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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- Copyright (c) 1998, 1999 Nik Clayton, All rights reserved.

     Redistribution and use in source (SGML DocBook) and 'compiled' forms
     (SGML HTML, PDF, PostScript, RTF and so forth) with or without
     modification, are permitted provided that the following conditions
     are met:

      1. Redistributions of source code (SGML DocBook) must retain the above
         copyright notice, this list of conditions and the following
         disclaimer as the first lines of this file unmodified.

      2. Redistributions in compiled form (transformed to other DTDs,
         converted to PDF, PostScript, RTF and other formats) must reproduce
         the above copyright notice, this list of conditions and the
         following disclaimer in the documentation and/or other materials
         provided with the distribution.

     THIS DOCUMENTATION IS PROVIDED BY NIK CLAYTON "AS IS" AND ANY EXPRESS OR
     IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     DISCLAIMED. IN NO EVENT SHALL NIK CLAYTON BE LIABLE FOR ANY DIRECT,
     INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
     ANY WAY OUT OF THE USE OF THIS DOCUMENTATION, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.

     $FreeBSD$
-->

<chapter id="xml-markup">
  <title>XML Markup</title>

  <para>This chapter describes the two markup languages you will
    encounter when you contribute to the FreeBSD documentation
    project.  Each section describes the markup language, and details
    the markup that you are likely to want to use, or that is already
    in use.</para>

  <para>These markup languages contain a large number of elements, and
    it can be confusing sometimes to know which element to use for a
    particular situation.  This section goes through the elements you
    are most likely to need, and gives examples of how you would use
    them.</para>

  <para>This is <emphasis>not</emphasis> an exhaustive list of
    elements, since that would just reiterate the documentation for
    each language.  The aim of this section is to list those elements
    more likely to be useful to you.  If you have a question about how
    best to markup a particular piece of content, please post it to
    the &a.doc;.</para>

  <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 id="xml-markup-xhtml">
    <title>XHTML</title>

    <para>XHTML is the XML version of the HyperText Markup Language,
      which is 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>XHTML is used to markup pages on the FreeBSD web site.  It
      should not (generally) be used to mark up other documentation,
      since DocBook offers a far richer set of elements to choose
      from.  Consequently, you will normally only encounter XHTML pages
      if you are writing for the web site.</para>

    <para>HTML has gone through a number of versions, 1, 2, 3.0, 3.2,
      4.0 and then an XML-compliant version has also been created, which
      is called XHTML and the latest widespread version of it is
      XHTML 1.0(available in both
      <emphasis>strict</emphasis> and <emphasis>transitional</emphasis>
      variants).</para>

    <para>The XHTML DTDs are available from the Ports&nbsp;Collection
      in the <filename role="package">textproc/xhtml</filename> port.
      They are automatically installed as part of the <filename
	role="package">textproc/docproj</filename> port.</para>

    <sect2>
      <title>Formal Public Identifier (FPI)</title>

      <para>There are a number of XHTML FPIs, depending upon the
	version (also known as the level) of XHTML that you want to
	declare your document to be compliant with.</para>

      <para>The majority of XHTML documents on the FreeBSD web site
	comply with the transitional version of XHTML 1.0.</para>

      <programlisting>PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"</programlisting>
    </sect2>

    <sect2>
      <title>Sectional Elements</title>

      <para>An XHTML 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 XHTML Document Structure</title>

	<programlisting>&lt;html xmlns="http://www.w3.org/1999/xhtml">
  &lt;head>
	  &lt;title><replaceable>The Document's Title</replaceable>&lt;/title>
  &lt;/head>

  &lt;body>

    &hellip;

  &lt;/body>
&lt;/html></programlisting>
      </example>
    </sect2>

    <sect2>
      <title>Block Elements</title>

      <sect3>
	<title>Headings</title>

	<para>XHTML allows you to denote headings in your 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>Use:</para>

	  <programlisting>&lt;h1&gt;First section&lt;/h1&gt;

&lt;!&hyphen;- Document introduction goes here -&hyphen;&gt;

&lt;h2&gt;This is the heading for the first section&lt;/h2&gt;

&lt;!&hyphen;- Content for the first section goes here -&hyphen;&gt;

&lt;h3&gt;This is the heading for the first sub-section&lt;/h3&gt;

&lt;!&hyphen;- Content for the first sub-section goes here -&hyphen;&gt;

&lt;h2&gt;This is the heading for the second section&lt;/h2&gt;

&lt;!&hyphen;- Content for the second section goes here -&hyphen;&gt;</programlisting>
	</example>

