The default depends on the user
agent.

@item VALUE
The initial value of the field.

@noindent
@end table

For example:

@example
<p>Street Address: <input name=street><br>
Postal City code: <input name=city size=16 maxlength=16><br>
Zip Code: <input name=zip size=10 maxlength=10 value="99999-9999"><br>
@end example


@node Password Field;  INPUT TYPE=PASSWORD,Check Box;  INPUT TYPE=CHECKBOX,Text Field;  INPUT TYPE=TEXT,Input Field;  INPUT
@subsubsection Password Field:  INPUT TYPE=PASSWORD
An @emph{INPUT} element with @samp{TYPE=PASSWORD} is a text field as
above, except that the value is obscured as it is entered.  (see also:
@ref{Security Considerations}).

For example:

@example
<p>Name: <input name=login> Password: <input type=password name=passwd>
@end example


@node Check Box;  INPUT TYPE=CHECKBOX,Radio Button;  INPUT TYPE=RADIO,Password Field;  INPUT TYPE=PASSWORD,Input Field;  INPUT
@subsubsection Check Box:  INPUT TYPE=CHECKBOX

An @emph{INPUT} element with @samp{TYPE=CHECKBOX} represents a
boolean choice.  A set of such elements with the same name represents
an n-of-many choice field.  Required attributes are:

@table @emph
@item NAME
symbolic name for the form field corresponding to this
element or group of elements.

@item VALUE
The portion of the value of the field contributed by this
element.

@noindent
@end table

Optional attributes are:

@table @emph
@item CHECKED
indicates that the initial state is on.

@noindent
@end table

For example:

@example
<p>What flavors do you like?
<input type=checkbox name=flavor value=vanilla>Vanilla<br>
<input type=checkbox name=flavor value=strawberry>Strawberry<br>
<input type=checkbox name=flavor value=chocolate checked>Chocolate<br>
@end example


@node Radio Button;  INPUT TYPE=RADIO,Image Pixel;  INPUT TYPE=IMAGE,Check Box;  INPUT TYPE=CHECKBOX,Input Field;  INPUT
@subsubsection Radio Button:  INPUT TYPE=RADIO

An @emph{INPUT} element with @samp{TYPE=RADIO} represents a boolean
choice.  A set of such elements with the same name represents a
1-of-many choice field.  The @emph{NAME} and @emph{VALUE} attributes
are required as for check boxes.  Optional attributes are:

@table @emph
@item CHECKED
indicates that the initial state is on.

@noindent
@end table

At all times, exactly one of the radio buttons in a set is
checked.  If none of the @emph{INPUT} elements of a set of radio buttons
specifies @samp{CHECKED}, then the user agent must check the first
radio button of the set initially.

For example:

@example
<p>Which is your favorite?
<input type=radio name=flavor value=vanilla>Vanilla<br>
<input type=radio name=flavor value=strawberry>Strawberry<br>
<input type=radio name=flavor value=chocolate>Chocolate<br>
@end example


@node Image Pixel;  INPUT TYPE=IMAGE,Hidden Field;  INPUT TYPE=HIDDEN,Radio Button;  INPUT TYPE=RADIO,Input Field;  INPUT
@subsubsection Image Pixel:  INPUT TYPE=IMAGE

An @emph{INPUT} element with @samp{TYPE=IMAGE} specifies an image
resource to display, and allows input of two form fields:  the x and y
coordinate of a pixel chosen from the image.  The names of the fields
are the name of the field with @samp{.x} and @samp{.y}
appended.  @samp{TYPE=IMAGE} implies @samp{TYPE=SUBMIT} processing;
that is, when a pixel is chosen, the form as a whole is submitted.

The @emph{NAME} attribute is required as for other input
fields.  The @emph{SRC} attribute is required and the @emph{ALIGN} is
optional as for the @emph{IMG} element (see @ref{Image;  IMG}).

For example:

@example
<p>Choose a point on the map:
<input type=image name=point src="map.gif">
@end example


@node Hidden Field;  INPUT TYPE=HIDDEN,Submit Button;  INPUT TYPE=SUBMIT,Image Pixel;  INPUT TYPE=IMAGE,Input Field;  INPUT
@subsubsection Hidden Field:  INPUT TYPE=HIDDEN

An @emph{INPUT} element with @samp{TYPE=HIDDEN} represents a hidden
field.The user does not interact with this field;  instead, the
@emph{VALUE} attribute specifies the value of the field.  The
@emph{NAME} and @emph{VALUE} attributes are required.

For example:

@example
<input type=hidden name=context value="l2k3j4l2k3j4l2k3j4lk23">
@end example


@node Submit Button;  INPUT TYPE=SUBMIT,Reset Button;  INPUT TYPE=RESET,Hidden Field;  INPUT TYPE=HIDDEN,Input Field;  INPUT
@subsubsection Submit Button:  INPUT TYPE=SUBMIT
An @emph{INPUT} element with @samp{TYPE=SUBMIT} represents an input
option, typically a button, that instructs the user agent to submit
the form.  Optional attributes are:

@table @emph
@item NAME
indicates that this element contributes a form field whose
value is given by the @emph{VALUE} attribute.  If the @emph{NAME}
attribute is not present, this element does not contribute a form
field.

@item VALUE
indicates a label
for the input (button).

@noindent
@end table

@example
You may submit this request internally:
<input type=submit name=recipient value=internal><br>
or to the external world:
<input type=submit name=recipient value=world>
@end example


@node Reset Button;  INPUT TYPE=RESET,,Submit Button;  INPUT TYPE=SUBMIT,Input Field;  INPUT
@subsubsection Reset Button:  INPUT TYPE=RESET
An @emph{INPUT} element with @samp{TYPE=RESET} represents an input
option, typically a button, that instructs the user agent to reset the
form's fields to their initial states.  The @emph{VALUE} attribute, if
present, indicates a label for the input (button).

@example
When you are finished, you may submit this request:
<input type=submit><br>
You may clear the form and start over at any time: <input type=reset>
@end example


@node Selection;  SELECT,Text Area;  TEXTAREA,Input Field;  INPUT,Form Elements
@subsection Selection:  SELECT

The @emph{SELECT} element constrains the form field to an enumerated
list of values.  The values are given in @emph{OPTION} elements.
Attributes are:

@table @emph
@item MULTIPLE
indicates that more than one option may be included in
the value.

@item NAME
specifies the name of the form field.

@item SIZE
specifies the number of visible items.  Select fields of
size one are typically pop-down menus, whereas select fields with size
greater than one are typically lists.

@end table

For example:

@example
<SELECT NAME="flavor">
<OPTION>Vanilla
<OPTION>Strawberry
<OPTION value="RumRasin">Rum and Raisin
<OPTION selected>Peach and Orange
</SELECT>
@end example

The initial state has the first option selected, unless a
@emph{SELECTED} attribute is present on any of the @emph{OPTION}
elements.


@menu
* Option;  OPTION::     Option:  OPTION
@end menu
@node Option;  OPTION,,Selection;  SELECT,Selection;  SELECT
@subsubsection Option:  OPTION

The Option element can only occur within a Select element.  It
represents one choice, and has the following attributes:

@table @emph
@item SELECTED
Indicates that this option is initially selected.

@item VALUE
indicates the value to be returned if this
option is chosen.  The field value defaults to the content of the
@emph{OPTION} element.

@noindent
@end table

The content of the @emph{OPTION} element is presented to the user to
represent the option.  It is used as a returned value if the VALUE
attribute is not present.


@node Text Area;  TEXTAREA,,Selection;  SELECT,Form Elements
@subsection Text Area:  TEXTAREA

The @emph{TEXTAREA} element represents a multi-line text
field.  Attributes are:

@table @emph
@item COLS
the number of visible columns to display for the text area,
in characters.
@item NAME
Specifies the name of the form field.
@item ROWS
The number of visible rows to display for the text area, in
characters.

@noindent
@end table

For example:

@example
<TEXTAREA NAME="address" ROWS=6 COLS=64>
HaL Computer Systems
1315 Dell Avenue
Campbell, California 95008
</TEXTAREA>
@end example

The content of the @emph{TEXTAREA} element is the field's initial
value.

Typically, the ROWS and COLS attributes determine the visible
dimension of the field in characters.  The field is typically rendered
in a fixed-width font.  HTML user agents should allow text to extend
beyond these limits by scrolling as needed.


@node Form Submission,,Form Elements,Forms
@section Form Submission

An HTML user agent begins processing a form by presenting the
document with the fields in their initial state.  The user is allowed
to modify the fields, constrained by the field type etc.  When the user
indicates that the form should be submitted (using a submit button or
image input), the form data set is processed according to its method,
action URI and enctype.

When there is only one single-line text input field in a form, the
user agent should accept Enter in that field as a request to submit
the form.


