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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- Copyright (c) 1998, 1999 Nik Clayton, All rights reserved.
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(SGML HTML, PDF, PostScript, RTF and so forth) with or without
modification, are permitted provided that the following conditions
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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POSSIBILITY OF SUCH DAMAGE.
$FreeBSD$
-->
<chapter id="xhtml-markup">
<title><acronym>XHTML</acronym> Markup</title>
<sect1 id="xhtml-markup-introduction">
<title>Introduction</title>
<para>This chapter describes usage of the <acronym>XHTML</acronym>
markup language used for the &os; web site.</para>
<para><acronym>XHTML</acronym> is the <acronym>XML</acronym>
version of the HyperText Markup Language, the markup language of
choice on the World Wide Web. More information can be found at
<ulink url="http://www.w3.org/"></ulink>.</para>
<para><acronym>XHTML</acronym> is used to mark up pages on the
&os; web site. It is usually not used to mark up other
documentation, since DocBook offers a far richer set of elements
from which to choose. Consequently, <acronym>XHTML</acronym>
pages will normally only be encountered when writing for the web
site.</para>
<para><acronym>HTML</acronym> has gone through a number of
versions. The <acronym>XML</acronym>-compliant version
described here is called <acronym>XHTML</acronym>. The latest
widespread version is <acronym>XHTML</acronym> 1.0, available in
both <emphasis>strict</emphasis> and
<emphasis>transitional</emphasis> variants.</para>
<para>The <acronym>XHTML</acronym> <acronym>DTDs</acronym> are
available from the Ports Collection in
<filename role="package">textproc/xhtml</filename>. They are
automatically installed as part of the <filename
role="package">textproc/docproj</filename> port.</para>
<note>
<para>This is <emphasis>not</emphasis> an exhaustive list of
elements, since that would just repeat the documentation for
<acronym>XHTML</acronym>. The aim is to list those elements
most commonly used. Please post questions about elements or
uses not covered here to the &a.doc;.</para>
</note>
<note>
<title>Inline Versus Block</title>
<para>In the remainder of this document, when describing
elements, <emphasis>inline</emphasis> means that the element
can occur within a block element, and does not cause a line
break. A <emphasis>block</emphasis> element, by comparison,
will cause a line break (and other processing) when it is
encountered.</para>
</note>
</sect1>
<sect1 id="xhtml-markup-fpi">
<title>Formal Public Identifier (<acronym>FPI</acronym>)</title>
<para>There are a number of <acronym>XHTML</acronym>
<acronym>FPI</acronym>s, depending upon the version, or
<emphasis>level</emphasis> of <acronym>XHTML</acronym> to which
a document conforms. Most XHTML documents on the FreeBSD web
site comply with the transitional version of
<acronym>XHTML</acronym> 1.0.</para>
<programlisting>PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"</programlisting>
</sect1>
<sect1 id="xhtml-markup-sectional-elements">
<title>Sectional Elements</title>
<para>An <acronym>XHTML</acronym> document is normally split into
two sections. The first section, called the
<emphasis>head</emphasis>, contains meta-information about the
document, such as its title, the name of the author, the parent
document, and so on. The second section, the
<emphasis>body</emphasis>, contains the content that will be
displayed to the user.</para>
<para>These sections are indicated with <sgmltag>head</sgmltag>
and <sgmltag>body</sgmltag> elements respectively. These
elements are contained within the top-level
<sgmltag>html</sgmltag> element.</para>
<example>
<title>Normal <acronym>XHTML</acronym> Document
Structure</title>
<programlisting><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title><replaceable>The Document's Title</replaceable></title>
</head>
<body>
…
</body>
</html></programlisting>
</example>
</sect1>
<sect1 id="xhtml-markup-block-elements">
<title>Block Elements</title>
<sect2 id="xhtml-markup-block-elements-headings">
<title>Headings</title>
<para><acronym>XHTML</acronym> has tags to denote headings in
the document at up to six different levels.</para>
<para>The largest and most prominent heading is
<sgmltag>h1</sgmltag>, then <sgmltag>h2</sgmltag>,
continuing down to <sgmltag>h6</sgmltag>.</para>
<para>The element's content is the text of the heading.</para>
<example>
<title><sgmltag>h1</sgmltag>, <sgmltag>h2</sgmltag>,
and Other Header Tags</title>
<para>Usage:</para>
<programlisting><![CDATA[<h1>First section</h1>
<!-- Document introduction goes here -->
<h2>This is the heading for the first section</h2>
<!-- Content for the first section goes here -->
<h3>This is the heading for the first sub-section</h3>
<!-- Content for the first sub-section goes here -->
<h2>This is the heading for the second section</h2>
