RISC DISC 2/RISC_DISC_2.iso/the_web/documents/spec/html_spec/intro_sgm

Text File | 1995-06-15 | 5.1 KB | 141 lines

<!-- $Id: intro.sgm,v 1.12 1995/06/15 20:17:08 connolly Exp $ -->
<h1>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].

<h2>Scope

HTML has been in use by the World-Wide Web (WWW) global information
initiative since 1990. This specification corresponds to the
capabilities of HTML in common use prior to June 1994 and referred to
as "HTML 2.0".

HTML is an application of ISO Standard 8879:1986 <emph>Information
Processing Text and Office Systems; Standard Generalized Markup
Language</emph> (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 <code>text/html</>. As such, it
defines the semantics of the HTML syntax and how that syntax should be
interpreted by user agents.

<h2>Conformance

This specification governs the syntax of HTML documents and aspects of
the behavior of HTML user agents.

<h3>Documents

A document is a conforming HTML document if:

<ul>
<li>It is a conforming SGML document, and it conforms to the HTML DTD
(see <hdref refid=dtd>).
<note>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.
</note>

<li>It conforms to the application conventions in this
specification. For example, the value of the <attr/HREF/ attribute of
the <tag/A/ element must conform to the URI syntax.

<li>Its document character set includes [ISO-8859-1] and agrees with
[ISO-10646]; that is, each code position listed in <hdref
refid=iso-latin-1> 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.
<note>The document character set is somewhat independent of the
character encoding scheme used to represent a document. For example,
the <code/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.
</note>

</ul>


<h3 id=feature-test>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.

<tl>
<tli>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 <code/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.

<tli>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 <code/INCLUDE/ by default.

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

</tl>

<h3>User Agents

An HTML user agent conforms to this specification if:

<ul>
<li>It parses the characters of an HTML document into data characters
and markup according to [SGML].
<note>
In the interest of robustness and extensibility, there are a number
of widely deployed conventions for handling non-conforming documents.
See <hdref refid=conv1> for details.
</note>

<li>It supports the <code/ISO-8859-1/ character encoding scheme and
processes each character in the ISO Latin Alphabet No. 1 as specified
in <hdref refid=charlist>.
<note>To support non-western writing systems, HTML user agents are
encouraged to support <code/ISO-10646-UCS-2/ or similar character
encoding schemes and as much of the character repertoire of
[ISO-10646] as is practical.
</note>

<li>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.

<li>It allows the user to traverse (or at least attempt to traverse,
resources permitting) all hyperlinks from <tag/A/ elements in an HTML
document.

</ul>

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

<ul>
<li>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.
</ul>