@menu
* The form-urlencoded Media Type::
* Query Forms;  METHOD=GET::     Query Forms:  METHOD=GET
* Forms with Side-Effects;  METHOD=POST::     Forms with Side-Effects:  METHOD=POST
* Example Form Submission;  Questionnaire Form::     Example Form Submission:  Questionnaire Form
@end menu
@node The form-urlencoded Media Type,Query Forms;  METHOD=GET,Form Submission,Form Submission
@subsection The form-urlencoded Media Type

The default encoding for all forms is
@samp{application/x-www-form-urlencoded}.  A form data set is
represented in this media type as follows:

@enumerate
@item
The form field names and values are escaped:  space characters are
replaced by @samp{+}, and then reserved characters are escaped as per
[URL];  that is, non-alphanumeric characters are replaced by
@samp{%HH}, a percent sign and two hexadecimal digits representing the
ASCII code of the character.  Line breaks, as in multi-line text field
values, are represented as CR LF pairs, i.e.  @samp{%0D%0A}.

@item
The fields are listed in the order they appear in the document
with the name separated from the value by @samp{=} and the pairs
separated from each other by @samp{&}.  Fields with null values may be
omitted.  In particular, unselected radio buttons and checkboxes should
not appear in the encoded data, but hidden fields with @emph{VALUE}
attributes present should.
@footnote{The URI from a query form submission can be used in a normal
anchor style hyperlink.  Unfortunately, the use of the @samp{&}
character to separate form fields interacts with its use in SGML
attribute values as an entity reference delimiter.  For example, the
URI @samp{http://host/?x=1&y=2} must be written
@samp{<a href="http://host/?x=1&#38;y=2"} or
@samp{<a href="http://host/?x=1&amp;y=2">}.

HTTP server implementors, and in particular, CGI implementors are
encouraged to support the use of @samp{;} in place of @samp{&} to save
users the trouble of escaping @samp{&} characters this way.}
@end enumerate


@node Query Forms;  METHOD=GET,Forms with Side-Effects;  METHOD=POST,The form-urlencoded Media Type,Form Submission
@subsection Query Forms:  METHOD=GET

If the processing of a form is idempotent (i.e.  it has no lasting
observable effect on the state of the world), then the form method
should be @samp{GET}.  Many database searches have no visible
side-effects and make ideal applications of query forms.

To process a form whose action URL is an HTTP URL and whose method
is @samp{GET}, the user agent starts with the action URI and appends a
@samp{?} and the form data set, in
@samp{application/x-www-form-urlencoded} format as above.  The user
agent then traverses the link to this URI just as if it were an anchor
(see @ref{Activation of Hyperlinks}).
@footnote{The URL encoding may result in very long URIs, which cause some
historical HTTP server implementations to exhibit defective behavior.
As a result, some HTML forms are written using @samp{METHOD=POST} even
though the form submission has no side-effects.}


@node Forms with Side-Effects;  METHOD=POST,Example Form Submission;  Questionnaire Form,Query Forms;  METHOD=GET,Form Submission
@subsection Forms with Side-Effects:  METHOD=POST

If the service associated with the processing of a form has side
effects (for example, modification of a database or subscription to a
service), the method should be @samp{POST}.

To process a form whose action URL is an HTTP URL and whose method
is @samp{POST}, the user agent conducts an HTTP POST transaction using
the action URI, and a message body of type
@samp{application/x-www-form-urlencoded} format as above.  The user
agent should display the response from the HTTP POST interaction just
as it would display the response from an HTTP GET above.


@node Example Form Submission;  Questionnaire Form,,Forms with Side-Effects;  METHOD=POST,Form Submission
@subsection Example Form Submission:  Questionnaire Form

Consider the following document:

@example
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<title>Sample of HTML Form Submission</title>
<H1>Sample Questionnaire</H1>
<P>Please fill out this questionnaire:
<FORM METHOD="POST" ACTION="http://www.w3.org/sample">
<P>Your name: <INPUT NAME="name" size="48">
<P>Male <INPUT NAME="gender" TYPE=RADIO VALUE="male">
<P>Female <INPUT NAME="gender" TYPE=RADIO VALUE="female">
<P>Number in family: <INPUT NAME="family" TYPE=text>
<P>Cities in which you maintain a residence:
<UL>
<LI>Kent <INPUT NAME="city" TYPE=checkbox VALUE="kent">
<LI>Miami <INPUT NAME="city" TYPE=checkbox VALUE="miami">
<LI>Other <TEXTAREA NAME="other" cols=48 rows=4></textarea>
</UL>
Nickname: <INPUT NAME="nickname" SIZE="42">
<P>Thank you for responding to this questionnaire.
<P><INPUT TYPE=SUBMIT> <INPUT TYPE=RESET>
</FORM>
@end example

The initial state of the form data set is:

@table @emph
@item name
``''
@item gender
``male''
@item family
``''
@item other
``''
@item nickname
``''

@noindent
@end table

Note that the radio input has an initial value, while the checkbox
has none.

The user might edit the fields and request that the form be
submitted.  At that point, suppose the values are:

@table @emph
@item name
``John Doe''
@item gender
``male''
@item family
``5''
@item city
``kent''
@item city
``miami''
@item other
``abc\ndef''
@item nickname
``J&D''

@noindent
@end table

The user agent then conducts an HTTP POST transaction using the URI
@samp{http://www.w3.org/sample}.  The message body would be (ignore
the line break):

@example
name=John+Doe&gender=male&family=5&city=kent&city=miami&
other=abc%0D%0Adef&nickname=J%26D
@end example


@node HTML Public Text,Security Considerations,Forms,Top
@chapter HTML Public Text

@menu
* HTML DTD::
* Strict HTML DTD::
* Level 1 HTML DTD::
* Strict Level 1 HTML DTD::
* SGML Declaration for HTML::
* Sample SGML Open Entity Catalog for HTML::
* Character Entity Sets::
@end menu
@node HTML DTD,Strict HTML DTD,HTML Public Text,HTML Public Text
@section HTML DTD

This is the Document Type Definition for the HyperText Markup
Language, level 2.