	<para>Generally, an XHTML 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>Use:</para>

	  <programlisting>&lt;h1&gt;First section&lt;/h1&gt;

&lt;!&hyphen;- Document introduction -&hyphen;&gt;

&lt;h3&gt;Sub-section&lt;/h3&gt;

&lt;!&hyphen;- This is bad, &lt;h2&gt; has been left out -&hyphen;&gt;</programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Paragraphs</title>

	<para>XHTML supports a single paragraph element,
	  <sgmltag>p</sgmltag>.</para>

	<example>
	  <title><sgmltag>p</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<p>This is a paragraph.  It can contain just about any
  other element.</p>]]></programlisting>
	</example>
      </sect3>

      <sect3>
	<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>Use:</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>
      </sect3>

      <sect3>
	<title>Lists</title>

	<para>You 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>Use:</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>Use:</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>
      </sect3>

      <sect3>
	<title>Pre-formatted Text</title>

	<para>You can indicate that text should 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>You could use <sgmltag>pre</sgmltag> 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

    &lt;URL:http://people.FreeBSD.org/~nik/primer/index.html&gt;

  Comments appreciated.

  N</pre>]]></programlisting>

	  <para>Keep in mind that <literal>&lt;</literal> and
	    <literal>&amp;</literal> still are recognized as special
	    characters in pre-formatted text.  This is why the example
	    shown had to use <literal>&amp;lt;</literal> instead of
	    <literal>&lt;</literal>.  For consistency,
	    <literal>&amp;gt;</literal> was used in place of
	    <literal>&gt;</literal>, too.  Watch out for the special
	    characters that may appear in text copied from a
	    plain-text source, e.g., an email message or program
	    code.</para>
	</example>
      </sect3>

      <sect3>
	<title>Tables</title>

	<note>
	  <para>Most text-mode browsers (such as Lynx) do not render
	    tables particularly effectively.  If you are relying on
	    the tabular display of your content, you should consider
	    using alternative markup to prevent confusion.</para>
	</note>

	<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 you do not need to include the
	  <sgmltag>p</sgmltag> element.</para>

	<example>
	  <title>Simple Use of <sgmltag>table</sgmltag></title>

	  <para>Use:</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>Use:</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>Use:</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>Use:</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>
    <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>
      </sect3>
    </sect2>

    <sect2>
      <title>In-line Elements</title>

      <sect3>
	<title>Emphasizing Information</title>

	<para>You have two levels of emphasis available in XHTML,
	  <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 you should not rely on
	  it.  According to best practices, webpages only hold
	  structural and semantical information and stylesheets are
	  later applied to use these two so you should think of
	  semantics not formatting when using these tags.</para>

	<example>
	  <title><sgmltag>em</sgmltag> and
	    <sgmltag>strong</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<p><em>This</em> has been emphasized, while
  <strong>this</strong> has been strongly emphasized.</p>]]></programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Indicating Fixed-Pitch Text</title>

	<para>If you have content that should be rendered in a fixed
	  pitch (typewriter) typeface, use <sgmltag>tt</sgmltag> (for
	  <quote>teletype</quote>).</para>

	<example>
	  <title><sgmltag>tt</sgmltag></title>

	  <para>Use:</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>
      </sect3>
    </sect2>

    <sect2>
      <title>Links</title>

      <note>
	<para>Links are also inline elements.</para>
      </note>

      <sect3>
	<title>Linking to Other Documents on the WWW</title>

	<para>In order to include a link to another document on the
	  WWW you must know the URL of the document you want to link
	  to.</para>

	<para>The link is indicated with <sgmltag>a</sgmltag>, and the
	  <literal>href</literal> attribute contains the URL of the
	  target document.  The content of the element becomes the
	  link, and is normally indicated to the user in some way
	  (underlining, change of color, different mouse cursor when
	  over the link, and so on).</para>

	<example>
	  <title>Using <literal>&lt;a href="..."&gt;</literal></title>

	  <para>Use:</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>
	<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
	  anchors that you can link to.</para>

	<para>Anchors are indicated with <sgmltag>a</sgmltag> and the
	  <literal>id</literal> attribute instead of
	  <literal>href</literal>.</para>

	<example>
	  <title>Using <literal>&lt;a id="..."&gt;</literal></title>

	  <para>Use:</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 id 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>