<!-- Content for the second section goes here -->]]></programlisting>
</example>
<para>Generally, an <acronym>XHTML</acronym> page should have
one first level heading (<sgmltag>h1</sgmltag>). This can
contain many second level headings (<sgmltag>h2</sgmltag>),
which can in turn contain many third level headings. Each
<sgmltag>h<replaceable>n</replaceable></sgmltag> element
should have the same element, but one further up the
hierarchy, preceding it. Leaving gaps in the numbering is to
be avoided.</para>
<example>
<title>Bad Ordering of
<sgmltag>h<replaceable>n</replaceable></sgmltag>
Elements</title>
<para>Usage:</para>
<programlisting><![CDATA[<h1>First section</h1>
<!-- Document introduction -->
<h3>Sub-section</h3>
<!-- This is bad, <h2> has been left out -->]]></programlisting>
</example>
</sect2>
<sect2 id="xhtml-markup-block-elements-paragraphs">
<title>Paragraphs</title>
<para><acronym>XHTML</acronym> supports a single paragraph
element, <sgmltag>p</sgmltag>.</para>
<example>
<title><sgmltag>p</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>This is a paragraph. It can contain just about any
other element.</p>]]></programlisting>
</example>
</sect2>
<sect2 id="xhtml-markup-block-elements-block-quotations">
<title>Block Quotations</title>
<para>A block quotation is an extended quotation from another
document that should not appear within the current
paragraph.</para>
<example>
<title><sgmltag>blockquote</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>A small excerpt from the US Constitution:</p>
<blockquote>We the People of the United States, in Order to form
a more perfect Union, establish Justice, insure domestic
Tranquility, provide for the common defence, promote the general
Welfare, and secure the Blessings of Liberty to ourselves and our
Posterity, do ordain and establish this Constitution for the
United States of America.</blockquote>]]></programlisting>
</example>
</sect2>
<sect2 id="xhtml-markup-block-elements-lists">
<title>Lists</title>
<para><acronym>XHTML</acronym> can present the user with three
types of lists: ordered, unordered, and definition.</para>
<para>Typically, each entry in an ordered list will be
numbered, while each entry in an unordered list will be
preceded by a bullet point. Definition lists are composed of
two sections for each entry. The first section is the term
being defined, and the second section is the definition of the
term.</para>
<para>Ordered lists are indicated by the <sgmltag>ol</sgmltag>
element, unordered lists by the <sgmltag>ul</sgmltag>
element, and definition lists by the <sgmltag>dl</sgmltag>
element.</para>
<para>Ordered and unordered lists contain listitems, indicated
by the <sgmltag>li</sgmltag> element. A listitem can
contain textual content, or it may be further wrapped in one
or more <sgmltag>p</sgmltag> elements.</para>
<para>Definition lists contain definition terms
(<sgmltag>dt</sgmltag>) and definition descriptions
(<sgmltag>dd</sgmltag>). A definition term can only contain
inline elements. A definition description can contain other
block elements.</para>
<example>
<title><sgmltag>ul</sgmltag> and
<sgmltag>ol</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>An unordered list. Listitems will probably be
preceded by bullets.</p>
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
</ul>
<p>An ordered list, with list items consisting of multiple
paragraphs. Each item (note: not each paragraph) will be
numbered.</p>
<ol>
<li><p>This is the first item. It only has one paragraph.</p></li>
<li><p>This is the first paragraph of the second item.</p>
<p>This is the second paragraph of the second item.</p></li>
<li><p>This is the first and only paragraph of the third
item.</p></li>
</ol>]]></programlisting>
</example>
<example>
<title>Definition Lists with <sgmltag>dl</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<dl>
<dt>Term 1</dt>
<dd><p>Paragraph 1 of definition 1.</p>
<p>Paragraph 2 of definition 1.</p></dd>
<dt>Term 2</dt>
<dd><p>Paragraph 1 of definition 2.</p></dd>
<dt>Term 3</dt>
<dd><p>Paragraph 1 of definition 3.</p></dd>
</dl>]]></programlisting>
</example>
</sect2>
<sect2 id="xhtml-markup-block-elements-preformatted-text">
<title>Pre-formatted Text</title>
<para>Pre-formatted text can be shown to the user exactly as it
is in the file. Typically, this means that the text is shown
in a fixed font, multiple spaces are not merged into one, and
line breaks in the text are significant.</para>
<para>In order to do this, wrap the content in the
<sgmltag>pre</sgmltag> element.</para>
<example>
<title><sgmltag>pre</sgmltag></title>
<para>For example, the <sgmltag>pre</sgmltag> tags could be
used to mark up an email message:</para>
<programlisting><![CDATA[<pre> From: nik@FreeBSD.org
To: freebsd-doc@FreeBSD.org
Subject: New documentation available
There is a new copy of my primer for contributors to the FreeBSD
Documentation Project available at
<URL:http://people.FreeBSD.org/~nik/primer/index.html>
Comments appreciated.