@example
<!--    html.dtd
        Document Type Definition for the HyperText Markup Language               
 (HTML DTD)        
$Id: html.dtd,v 1.30 1995/09/21 23:30:19 connolly Exp $        
Author: Daniel W. Connolly <connolly@@w3.org>        
See Also: html.decl, html-1.dtd        
  http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
-->
<!ENTITY % HTML.Version
        "-//IETF//DTD HTML 2.0//EN"
        -- Typical usage:
            <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
            <html>
            ...
            </html>
        --
        >
<!--============ Feature Test Entities ========================-->
<!ENTITY % HTML.Recommended "IGNORE"        
-- Certain features of the language are necessary for        
   compatibility with widespread usage, but they may        
   compromise the structural integrity of a document.        
   This feature test entity enables a more prescriptive        
   document type definition that eliminates        
   those features.        
-->
<![ %HTML.Recommended [
        <!ENTITY % HTML.Deprecated "IGNORE">
]]>
<!ENTITY % HTML.Deprecated "INCLUDE"        
-- Certain features of the language are necessary for        
   compatibility with earlier versions of the specification,        
   but they tend to be used and implemented inconsistently,        
   and their use is deprecated. This feature test entity        
   enables a document type definition that eliminates        
   these features.        
-->
<!ENTITY % HTML.Highlighting "INCLUDE"        
-- Use this feature test entity to validate that a        
   document uses no highlighting tags, which may be        
   ignored on minimal implementations.        
-->
<!ENTITY % HTML.Forms "INCLUDE"
        -- Use this feature test entity to validate that a document
           contains no forms, which may not be supported in minimal
           implementations
        -->
<!--============== Imported Names ==============================-->
<!ENTITY % Content-Type "CDATA"
        -- meaning an internet media type
           (aka MIME content type, as per RFC1521)
        -->
<!ENTITY % HTTP-Method "GET | POST"
        -- as per HTTP specification, in progress
        -->
<!--========= DTD "Macros" =====================-->
<!ENTITY % heading "H1|H2|H3|H4|H5|H6">
<!ENTITY % list " UL | OL | DIR | MENU " >
<!--======= Character mnemonic entities =================-->
<!ENTITY % ISOlat1 PUBLIC
  "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
%ISOlat1;
<!ENTITY amp CDATA "&#38;"     -- ampersand          -->
<!ENTITY gt CDATA "&#62;"      -- greater than       -->
<!ENTITY lt CDATA "&#60;"      -- less than          -->
<!ENTITY quot CDATA "&#34;"    -- double quote       -->
<!--========= SGML Document Access (SDA) Parameter Entities =====-->
<!-- HTML 2.0 contains SGML Document Access (SDA) fixed attributes
in support of easy transformation to the International Committee
for Accessible Document Design (ICADD) DTD        
 "-//EC-USA-CDA/ICADD//DTD ICADD22//EN".
ICADD applications are designed to support usable access to
structured information by print-impaired individuals through
Braille, large print and voice synthesis.  For more information on
SDA & ICADD:  
        - ISO 12083:1993, Annex A.8, Facilities for Braille,        
  large print and computer voice
        - ICADD ListServ        
  <ICADD%ASUACAD.BITNET@@ARIZVM1.ccit.arizona.edu>
        - Usenet news group bit.listserv.easi
        - Recording for the Blind, +1 800 221 4792
-->
<!ENTITY % SDAFORM  "SDAFORM  CDATA  #FIXED"        
  -- one to one mapping        -->
<!ENTITY % SDARULE  "SDARULE  CDATA  #FIXED"        
  -- context-sensitive mapping -->
<!ENTITY % SDAPREF  "SDAPREF  CDATA  #FIXED"        
  -- generated text prefix     -->
<!ENTITY % SDASUFF  "SDASUFF  CDATA  #FIXED"        
  -- generated text suffix     -->
<!ENTITY % SDASUSP  "SDASUSP  NAME   #FIXED"        
  -- suspend transform process -->
<!--========== Text Markup =====================-->
<![ %HTML.Highlighting [
<!ENTITY % font " TT | B | I ">
<!ENTITY % phrase "EM | STRONG | CODE | SAMP | KBD | VAR | CITE ">
<!ENTITY % text "#PCDATA | A | IMG | BR | %phrase | %font">
<!ELEMENT (%font;|%phrase) - - (%text)*>
<!ATTLIST ( TT | CODE | SAMP | KBD | VAR )
        %SDAFORM; "Lit"
        >
<!ATTLIST ( B | STRONG )
        %SDAFORM; "B"
        >
<!ATTLIST ( I | EM | CITE )
        %SDAFORM; "It"
        >
<!-- <TT>       Typewriter text                         -->
<!-- <B>        Bold text                               -->
<!-- <I>        Italic text                             -->
<!-- <EM>       Emphasized phrase                       -->
<!-- <STRONG>   Strong emphasis                         -->
<!-- <CODE>     Source code phrase                      -->
<!-- <SAMP>     Sample text or characters               -->
<!-- <KBD>      Keyboard phrase, e.g. user input        -->
<!-- <VAR>      Variable phrase or substitutable        -->
<!-- <CITE>     Name or title of cited work             -->
<!ENTITY % pre.content "#PCDATA | A | HR | BR | %font | %phrase">
]]>
<!ENTITY % text "#PCDATA | A | IMG | BR">
<!ELEMENT BR    - O EMPTY>
<!ATTLIST BR
        %SDAPREF; "&#RE;"
        >
<!-- <BR>       Line break      -->
<!--========= Link Markup ======================-->
<!ENTITY % linkType "NAMES">
<!ENTITY % linkExtraAttributes
        "REL %linkType #IMPLIED
        REV %linkType #IMPLIED
        URN CDATA #IMPLIED
        TITLE CDATA #IMPLIED
        METHODS NAMES #IMPLIED
        ">
<![ %HTML.Recommended [
        <!ENTITY % A.content   "(%text)*"
        -- <H1><a name="xxx">Heading</a></H1>
                is preferred to
           <a name="xxx"><H1>Heading</H1></a>
        -->
]]>
<!ENTITY % A.content   "(%heading|%text)*">
<!ELEMENT A     - - %A.content -(A)>
<!ATTLIST A
        HREF CDATA #IMPLIED
        NAME CDATA #IMPLIED
        %linkExtraAttributes;
        %SDAPREF; "<Anchor: #AttList>"
        >
<!-- <A>               Anchor; source/destination of link    -->
<!-- <A NAME="...">     Name of this anchor                -->
<!-- <A HREF="...">     Address of link destination         -->
<!-- <A URN="...">      Permanent address of destination     -->
<!-- <A REL=...>        Relationship to destination       -->
<!-- <A REV=...>        Relationship of destination to this    -->
<!-- <A TITLE="...">    Title of destination (advisory)       -->
<!-- <A METHODS="...">  Operations on destination (advisory)     -->
<!--========== Images ==========================-->
<!ELEMENT IMG    - O EMPTY>
<!ATTLIST IMG
        SRC CDATA  #REQUIRED
        ALT CDATA #IMPLIED
        ALIGN (top|middle|bottom) #IMPLIED
        ISMAP (ISMAP) #IMPLIED
        %SDAPREF; "<Fig><?SDATrans Img: #AttList>#AttVal(Alt)</Fig>"
        >
<!-- <IMG>              Image; icon, glyph or illustration      -->
<!-- <IMG SRC="...">    Address of image object                 -->
<!-- <IMG ALT="...">    Textual alternative                     -->
<!-- <IMG ALIGN=...>    Position relative to text               -->
<!-- <IMG ISMAP>        Each pixel can be a link                -->
<!--========== Paragraphs=======================-->
<!ELEMENT P     - O (%text)*>
<!ATTLIST P
        %SDAFORM; "Para"
        >
<!-- <P>        Paragraph       -->
<!--========== Headings, Titles, Sections ===============-->
<!ELEMENT HR    - O EMPTY>
<!ATTLIST HR
        %SDAPREF; "&#RE;&#RE;"
        >
<!-- <HR>       Horizontal rule -->
<!ELEMENT ( %heading )  - -  (%text;)*>
<!ATTLIST H1
        %SDAFORM; "H1"
        >
<!ATTLIST H2
        %SDAFORM; "H2"
        >
<!ATTLIST H3
        %SDAFORM; "H3"
        >
<!ATTLIST H4
        %SDAFORM; "H4"
        >
<!ATTLIST H5
        %SDAFORM; "H5"
        >
<!ATTLIST H6
        %SDAFORM; "H6"
        >
<!-- <H1>       Heading, level 1 -->
<!-- <H2>       Heading, level 2 -->
<!-- <H3>       Heading, level 3 -->
<!-- <H4>       Heading, level 4 -->
<!-- <H5>       Heading, level 5 -->
<!-- <H6>       Heading, level 6 -->
<!--========== Text Flows ======================-->
<![ %HTML.Forms [
        <!ENTITY % block.forms "BLOCKQUOTE | FORM | ISINDEX">
]]>
<!ENTITY % block.forms "BLOCKQUOTE">
<![ %HTML.Deprecated [
        <!ENTITY % preformatted "PRE | XMP | LISTING">
]]>
<!ENTITY % preformatted "PRE">
<!ENTITY % block "P | %list | DL
        | %preformatted
        | %block.forms">
<!ENTITY % flow "(%text|%block)*">
<!ENTITY % pre.content "#PCDATA | A | HR | BR">
<!ELEMENT PRE - - (%pre.content)*>
<!ATTLIST PRE
        WIDTH NUMBER #implied
        %SDAFORM; "Lit"
        >
<!-- <PRE>              Preformatted text               -->
<!-- <PRE WIDTH=...>    Maximum characters per line     -->