  <sect1 id="xml-markup-docbook">
    <title>DocBook</title>

    <para>DocBook was originally developed by HaL Computer Systems and
      O'Reilly &amp; Associates to be a DTD for writing technical
      documentation <footnote><para>A short history can be found under
	  <ulink
	    url="http://www.oasis-open.org/docbook/intro.shtml#d0e41">
	    http://www.oasis-open.org/docbook/intro.shtml#d0e41</ulink>.</para></footnote>.
      Since 1998 it is maintained by the <ulink
	url="http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=docbook">
	DocBook Technical Committee</ulink>.  As such, and unlike
      LinuxDoc and XHTML, DocBook is very heavily oriented towards
      markup that describes <emphasis>what</emphasis> something is,
      rather than describing <emphasis>how</emphasis> it should be
      presented.</para>

    <note>
      <title>Formal Versus Informal</title>

      <para>Some elements may exist in two forms,
	<emphasis>formal</emphasis> and <emphasis>informal</emphasis>.
	Typically, the formal version of the element will consist of a
	title followed by the informal version of the element.  The
	informal version will not have a title.</para>
    </note>

    <para>The DocBook DTD is available from the Ports&nbsp;Collection
      in the <filename role="package">textproc/docbook-xml-450</filename>
      port.  It is automatically installed as part of the <filename
	role="package">textproc/docproj</filename> port.</para>

    <sect2>
      <title>&os; Extensions</title>

      <para>The FreeBSD Documentation Project has extended the DocBook
	DTD by adding some new elements.  These elements serve to make
	some of the markup more precise.</para>

      <para>Where a FreeBSD specific element is listed below it is
	clearly marked.</para>

      <para>Throughout the rest of this document, the term
	<quote>DocBook</quote> is used to mean the FreeBSD extended
	DocBook DTD.</para>

      <note>
	<para>There is nothing about these extensions that is FreeBSD
	  specific, it was just felt that they were useful
	  enhancements for this particular project.  Should anyone
	  from any of the other *nix camps (NetBSD, OpenBSD, Linux,
	  &hellip;) be interested in collaborating on a standard
	  DocBook extension set, please get in touch with
	  &a.doceng;.</para>
      </note>

      <para>The &os; extensions are not (currently) in the
	Ports&nbsp;Collection.  They are stored in the &os; Subversion
	tree, as <ulink
	  url="http://svnweb.FreeBSD.org/doc/head/share/xml/freebsd.dtd">head/share/xml/freebsd.dtd</ulink>.</para>
    </sect2>

    <sect2>
      <title>Formal Public Identifier (FPI)</title>

      <para>In compliance with the DocBook guidelines for writing FPIs
	for DocBook customizations, the FPI for the FreeBSD extended
	DocBook DTD is:</para>

	<programlisting>PUBLIC "-//FreeBSD//DTD DocBook V4.2-Based Extension//EN"</programlisting>
    </sect2>

    <sect2>
      <title>Document Structure</title>

      <para>DocBook allows you to structure your documentation in
	several ways.  In the FreeBSD Documentation Project we are
	using two primary types of DocBook document: the book and the
	article.</para>

      <para>A book is organized into <sgmltag>chapter</sgmltag>s.
	This is a mandatory requirement.  There may be
	<sgmltag>part</sgmltag>s between the book and the chapter to
	provide another layer of organization.  For example, the
	Handbook is arranged in this way.</para>

      <para>A chapter may (or may not) contain one or more sections.
	These are indicated with the <sgmltag>sect1</sgmltag> element.
	If a section contains another section then use the
	<sgmltag>sect2</sgmltag> element, and so on, up to
	<sgmltag>sect5</sgmltag>.</para>

      <para>Chapters and sections contain the remainder of the
	content.</para>

      <para>An article is simpler than a book, and does not use
	chapters.  Instead, the content of an article is organized
	into one or more sections, using the same
	<sgmltag>sect1</sgmltag> (and <sgmltag>sect2</sgmltag> and so
	on) elements that are used in books.</para>

      <para>Obviously, you should consider the nature of the
	documentation you are writing in order to decide whether it is
	best marked up as a book or an article.  Articles are well
	suited to information that does not need to be broken down
	into several chapters, and that is, relatively speaking, quite
	short, at up to 20-25 pages of content.  Books are best suited
	to information that can be broken up into several chapters,
	possibly with appendices and similar content as well.</para>

      <para>The <ulink url="&url.base;/docs.html">FreeBSD
	  tutorials</ulink> are all marked up as articles, while this
	document, the
	<ulink url="&url.books.faq;/index.html">FreeBSD FAQ</ulink>,
	and the <ulink url="&url.books.handbook;/index.html">FreeBSD
	  Handbook</ulink> are all marked up as books, for
	example.</para>