N</pre>]]></programlisting>
<para>Keep in mind that <literal><</literal> and
<literal>&</literal> still are recognized as special
characters in pre-formatted text. This is why the example
shown had to use <literal>&lt;</literal> instead of
<literal><</literal>. For consistency,
<literal>&gt;</literal> was used in place of
<literal>></literal>, too. Watch out for the special
characters that may appear in text copied from a plain-text
source, like an email message or program code.</para>
</example>
</sect2>
<sect2 id="xhtml-markup-block-elements-tables">
<title>Tables</title>
<para>Mark up tabular information using the
<sgmltag>table</sgmltag> element. A table consists of one or
more table rows (<sgmltag>tr</sgmltag>), each containing one
or more cells of table data (<sgmltag>td</sgmltag>). Each
cell can contain other block elements, such as paragraphs or
lists. It can also contain another table (this nesting can
repeat indefinitely). If the cell only contains one paragraph
then the <sgmltag>p</sgmltag>element is not needed.</para>
<example>
<title>Simple Use of <sgmltag>table</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>This is a simple 2x2 table.</p>
<table>
<tr>
<td>Top left cell</td>
<td>Top right cell</td>
</tr>
<tr>
<td>Bottom left cell</td>
<td>Bottom right cell</td>
</tr>
</table>]]></programlisting>
</example>
<para>A cell can span multiple rows and columns. To indicate
this, add the <literal>rowspan</literal> and/or
<literal>colspan</literal> attributes, with values indicating
the number of rows or columns that should be spanned.</para>
<example>
<title>Using <literal>rowspan</literal></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>One tall thin cell on the left, two short cells next to
it on the right.</p>
<table>
<tr>
<td rowspan="2">Long and thin</td>
</tr>
<tr>
<td>Top cell</td>
<td>Bottom cell</td>
</tr>
</table>]]></programlisting>
</example>
<example>
<title>Using <literal>colspan</literal></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>One long cell on top, two short cells below it.</p>
<table>
<tr>
<td colspan="2">Top cell</td>
</tr>
<tr>
<td>Bottom left cell</td>
<td>Bottom right cell</td>
</tr>
</table>]]></programlisting>
</example>
<example>
<title>Using <literal>rowspan</literal> and
<literal>colspan</literal> Together</title>
<para>Usage:</para>
<programlisting><![CDATA[<p>On a 3x3 grid, the top left block is a 2x2 set of
cells merged into one. The other cells are normal.</p>
<table>
<tr>
<td colspan="2" rowspan="2">Top left large cell</td>
<td>Top right cell</td>
</tr>
<tr>
<!-- Because the large cell on the left merges into
this row, the first <td> will occur on its
right -->
<td>Middle right cell</td>
</tr>
<tr>
<td>Bottom left cell</td>
<td>Bottom middle cell</td>
<td>Bottom right cell</td>
</tr>
</table>]]></programlisting>
</example>
</sect2>
</sect1>
<sect1 id="xhtml-markup-inline-elements">
<title>In-line Elements</title>
<sect2 id="xhtml-markup-inline-elements-emphasizing-information">
<title>Emphasizing Information</title>
<para>Two levels of emphasis are available in
<acronym>XHTML</acronym>, <sgmltag>em</sgmltag> and
<sgmltag>strong</sgmltag>. <sgmltag>em</sgmltag> is for a
normal level of emphasis and <sgmltag>strong</sgmltag>
indicates stronger emphasis.</para>
<para>Typically, <sgmltag>em</sgmltag> is rendered in italic
and <sgmltag>strong</sgmltag> is rendered in bold. This is
not always the case, however, and should not be relied upon.