<![ %HTML.Deprecated [
<!ENTITY % literal "CDATA"
        -- historical, non-conforming parsing mode where
           the only markup signal is the end tag
           in full
        -->
<!ELEMENT (XMP|LISTING) - -  %literal>
<!ATTLIST XMP
        %SDAFORM; "Lit"
        %SDAPREF; "Example:&#RE;"
        >
<!ATTLIST LISTING
        %SDAFORM; "Lit"
        %SDAPREF; "Listing:&#RE;"
        >
<!-- <XMP>              Example section         -->
<!-- <LISTING>          Computer listing        -->
<!ELEMENT PLAINTEXT - O %literal>
<!-- <PLAINTEXT>        Plain text passage      -->
<!ATTLIST PLAINTEXT
        %SDAFORM; "Lit"
        >
]]>
<!--========== Lists ==================-->
<!ELEMENT DL    - -  (DT | DD)+>
<!ATTLIST DL
        COMPACT (COMPACT) #IMPLIED
        %SDAFORM; "List"
        %SDAPREF; "Definition List:"
        >
<!ELEMENT DT    - O (%text)*>
<!ATTLIST DT
        %SDAFORM; "Term"
        >
<!ELEMENT DD    - O %flow>
<!ATTLIST DD
        %SDAFORM; "LItem"
        >
<!-- <DL>               Definition list, or glossary    -->
<!-- <DL COMPACT>       Compact style list              -->
<!-- <DT>               Term in definition list         -->
<!-- <DD>               Definition of term              -->
<!ELEMENT (OL|UL) - -  (LI)+>
<!ATTLIST OL
        COMPACT (COMPACT) #IMPLIED
        %SDAFORM; "List"
        >
<!ATTLIST UL
        COMPACT (COMPACT) #IMPLIED
        %SDAFORM; "List"
        >
<!-- <UL>               Unordered list                  -->
<!-- <UL COMPACT>       Compact list style              -->
<!-- <OL>               Ordered, or numbered list       -->
<!-- <OL COMPACT>       Compact list style              -->
<!ELEMENT (DIR|MENU) - -  (LI)+ -(%block)>
<!ATTLIST DIR
        COMPACT (COMPACT) #IMPLIED
        %SDAFORM; "List"
        %SDAPREF; "<LHead>Directory</LHead>"
        >
<!ATTLIST MENU
        COMPACT (COMPACT) #IMPLIED
        %SDAFORM; "List"
        %SDAPREF; "<LHead>Menu</LHead>"
        >
<!-- <DIR>              Directory list                  -->
<!-- <DIR COMPACT>      Compact list style              -->
<!-- <MENU>             Menu list                       -->
<!-- <MENU COMPACT>     Compact list style              -->
<!ELEMENT LI    - O %flow>
<!ATTLIST LI
        %SDAFORM; "LItem"
        >
<!-- <LI>               List item                       -->
<!--========== Document Body ===================-->
<![ %HTML.Recommended [        
<!ENTITY % body.content "(%heading|%block|HR|ADDRESS|IMG)*"        
-- <h1>Heading</h1>        
   <p>Text ...               
is preferred to        
   <h1>Heading</h1>        
   Text ...        
-->
]]>
<!ENTITY % body.content "(%heading | %text | %block |                          
 HR | ADDRESS)*">
<!ELEMENT BODY O O  %body.content>
<!-- <BODY>     Document body   -->
<!ELEMENT BLOCKQUOTE - - %body.content>
<!ATTLIST BLOCKQUOTE
        %SDAFORM; "BQ"
        >
<!-- <BLOCKQUOTE>       Quoted passage  -->
<!ELEMENT ADDRESS - - (%text|P)*>
<!ATTLIST  ADDRESS
        %SDAFORM; "Lit"
        %SDAPREF; "Address:&#RE;"
        >
<!-- <ADDRESS>  Address, signature, or byline    -->
<!--======= Forms ====================-->
<![ %HTML.Forms [
<!ELEMENT FORM - - %body.content -(FORM) +(INPUT|SELECT|TEXTAREA)>
<!ATTLIST FORM
        ACTION CDATA #IMPLIED
        METHOD (%HTTP-Method) GET
        ENCTYPE %Content-Type; "application/x-www-form-urlencoded"
        %SDAPREF; "<Para>Form:</Para>"
        %SDASUFF; "<Para>Form End.</Para>"
        >
<!-- <FORM>                     Fill-out or data-entry form     -->
<!-- <FORM ACTION="...">        Address for completed form      -->
<!-- <FORM METHOD=...>          Method of submitting form       -->
<!-- <FORM ENCTYPE="...">       Representation of form data     -->
<!ENTITY % InputType "(TEXT | PASSWORD | CHECKBOX |
                        RADIO | SUBMIT | RESET |
                        IMAGE | HIDDEN )">
<!ELEMENT INPUT - O EMPTY>
<!ATTLIST INPUT        
TYPE %InputType TEXT        
NAME CDATA #IMPLIED        
VALUE CDATA #IMPLIED        
SRC CDATA #IMPLIED        
CHECKED (CHECKED) #IMPLIED        
SIZE CDATA #IMPLIED        
MAXLENGTH NUMBER #IMPLIED        
ALIGN (top|middle|bottom) #IMPLIED
        %SDAPREF; "Input: "        
>
<!-- <INPUT>         Form input datum         -->
<!-- <INPUT TYPE=...>     Type of input interaction        -->
<!-- <INPUT NAME=...>     Name of form datum             -->
<!-- <INPUT VALUE="...">        Default/initial/selected value -->
<!-- <INPUT SRC="...">   Address of image               -->
<!-- <INPUT CHECKED>       Initial state is "on"         -->
<!-- <INPUT SIZE=...>     Field size hint           -->
<!-- <INPUT MAXLENGTH=...>      Data length maximum   -->
<!-- <INPUT ALIGN=...>   Image alignment                -->
<!ELEMENT SELECT - - (OPTION+) -(INPUT|SELECT|TEXTAREA)>
<!ATTLIST SELECT
        NAME CDATA #REQUIRED
        SIZE NUMBER #IMPLIED
        MULTIPLE (MULTIPLE) #IMPLIED
        %SDAFORM; "List"
        %SDAPREF;
        "<LHead>Select #AttVal(Multiple)</LHead>"        
>
<!-- <SELECT>      Selection of option(s)   -->
<!-- <SELECT NAME=...>   Name of form datum           -->
<!-- <SELECT SIZE=...>   Options displayed at a time     -->
<!-- <SELECT MULTIPLE>   Multiple selections allowed     -->
<!ELEMENT OPTION - O (#PCDATA)*>
<!ATTLIST OPTION
        SELECTED (SELECTED) #IMPLIED
        VALUE CDATA #IMPLIED
        %SDAFORM; "LItem"
        %SDAPREF;
        "Option: #AttVal(Value) #AttVal(Selected)"        
>
<!-- <OPTION>      A selection option           -->
<!-- <OPTION SELECTED>   Initial state      -->
<!-- <OPTION VALUE="...">       Form datum value for this option-->
<!ELEMENT TEXTAREA - - (#PCDATA)* -(INPUT|SELECT|TEXTAREA)>
<!ATTLIST TEXTAREA
        NAME CDATA #REQUIRED
        ROWS NUMBER #REQUIRED
        COLS NUMBER #REQUIRED
        %SDAFORM; "Para"
        %SDAPREF; "Input Text -- #AttVal(Name): "
        >
<!-- <TEXTAREA>                An area for text input               -->
<!-- <TEXTAREA NAME=...>        Name of form datum         -->
<!-- <TEXTAREA ROWS=...>        Height of area                -->
<!-- <TEXTAREA COLS=...>        Width of area           -->
]]>
<!--======= Document Head ======================-->
<![ %HTML.Recommended [        
<!ENTITY % head.extra "">
]]>
<!ENTITY % head.extra "& NEXTID?">
<!ENTITY % head.content "TITLE & ISINDEX? & BASE? %head.extra">
<!ELEMENT HEAD O O  (%head.content) +(META|LINK)>
<!-- <HEAD>     Document head   -->
<!ELEMENT TITLE - -  (#PCDATA)*  -(META|LINK)>
<!ATTLIST TITLE
        %SDAFORM; "Ti"    >
<!-- <TITLE>    Title of document -->
<!ELEMENT LINK - O EMPTY>
<!ATTLIST LINK
        HREF CDATA #REQUIRED
        %linkExtraAttributes;
        %SDAPREF; "Linked to : #AttVal (TITLE) (URN) (HREF)>"    >
<!-- <LINK>         Link from this document         -->
<!-- <LINK HREF="...">  Address of link destination           -->
<!-- <LINK URN="...">   Lasting name of destination             -->
<!-- <LINK REL=...>     Relationship to destination         -->
<!-- <LINK REV=...>     Relationship of destination to this         -->
<!-- <LINK TITLE="..."> Title of destination (advisory)         -->
<!-- <LINK METHODS="..."> Operations allowed (advisory)         -->
<!ELEMENT ISINDEX - O EMPTY>
<!ATTLIST ISINDEX
        %SDAPREF;
   "<Para>[Document is indexed/searchable.]</Para>">
<!-- <ISINDEX>          Document is a searchable index          -->
<!ELEMENT BASE - O EMPTY>
<!ATTLIST BASE
        HREF CDATA #REQUIRED     >
<!-- <BASE>             Base context document                   -->
<!-- <BASE HREF="...">  Address for this document               -->
<!ELEMENT NEXTID - O EMPTY>
<!ATTLIST NEXTID
        N CDATA #REQUIRED     >
<!-- <NEXTID>     Next ID to use for link name         -->
<!-- <NEXTID N=...>     Next ID to use for link name               -->
<!ELEMENT META - O EMPTY>
<!ATTLIST META
        HTTP-EQUIV  NAME    #IMPLIED
        NAME        NAME    #IMPLIED
        CONTENT     CDATA   #REQUIRED    >
<!-- <META>                     Generic Meta-information        -->
<!-- <META HTTP-EQUIV=...>      HTTP response header name       -->
<!-- <META NAME=...>            Meta-information name           -->
<!-- <META CONTENT="...">       Associated information          -->
<!--======= Document Structure =================-->
<![ %HTML.Deprecated [
        <!ENTITY % html.content "HEAD, BODY, PLAINTEXT?">
]]>
<!ENTITY % html.content "HEAD, BODY">
<!ELEMENT HTML O O  (%html.content)>
<!ENTITY % version.attr "VERSION CDATA #FIXED '%HTML.Version;'">
<!ATTLIST HTML
        %version.attr;
        %SDAFORM; "Book"
        >
<!-- <HTML>            HTML Document     -->
@end example


@node Strict HTML DTD,Level 1 HTML DTD,HTML DTD,HTML Public Text
@section Strict HTML DTD
This document type declaration refers to the HTML DTD with the
@samp{HTML.Recommended} entity defined as @samp{INCLUDE} rather than
IGNORE;  that is, it refers to the more structurally rigid definition
of HTML.

@example
<!--    html-s.dtd
        Document Type Definition for the HyperText Markup Language        
with strict validation (HTML Strict DTD).        
$Id: html-s.dtd,v 1.3 1995/06/02 18:55:46 connolly Exp $        
Author: Daniel W. Connolly <connolly@@w3.org>        
See Also: http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
-->
<!ENTITY % HTML.Version        
"-//IETF//DTD HTML 2.0 Strict//EN"
        -- Typical usage:
            <!DOCTYPE HTML PUBLIC               
"-//IETF//DTD HTML Strict//EN">        
    <html>        
    ...        
    </html>        
--        
>
<!-- Feature Test Entities -->
<!ENTITY % HTML.Recommended "INCLUDE">
<!ENTITY % html PUBLIC "-//IETF//DTD HTML 2.0//EN">
%html;
@end example


@node Level 1 HTML DTD,Strict Level 1 HTML DTD,Strict HTML DTD,HTML Public Text
@section Level 1 HTML DTD
This document type declaration refers to the HTML DTD with the
@samp{HTML.Forms} entity defined as @samp{IGNORE} rather than
@samp{INCLUDE}.  Documents which contain @emph{FORM} elements do not
conform to this DTD, and must use the level 2 DTD.

@example
<!--    html-1.dtd
        Document Type Definition for the HyperText Markup Language        
with Level 1 Extensions        (HTML Level 1 DTD).        
$Id: html-1.dtd,v 1.2 1995/03/29 18:53:10 connolly Exp $        
Author: Daniel W. Connolly <connolly@@w3.org>        
See Also: http://info.cern.ch/hypertext/WWW/MarkUp/MarkUp.html
-->
<!ENTITY % HTML.Version        
"-//IETF//DTD HTML 2.0 Level 1//EN"
        -- Typical usage:
            <!DOCTYPE HTML PUBLIC               
"-//IETF//DTD HTML Level 1//EN">        
    <html>        
    ...        
    </html>        
--        
>
<!-- Feature Test Entities -->
<!ENTITY % HTML.Forms "IGNORE">
<!ENTITY % html PUBLIC "-//IETF//DTD HTML 2.0//EN">
%html;
@end example


@node Strict Level 1 HTML DTD,SGML Declaration for HTML,Level 1 HTML DTD,HTML Public Text
@section Strict Level 1 HTML DTD
This document type declaration refers to the level 1 HTML DTD with the
@samp{HTML.Recommended} entity defined as @samp{INCLUDE} rather than
IGNORE;  that is, it refers to the more structurally rigid definition
of HTML.

@example
<!--    html-1s.dtd
        Document Type Definition for the HyperText Markup Language        
Struct Level 1        
$Id: html-1s.dtd,v 1.3 1995/06/02 18:55:43 connolly Exp $        
Author: Daniel W. Connolly <connolly@@w3.org>        
See Also: http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
-->
<!ENTITY % HTML.Version        
"-//IETF//DTD HTML 2.0 Strict Level 1//EN"
        -- Typical usage:
            <!DOCTYPE HTML PUBLIC               
"-//IETF//DTD HTML Strict Level 1//EN">        
    <html>        
    ...        
    </html>        
--        
>
<!-- Feature Test Entities -->
<!ENTITY % HTML.Recommended "INCLUDE">
<!ENTITY % html-1 PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN">
%html-1;
@end example


@node SGML Declaration for HTML,Sample SGML Open Entity Catalog for HTML,Strict Level 1 HTML DTD,HTML Public Text
@section SGML Declaration for HTML

This is the SGML Declaration for HyperText Markup Language.

@example
<!SGML  "ISO 8879:1986"
--        
SGML Declaration for HyperText Markup Language (HTML).
--
CHARSET
         BASESET  "ISO 646:1983//CHARSET
                   International Reference Version
                   (IRV)//ESC 2/5 4/0"
         DESCSET  0   9   UNUSED
                  9   2   9
                  11  2   UNUSED
                  13  1   13
                  14  18  UNUSED
                  32  95  32
                  127 1   UNUSED
     BASESET   "ISO Registration Number 100//CHARSET
                ECMA-94 Right Part of
                Latin Alphabet Nr. 1//ESC 2/13 4/1"
         DESCSET  128  32   UNUSED
                  160  96    32
CAPACITY        SGMLREF
                TOTALCAP        150000
                GRPCAP          150000               
ENTCAP               150000  
SCOPE    DOCUMENT
SYNTAX   
         SHUNCHAR CONTROLS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16               
 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 127
         BASESET  "ISO 646:1983//CHARSET
                   International Reference Version
                   (IRV)//ESC 2/5 4/0"
         DESCSET  0 128 0
         FUNCTION               
  RE          13
                  RS          10
                  SPACE       32
                  TAB SEPCHAR  9        
         NAMING   LCNMSTRT ""
                  UCNMSTRT ""
                  LCNMCHAR ".-"
                  UCNMCHAR ".-"
                  NAMECASE GENERAL YES
                           ENTITY  NO
         DELIM    GENERAL  SGMLREF
                  SHORTREF SGMLREF
         NAMES    SGMLREF
         QUANTITY SGMLREF
                  ATTSPLEN 2100
                  LITLEN   1024
                  NAMELEN  72    -- somewhat arbitrary; taken from
                                internet line length conventions --
                  PILEN    1024
                  TAGLVL   100
                  TAGLEN   2100
                  GRPGTCNT 150
                  GRPCNT   64                   
FEATURES
  MINIMIZE
    DATATAG  NO
    OMITTAG  YES
    RANK     NO
    SHORTTAG YES
  LINK
    SIMPLE   NO
    IMPLICIT NO
    EXPLICIT NO
  OTHER
    CONCUR   NO
    SUBDOC   NO
    FORMAL   YES
  APPINFO    "SDA"  -- conforming SGML Document Access application               
    --
>
<!--         
$Id: html.decl,v 1.17 1995/06/08 14:59:32 connolly Exp $        
Author: Daniel W. Connolly <connolly@@w3.org>        
See also: http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
 -->
@end example


@node Sample SGML Open Entity Catalog for HTML,Character Entity Sets,SGML Declaration for HTML,HTML Public Text
@section Sample SGML Open Entity Catalog for HTML

The SGML standard describes an ``entity manager'' as the portion or
component of an SGML system that maps SGML entities into the actual
storage model (e.g., the file system).  The standard itself does not
define a particular mapping methodology or notation.

To assist the interoperability among various SGML tools and
systems, the SGML Open consortium has passed a technical resolution
that defines a format for an application-independent entity catalog
that maps external identifiers and/or entity names to file names.

Each entry in the catalog associates a storage object identifier
(such as a file name) with information about the external entity that
appears in the SGML document.  In addition to entries that associate
public identifiers, a catalog entry can associate an entity name with
a storage object identifier.  For example, the following are possible
catalog entries:

@example        
-- catalog: SGML Open style entity catalog for HTML --        
-- $Id: catalog,v 1.3 1995/09/21 23:30:23 connolly Exp $ --        
-- Ways to refer to Level 2: most general to most specific --
PUBLIC  "-//IETF//DTD HTML//EN"                html.dtd
PUBLIC  "-//IETF//DTD HTML 2.0//EN"         html.dtd
PUBLIC  "-//IETF//DTD HTML Level 2//EN"         html.dtd
PUBLIC  "-//IETF//DTD HTML 2.0 Level 2//EN"     html.dtd        
-- Ways to refer to Level 1: most general to most specific --
PUBLIC  "-//IETF//DTD HTML Level 1//EN"         html-1.dtd
PUBLIC  "-//IETF//DTD HTML 2.0 Level 1//EN"     html-1.dtd        
-- Ways to refer to               
 Strict Level 2: most general to most specific --
PUBLIC  "-//IETF//DTD HTML Strict//EN"           html-s.dtd
PUBLIC  "-//IETF//DTD HTML 2.0 Strict//EN"           html-s.dtd
PUBLIC  "-//IETF//DTD HTML Strict Level 2//EN"   html-s.dtd
PUBLIC  "-//IETF//DTD HTML 2.0 Strict Level 2//EN"      html-s.dtd        
-- Ways to refer to               
 Strict Level 1: most general to most specific --
PUBLIC  "-//IETF//DTD HTML Strict Level 1//EN"   html-1s.dtd
PUBLIC  "-//IETF//DTD HTML 2.0 Strict Level 1//EN"      html-1s.dtd        
-- ISO latin 1 entity set for HTML -- 
PUBLIC  "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML"        ISOlat1.sgml
@end example


@node Character Entity Sets,,Sample SGML Open Entity Catalog for HTML,HTML Public Text
@section Character Entity Sets

The HTML DTD defines the following entities.  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.