According to best practices, webpages only hold structural and
semantical information and stylesheets are later applied to
them. Think of semantics, not formatting, when using these
tags.</para>
<example>
<title><sgmltag>em</sgmltag> and
<sgmltag>strong</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<p><em>This</em> has been emphasized, while
<strong>this</strong> has been strongly emphasized.</p>]]></programlisting>
</example>
</sect2>
<sect2 id="xhtml-markup-inline-elements-fixed-pitch-text">
<title>Indicating Fixed-Pitch Text</title>
<para>Content that should be rendered in a fixed pitch
(typewriter) typeface is tagged with <sgmltag>tt</sgmltag>
(for <quote>teletype</quote>).</para>
<example>
<title><sgmltag>tt</sgmltag></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>This document was originally written by
Nik Clayton, who can be reached by email as
<tt>nik@FreeBSD.org</tt>.</p>]]></programlisting>
</example>
</sect2>
<sect2 id="xhtml-markup-inline-elements-links">
<title>Links</title>
<note>
<para>Links are also inline elements.</para>
</note>
<sect3 id="xhtml-markup-inline-elements-linking">
<title>Linking to Other Documents on the Web</title>
<para>A link points to the <acronym>URL</acronym> of another
document on the web. The link is indicated with
<sgmltag>a</sgmltag>, and the <literal>href</literal>
attribute contains the <acronym>URL</acronym> of the target
document. The content of the element becomes the link, and
is normally indicated to the user in some way,
typically by a different color or underlining.</para>
<example>
<title>Using <literal><a href="..."></literal></title>
<para>Usage:</para>
<programlisting><![CDATA[<p>More information is available at the
<a href="http://www.FreeBSD.org/">FreeBSD web site</a>.</p>]]></programlisting>
</example>
<para>These links will take the user to the top of the chosen
document.</para>
</sect3>
<sect3 id="xhtml-markup-inline-elements-other-parts">
<title>Linking to Other Parts of Documents</title>
<para>Linking to a point within another document, or within
the same document, requires that the document author include
<emphasis>anchors</emphasis>. Anchors are indicated with
<sgmltag>a</sgmltag> and the <literal>id</literal> attribute
instead of <literal>href</literal>.</para>
<example>
<title>Using <literal><a id="..."></literal></title>
<para>Usage:</para>
<programlisting><![CDATA[<p><a id="para1">This</a> paragraph can be referenced
in other links with the name <tt>para1</tt>.</p>]]></programlisting>
</example>
<para>To link to a named part of a document, write a normal
link to that document, but include the <acronym>ID</acronym>
of the anchor after a <literal>#</literal> symbol.</para>
<example>
<title>Linking to a Named Part of Another Document</title>
<para>Assume that the <literal>para1</literal> example
resides in a document called
<filename>foo.html</filename>.</para>
<programlisting><![CDATA[<p>More information can be found in the
<a href="foo.html#para1">first paragraph</a> of
<tt>foo.html</tt>.</p>]]></programlisting>
</example>
<para>If you are linking to a named anchor within the same
document then you can omit the document's URL, and just
include the name of the anchor (with the preceding
<literal>#</literal>).</para>
<example>
<title>Linking to a Named Part of the Same Document</title>
<para>Assume that the <literal>para1</literal> example
resides in this document:</para>
<programlisting><![CDATA[<p>More information can be found in the
<a href="#para1">first paragraph</a> of this
document.</p>]]></programlisting>
</example>
</sect3>
</sect2>
</sect1>
</chapter>
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