@menu
* Numeric and Special Graphic Entity Set::
* ISO Latin 1 Character Entity Set::
@end menu
@node Numeric and Special Graphic Entity Set,ISO Latin 1 Character Entity Set,Character Entity Sets,Character Entity Sets
@subsection Numeric and Special Graphic Entity Set

The following table lists each of the characters included from the
Numeric and Special Graphic entity set, along with its name, syntax
for use, and description.  This list is derived from @samp{ISO Standard 8879:1986//ENTITIES Numeric and Special Graphic//EN}.  However,
HTML does not include for the entire entity set --- only the entities
listed below are included.

@example
GLYPH   NAME      SYNTAX       DESCRIPTION
<       lt      &lt;    Less than sign
>       gt      &gt;    Greater than sign
&       amp     &amp;   Ampersand
"       quot    &quot;  Double quote sign
@end example


@node ISO Latin 1 Character Entity Set,,Numeric and Special Graphic Entity Set,Character Entity Sets
@subsection ISO Latin 1 Character Entity Set

The following public text lists each of the characters specified in the
Added Latin 1 entity set, along with its name, syntax for use, and
description.  This list is derived from ISO Standard
8879:1986//ENTITIES Added Latin 1//EN@.  HTML includes the entire entity
set.

@example
<!-- (C) International Organization for Standardization 1986
     Permission to copy in any form is granted for use with
     conforming SGML systems and applications as defined in
     ISO 8879, provided this notice is included in all copies.
-->
<!-- Character entity set. Typical invocation:
     <!ENTITY % ISOlat1 PUBLIC
       "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
     %ISOlat1;
-->
<!--    Modified for use in HTML        
$Id: ISOlat1.sgml,v 1.2 1994/11/30 23:45:12 connolly Exp $ -->
<!ENTITY AElig  CDATA "&#198;" -- capital AE diphthong (ligature) -->
<!ENTITY Aacute CDATA "&#193;" -- capital A, acute accent -->
<!ENTITY Acirc  CDATA "&#194;" -- capital A, circumflex accent -->
<!ENTITY Agrave CDATA "&#192;" -- capital A, grave accent -->
<!ENTITY Aring  CDATA "&#197;" -- capital A, ring -->
<!ENTITY Atilde CDATA "&#195;" -- capital A, tilde -->
<!ENTITY Auml   CDATA "&#196;" -- capital A, dieresis or umlaut mark -->
<!ENTITY Ccedil CDATA "&#199;" -- capital C, cedilla -->
<!ENTITY ETH    CDATA "&#208;" -- capital Eth, Icelandic -->
<!ENTITY Eacute CDATA "&#201;" -- capital E, acute accent -->
<!ENTITY Ecirc  CDATA "&#202;" -- capital E, circumflex accent -->
<!ENTITY Egrave CDATA "&#200;" -- capital E, grave accent -->
<!ENTITY Euml   CDATA "&#203;" -- capital E, dieresis or umlaut mark -->
<!ENTITY Iacute CDATA "&#205;" -- capital I, acute accent -->
<!ENTITY Icirc  CDATA "&#206;" -- capital I, circumflex accent -->
<!ENTITY Igrave CDATA "&#204;" -- capital I, grave accent -->
<!ENTITY Iuml   CDATA "&#207;" -- capital I, dieresis or umlaut mark -->
<!ENTITY Ntilde CDATA "&#209;" -- capital N, tilde -->
<!ENTITY Oacute CDATA "&#211;" -- capital O, acute accent -->
<!ENTITY Ocirc  CDATA "&#212;" -- capital O, circumflex accent -->
<!ENTITY Ograve CDATA "&#210;" -- capital O, grave accent -->
<!ENTITY Oslash CDATA "&#216;" -- capital O, slash -->
<!ENTITY Otilde CDATA "&#213;" -- capital O, tilde -->
<!ENTITY Ouml   CDATA "&#214;" -- capital O, dieresis or umlaut mark -->
<!ENTITY THORN  CDATA "&#222;" -- capital THORN, Icelandic -->
<!ENTITY Uacute CDATA "&#218;" -- capital U, acute accent -->
<!ENTITY Ucirc  CDATA "&#219;" -- capital U, circumflex accent -->
<!ENTITY Ugrave CDATA "&#217;" -- capital U, grave accent -->
<!ENTITY Uuml   CDATA "&#220;" -- capital U, dieresis or umlaut mark -->
<!ENTITY Yacute CDATA "&#221;" -- capital Y, acute accent -->
<!ENTITY aacute CDATA "&#225;" -- small a, acute accent -->
<!ENTITY acirc  CDATA "&#226;" -- small a, circumflex accent -->
<!ENTITY aelig  CDATA "&#230;" -- small ae diphthong (ligature) -->
<!ENTITY agrave CDATA "&#224;" -- small a, grave accent -->
<!ENTITY aring  CDATA "&#229;" -- small a, ring -->
<!ENTITY atilde CDATA "&#227;" -- small a, tilde -->
<!ENTITY auml   CDATA "&#228;" -- small a, dieresis or umlaut mark -->
<!ENTITY ccedil CDATA "&#231;" -- small c, cedilla -->
<!ENTITY eacute CDATA "&#233;" -- small e, acute accent -->
<!ENTITY ecirc  CDATA "&#234;" -- small e, circumflex accent -->
<!ENTITY egrave CDATA "&#232;" -- small e, grave accent -->
<!ENTITY eth    CDATA "&#240;" -- small eth, Icelandic -->
<!ENTITY euml   CDATA "&#235;" -- small e, dieresis or umlaut mark -->
<!ENTITY iacute CDATA "&#237;" -- small i, acute accent -->
<!ENTITY icirc  CDATA "&#238;" -- small i, circumflex accent -->
<!ENTITY igrave CDATA "&#236;" -- small i, grave accent -->
<!ENTITY iuml   CDATA "&#239;" -- small i, dieresis or umlaut mark -->
<!ENTITY ntilde CDATA "&#241;" -- small n, tilde -->
<!ENTITY oacute CDATA "&#243;" -- small o, acute accent -->
<!ENTITY ocirc  CDATA "&#244;" -- small o, circumflex accent -->
<!ENTITY ograve CDATA "&#242;" -- small o, grave accent -->
<!ENTITY oslash CDATA "&#248;" -- small o, slash -->
<!ENTITY otilde CDATA "&#245;" -- small o, tilde -->
<!ENTITY ouml   CDATA "&#246;" -- small o, dieresis or umlaut mark -->
<!ENTITY szlig  CDATA "&#223;" -- small sharp s, German (sz ligature) -->
<!ENTITY thorn  CDATA "&#254;" -- small thorn, Icelandic -->
<!ENTITY uacute CDATA "&#250;" -- small u, acute accent -->
<!ENTITY ucirc  CDATA "&#251;" -- small u, circumflex accent -->
<!ENTITY ugrave CDATA "&#249;" -- small u, grave accent -->
<!ENTITY uuml   CDATA "&#252;" -- small u, dieresis or umlaut mark -->
<!ENTITY yacute CDATA "&#253;" -- small y, acute accent -->
<!ENTITY yuml   CDATA "&#255;" -- small y, dieresis or umlaut mark -->
@end example


@node Security Considerations,References,HTML Public Text,Top
@chapter Security Considerations
Anchors, embedded images, and all other elements which contain URIs as
parameters may cause the URI to be dereferenced in response to user
input.  In this case, the security considerations of [URL] apply.

The widely deployed methods for submitting forms requests --- HTTP and
SMTP --- provide little assurance of confidentiality.  Information
providers who request sensitive information via forms --- especially by
way of the @samp{PASSWORD} type input field (see @ref{Input Field;  INPUT})
--- should be aware and make their users aware of the lack of
confidentiality.


@node References,Acknowledgments,Security Considerations,Top
@chapter References

@table @emph
@item [URI]
T@.  Berners-Lee.  ``Universal Resource Identifiers in WWW:  A
Unifying Syntax for the Expression of Names and Addresses of Objects
on the Network as used in the World- Wide Web.'' RFC 1630, CERN, June 1994.
@emph{ftp://ds.internic.net/rfc/rfc1630.txt}

@item [URL]
T@.  Berners-Lee, L@.  Masinter, and M@.  McCahill.  ``Uniform
Resource Locators (URL).'' RFC 1738, CERN,
Xerox PARC, University of Minnesota, December 1994.
@emph{ftp://ds.internic.net/rfc/rfc1738.txt}

@item [HTTP]
T@.  Berners-Lee, R@.  T@.  Fielding, and H@.  Frystyk
Nielsen.  ``Hypertext Transfer Protocol - HTTP/1.0.'' Work in Progress, MIT,
UC Irvine, CERN, March 1995.
@emph{ftp://ds.internic.net/internet-drafts/draft-ietf-http-v10-spec-00.ps}

@item [MIME]
N@.  Borenstein and N@.  Freed.  ``MIME (Multipurpose Internet
Mail Extensions) Part One:  Mechanisms for Specifying and Describing
the Format of Internet Message Bodies.'' RFC 1521,
Bellcore, Innosoft, September 1993.
@emph{ftp://ds.internic.net/rfc/rfc1521.txt}

@item [RELURL]
R@.  Fielding.  ``Relative Uniform Resource Locators.''
RFC 1808, June 1995
@emph{ftp://ds.internic.net/rfc/rfc1808.txt}

@item [GOLD90]
C@.  F@.  Goldfarb.  ``The SGML Handbook.'' Y@.  Rubinsky, Ed.,
Oxford University Press, 1990.
@emph{}

@item [DEXTER]
Frank Halasz and Mayer Schwartz, ``The Dexter Hypertext
Reference Model'', ``Communications of the ACM'', pp.  30-39, vol.  37
no.  2, Feb 1994,
@emph{}

@item [IMEDIA]
J@.  Postel.  ``Media Type Registration Procedure.'',
USC/ISI, March 1994.  @emph{ftp://ds.internic.net/rfc/rfc1590.txt}

@item [IANA]
J@.  Reynolds and J@.  Postel.  ``Assigned Numbers.'' STD 2,
RFC 1700, USC/ISI, October 1994.
@emph{ftp://ds.internic.net/rfc/rfc1700.txt}

@item [SQ91]
SoftQuad.  ``The SGML Primer.'' 3rd ed., SoftQuad Inc.,
1991.  @emph{http://www.sq.com/}

@item [ISO-646]
ISO/IEC 646:1991
Information technology --- ISO 7-bit coded character set for
information interchange
@emph{http://www.iso.ch/cate/d4777.html}

@item [ISO-10646]
ISO/IEC 10646-1:1993
Information technology --- Universal Multiple-Octet Coded
Character Set (UCS) --- Part 1:  Architecture and Basic Multilingual
Plane 
@emph{http://www.iso.ch/cate/d18741.html}

@item [ISO-8859-1]
ISO 8859.  International Standard --- Information
Processing --- 8-bit Single-Byte Coded Graphic Character Sets --- Part
1:  Latin Alphabet No.  1, ISO 8859-1:1987.
@emph{http://www.iso.ch/cate/d16338.html}

@item [SGML]
ISO 8879.  Information Processing --- Text and Office
Systems - Standard Generalized Markup Language (SGML), 1986.
@emph{http://www.iso.ch/cate/d16387.html}

@end table


@node Acknowledgments,The HTML Coded Character Set,References,Top
@chapter Acknowledgments

The HTML document type was designed by Tim Berners-Lee at CERN as
part of the 1990 World Wide Web project.  In 1992, Dan Connolly wrote
the HTML Document Type Definition (DTD) and a brief HTML
specification.

Since 1993, a wide variety of Internet participants have
contributed to the evolution of HTML, which has included the addition
of in-line images introduced by the NCSA Mosaic software for WWW@.  Dave
Raggett played an important role in deriving the forms material from
the HTML+ specification.

Dan Connolly and Karen Olson Muldrow rewrote the HTML Specification
in 1994.  The document was then edited by the HTML working group as a
whole, with updates being made by Eric Schieler, Mike Knezovich, and
Eric W@.  Sink at Spyglass, Inc.  Finally, Roy Fielding restructured the
entire draft into its current form.

Special thanks to the many active participants in the HTML working
group, too numerous to list individually, without whom there would be
no standards process and no standard.  That this document approaches
its objective of carefully converging a description of current
practice and formalization of HTML's relationship to SGML is a tribute
to their effort.


@menu
* Authors^ Addresses::     Authors' Addresses
@end menu
@node Authors^ Addresses,,Acknowledgments,Acknowledgments
@section Authors' Addresses

@table @emph
@item Tim Berners-Lee

@example
Director, W3 Consortium
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139, U.S.A.
Tel: +1 (617) 253 9670
Fax: +1 (617) 258 8682
Email: timbl@@w3.org
@end example

@item Daniel W@.  Connolly

@example
Research Technical Staff, W3 Consortium
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139, U.S.A.
Fax: +1 (617) 258 8682
Email: connolly@@w3.org
URI: http://www.w3.org/hypertext/WWW/People/Connolly/
@end example

@end table


@node The HTML Coded Character Set,Proposed Entities,Acknowledgments,Top
@appendix The HTML Coded Character Set

This list details the code positions and characters of the HTML
document character set, specified in @ref{SGML Declaration for HTML}.  This coded
character set is based on [ISO-8859-1].

@example
REFERENCE       DESCRIPTION
--------------  -----------
&#00; - &#08;   Unused
&#09;     Horizontal tab
&#10;     Line feed
&#11; - &#12;   Unused
&#13;     Carriage Return
&#14; - &#31;   Unused
&#32;     Space
&#33;     Exclamation mark
&#34;     Quotation mark
&#35;     Number sign
&#36;     Dollar sign
&#37;     Percent sign
&#38;     Ampersand
&#39;     Apostrophe
&#40;     Left parenthesis
&#41;     Right parenthesis
&#42;     Asterisk
&#43;     Plus sign
&#44;     Comma
&#45;     Hyphen
&#46;     Period (fullstop)
&#47;     Solidus (slash)
&#48; - &#57;   Digits 0-9
&#58;     Colon
&#59;     Semi-colon
&#60;     Less than
&#61;     Equals sign
&#62;     Greater than
&#63;     Question mark
&#64;     Commercial at
&#65; - &#90;   Letters A-Z
&#91;     Left square bracket
&#92;     Reverse solidus (backslash)
&#93;     Right square bracket
&#94;     Caret
&#95;     Horizontal bar (underscore)
&#96;     Acute accent
&#97; - &#122;  Letters a-z
&#123;   Left curly brace
&#124;   Vertical bar
&#125;   Right curly brace
&#126;   Tilde
&#127; - &#159; Unused
&#160;          Non-breaking Space
&#161;   Inverted exclamation
&#162;   Cent sign
&#163;   Pound sterling
&#164;   General currency sign
&#165;   Yen sign
&#166;   Broken vertical bar
&#167;   Section sign
&#168;   Umlaut (dieresis)
&#169;   Copyright
&#170;   Feminine ordinal
&#171;   Left angle quote, guillemotleft
&#172;   Not sign
&#173;   Soft hyphen
&#174;   Registered trademark
&#175;   Macron accent
&#176;   Degree sign
&#177;   Plus or minus
&#178;   Superscript two
&#179;   Superscript three
&#180;   Acute accent
&#181;   Micro sign
&#182;   Paragraph sign
&#183;   Middle dot
&#184;   Cedilla
&#185;   Superscript one
&#186;   Masculine ordinal
&#187;   Right angle quote, guillemotright
&#188;   Fraction one-fourth
&#189;   Fraction one-half
&#190;   Fraction three-fourths
&#191;   Inverted question mark
&#192;   Capital A, grave accent
&#193;   Capital A, acute accent
&#194;   Capital A, circumflex accent
&#195;   Capital A, tilde
&#196;   Capital A, dieresis or umlaut mark
&#197;   Capital A, ring
&#198;   Capital AE dipthong (ligature)
&#199;   Capital C, cedilla
&#200;   Capital E, grave accent
&#201;   Capital E, acute accent
&#202;   Capital E, circumflex accent
&#203;   Capital E, dieresis or umlaut mark
&#204;   Capital I, grave accent
&#205;   Capital I, acute accent
&#206;   Capital I, circumflex accent
&#207;   Capital I, dieresis or umlaut mark
&#208;   Capital Eth, Icelandic
&#209;   Capital N, tilde
&#210;   Capital O, grave accent
&#211;   Capital O, acute accent
&#212;   Capital O, circumflex accent
&#213;   Capital O, tilde
&#214;   Capital O, dieresis or umlaut mark
&#215;   Multiply sign
&#216;   Capital O, slash
&#217;   Capital U, grave accent
&#218;   Capital U, acute accent
&#219;   Capital U, circumflex accent
&#220;   Capital U, dieresis or umlaut mark
&#221;   Capital Y, acute accent
&#222;   Capital THORN, Icelandic
&#223;   Small sharp s, German (sz ligature)
&#224;   Small a, grave accent
&#225;   Small a, acute accent
&#226;   Small a, circumflex accent
&#227;   Small a, tilde
&#228;   Small a, dieresis or umlaut mark
&#229;   Small a, ring
&#230;   Small ae dipthong (ligature)
&#231;   Small c, cedilla
&#232;   Small e, grave accent
&#233;   Small e, acute accent
&#234;   Small e, circumflex accent
&#235;   Small e, dieresis or umlaut mark
&#236;   Small i, grave accent
&#237;   Small i, acute accent
&#238;   Small i, circumflex accent
&#239;   Small i, dieresis or umlaut mark
&#240;   Small eth, Icelandic
&#241;   Small n, tilde
&#242;   Small o, grave accent
&#243;   Small o, acute accent
&#244;   Small o, circumflex accent
&#245;   Small o, tilde
&#246;   Small o, dieresis or umlaut mark
&#247;   Division sign
&#248;   Small o, slash
&#249;   Small u, grave accent
&#250;   Small u, acute accent
&#251;   Small u, circumflex accent
&#252;   Small u, dieresis or umlaut mark
&#253;   Small y, acute accent
&#254;   Small thorn, Icelandic
&#255;   Small y, dieresis or umlaut mark
@end example


@node Proposed Entities,,The HTML Coded Character Set,Top
@appendix Proposed Entities

The HTML DTD references the ``Added Latin 1'' entity set, which only
supplies named entities for a subset of the non-ASCII characters in
[ISO-8859-1], namely the accented characters.  The following entities
should be supported so that all ISO 8859-1 characters may only be
referenced symbolically.  The names for these entities are taken
from the appendixes of [SGML].

@example
<!ENTITY nbsp   CDATA "&#160;" -- no-break space -->
<!ENTITY iexcl  CDATA "&#161;" -- inverted exclamation mark -->
<!ENTITY cent   CDATA "&#162;" -- cent sign -->
<!ENTITY pound  CDATA "&#163;" -- pound sterling sign -->
<!ENTITY curren CDATA "&#164;" -- general currency sign -->
<!ENTITY yen    CDATA "&#165;" -- yen sign -->
<!ENTITY brvbar CDATA "&#166;" -- broken (vertical) bar -->
<!ENTITY sect   CDATA "&#167;" -- section sign -->
<!ENTITY uml    CDATA "&#168;" -- umlaut (dieresis) -->
<!ENTITY copy   CDATA "&#169;" -- copyright sign -->
<!ENTITY ordf   CDATA "&#170;" -- ordinal indicator, feminine -->
<!ENTITY laquo  CDATA "&#171;" -- angle quotation mark, left -->
<!ENTITY not    CDATA "&#172;" -- not sign -->
<!ENTITY shy    CDATA "&#173;" -- soft hyphen -->
<!ENTITY reg    CDATA "&#174;" -- registered sign -->
<!ENTITY macr   CDATA "&#175;" -- macron -->
<!ENTITY deg    CDATA "&#176;" -- degree sign -->
<!ENTITY plusmn CDATA "&#177;" -- plus-or-minus sign -->
<!ENTITY sup2   CDATA "&#178;" -- superscript two -->
<!ENTITY sup3   CDATA "&#179;" -- superscript three -->
<!ENTITY acute  CDATA "&#180;" -- acute accent -->
<!ENTITY micro  CDATA "&#181;" -- micro sign -->
<!ENTITY para   CDATA "&#182;" -- pilcrow (paragraph sign) -->
<!ENTITY middot CDATA "&#183;" -- middle dot -->
<!ENTITY cedil  CDATA "&#184;" -- cedilla -->
<!ENTITY sup1   CDATA "&#185;" -- superscript one -->
<!ENTITY ordm   CDATA "&#186;" -- ordinal indicator, masculine -->
<!ENTITY raquo  CDATA "&#187;" -- angle quotation mark, right -->
<!ENTITY frac14 CDATA "&#188;" -- fraction one-quarter -->
<!ENTITY frac12 CDATA "&#189;" -- fraction one-half -->
<!ENTITY frac34 CDATA "&#190;" -- fraction three-quarters -->
<!ENTITY iquest CDATA "&#191;" -- inverted question mark -->
<!ENTITY Agrave CDATA "&#192;" -- capital A, grave accent -->
<!ENTITY Aacute CDATA "&#193;" -- capital A, acute accent -->
<!ENTITY Acirc  CDATA "&#194;" -- capital A, circumflex accent -->
<!ENTITY Atilde CDATA "&#195;" -- capital A, tilde -->
<!ENTITY Auml   CDATA "&#196;" -- capital A, dieresis or umlaut mark -->
<!ENTITY Aring  CDATA "&#197;" -- capital A, ring -->
<!ENTITY AElig  CDATA "&#198;" -- capital AE diphthong (ligature) -->
<!ENTITY Ccedil CDATA "&#199;" -- capital C, cedilla -->
<!ENTITY Egrave CDATA "&#200;" -- capital E, grave accent -->
<!ENTITY Eacute CDATA "&#201;" -- capital E, acute accent -->
<!ENTITY Ecirc  CDATA "&#202;" -- capital E, circumflex accent -->
<!ENTITY Euml   CDATA "&#203;" -- capital E, dieresis or umlaut mark -->
<!ENTITY Igrave CDATA "&#204;" -- capital I, grave accent -->
<!ENTITY Iacute CDATA "&#205;" -- capital I, acute accent -->
<!ENTITY Icirc  CDATA "&#206;" -- capital I, circumflex accent -->
<!ENTITY Iuml   CDATA "&#207;" -- capital I, dieresis or umlaut mark -->
<!ENTITY ETH    CDATA "&#208;" -- capital Eth, Icelandic -->
<!ENTITY Ntilde CDATA "&#209;" -- capital N, tilde -->
<!ENTITY Ograve CDATA "&#210;" -- capital O, grave accent -->
<!ENTITY Oacute CDATA "&#211;" -- capital O, acute accent -->
<!ENTITY Ocirc  CDATA "&#212;" -- capital O, circumflex accent -->
<!ENTITY Otilde CDATA "&#213;" -- capital O, tilde -->
<!ENTITY Ouml   CDATA "&#214;" -- capital O, dieresis or umlaut mark -->
<!ENTITY times  CDATA "&#215;" -- multiply sign -->
<!ENTITY Oslash CDATA "&#216;" -- capital O, slash -->
<!ENTITY Ugrave CDATA "&#217;" -- capital U, grave accent -->
<!ENTITY Uacute CDATA "&#218;" -- capital U, acute accent -->
<!ENTITY Ucirc  CDATA "&#219;" -- capital U, circumflex accent -->
<!ENTITY Uuml   CDATA "&#220;" -- capital U, dieresis or umlaut mark -->
<!ENTITY Yacute CDATA "&#221;" -- capital Y, acute accent -->
<!ENTITY THORN  CDATA "&#222;" -- capital THORN, Icelandic -->
<!ENTITY szlig  CDATA "&#223;" -- small sharp s, German (sz ligature) -->
<!ENTITY agrave CDATA "&#224;" -- small a, grave accent -->
<!ENTITY aacute CDATA "&#225;" -- small a, acute accent -->
<!ENTITY acirc  CDATA "&#226;" -- small a, circumflex accent -->
<!ENTITY atilde CDATA "&#227;" -- small a, tilde -->
<!ENTITY auml   CDATA "&#228;" -- small a, dieresis or umlaut mark -->
<!ENTITY aring  CDATA "&#229;" -- small a, ring -->
<!ENTITY aelig  CDATA "&#230;" -- small ae diphthong (ligature) -->
<!ENTITY ccedil CDATA "&#231;" -- small c, cedilla -->
<!ENTITY egrave CDATA "&#232;" -- small e, grave accent -->
<!ENTITY eacute CDATA "&#233;" -- small e, acute accent -->
<!ENTITY ecirc  CDATA "&#234;" -- small e, circumflex accent -->
<!ENTITY euml   CDATA "&#235;" -- small e, dieresis or umlaut mark -->
<!ENTITY igrave CDATA "&#236;" -- small i, grave accent -->
<!ENTITY iacute CDATA "&#237;" -- small i, acute accent -->
<!ENTITY icirc  CDATA "&#238;" -- small i, circumflex accent -->
<!ENTITY iuml   CDATA "&#239;" -- small i, dieresis or umlaut mark -->
<!ENTITY eth    CDATA "&#240;" -- small eth, Icelandic -->
<!ENTITY ntilde CDATA "&#241;" -- small n, tilde -->
<!ENTITY ograve CDATA "&#242;" -- small o, grave accent -->
<!ENTITY oacute CDATA "&#243;" -- small o, acute accent -->
<!ENTITY ocirc  CDATA "&#244;" -- small o, circumflex accent -->
<!ENTITY otilde CDATA "&#245;" -- small o, tilde -->
<!ENTITY ouml   CDATA "&#246;" -- small o, dieresis or umlaut mark -->
<!ENTITY divide CDATA "&#247;" -- divide sign -->
<!ENTITY oslash CDATA "&#248;" -- small o, slash -->
<!ENTITY ugrave CDATA "&#249;" -- small u, grave accent -->
<!ENTITY uacute CDATA "&#250;" -- small u, acute accent -->
<!ENTITY ucirc  CDATA "&#251;" -- small u, circumflex accent -->
<!ENTITY uuml   CDATA "&#252;" -- small u, dieresis or umlaut mark -->
<!ENTITY yacute CDATA "&#253;" -- small y, acute accent -->
<!ENTITY thorn  CDATA "&#254;" -- small thorn, Icelandic -->
<!ENTITY yuml   CDATA "&#255;" -- small y, dieresis or umlaut mark -->
@end example

@contents
@bye