      <sect3>
	<title>Starting a Book</title>

	<para>The content of the book is contained within the
	  <sgmltag>book</sgmltag> element.  As well as containing
	  structural markup, this element can contain elements that
	  include additional information about the book.  This is
	  either meta-information, used for reference purposes, or
	  additional content used to produce a title page.</para>

	<para>This additional information should be contained within
	  <sgmltag>bookinfo</sgmltag>.</para>

	<example>
	  <title>Boilerplate <sgmltag>book</sgmltag> with
	    <sgmltag>bookinfo</sgmltag></title>

	  <!-- Can't put this in a marked section because of the
               replaceable elements -->

	  <programlisting>&lt;book>
  &lt;bookinfo>
    &lt;title><replaceable>Your Title Here</replaceable>&lt;/title>

    &lt;author>
      &lt;firstname><replaceable>Your first name</replaceable>&lt;/firstname>
      &lt;surname><replaceable>Your surname</replaceable>&lt;/surname>
      &lt;affiliation>
        &lt;address>&lt;email><replaceable>Your email address</replaceable>&lt;/email>&lt;/address>
      &lt;/affiliation>
    &lt;/author>

    &lt;copyright>
      &lt;year><replaceable>1998</replaceable>&lt;/year>
      &lt;holder role="mailto:<replaceable>your email address</replaceable>"><replaceable>Your name</replaceable>&lt;/holder>
    &lt;/copyright>

    &lt;releaseinfo>&#36;FreeBSD&#36;&lt;/releaseinfo>

    &lt;abstract>
      &lt;para><replaceable>Include an abstract of the book's contents here.</replaceable>&lt;/para>
    &lt;/abstract>
  &lt;/bookinfo>

  &hellip;

&lt;/book></programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Starting an Article</title>

	<para>The content of the article is contained within the
	  <sgmltag>article</sgmltag> element.  As well as containing
	  structural markup, this element can contain elements that
	  include additional information about the article.  This is
	  either meta-information, used for reference purposes, or
	  additional content used to produce a title page.</para>

	<para>This additional information should be contained within
	  <sgmltag>articleinfo</sgmltag>.</para>

	<example>
	  <title>Boilerplate <sgmltag>article</sgmltag> with
	    <sgmltag>articleinfo</sgmltag></title>

	  <!-- Can't put this in a marked section because of the
               replaceable elements -->

	  <programlisting>&lt;article>
  &lt;articleinfo>
    &lt;title><replaceable>Your title here</replaceable>&lt;/title>

    &lt;author>
      &lt;firstname><replaceable>Your first name</replaceable>&lt;/firstname>
      &lt;surname><replaceable>Your surname</replaceable>&lt;/surname>
      &lt;affiliation>
        &lt;address>&lt;email><replaceable>Your email address</replaceable>&lt;/email>&lt;/address>
      &lt;/affiliation>
    &lt;/author>

    &lt;copyright>
      &lt;year><replaceable>1998</replaceable>&lt;/year>
      &lt;holder role="mailto:<replaceable>your email address</replaceable>"><replaceable>Your name</replaceable>&lt;/holder>
    &lt;/copyright>

    &lt;releaseinfo>&#36;FreeBSD&#36;&lt;/releaseinfo>

    &lt;abstract>
      &lt;para><replaceable>Include an abstract of the article's contents here.</replaceable>&lt;/para>
    &lt;/abstract>
  &lt;/articleinfo>

  &hellip;

&lt;/article></programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Indicating Chapters</title>

	<para>Use <sgmltag>chapter</sgmltag> to mark up your chapters.
	  Each chapter has a mandatory <sgmltag>title</sgmltag>.
	  Articles do not contain chapters, they are reserved for
	  books.</para>

	<example>
	  <title>A Simple Chapter</title>

	  <programlisting><![CDATA[<chapter>
  <title>The Chapter's Title</title>

  ...
</chapter>]]></programlisting>
	</example>

	<para>A chapter cannot be empty; it must contain elements in
	  addition to <sgmltag>title</sgmltag>.  If you need to
	  include an empty chapter then just use an empty
	  paragraph.</para>

	<example>
	  <title>Empty Chapters</title>

	  <programlisting><![CDATA[<chapter>
  <title>This is An Empty Chapter</title>

  <para></para>
</chapter>]]></programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Sections Below Chapters</title>

	<para>In books, chapters may (but do not need to) be broken up
	  into sections, subsections, and so on.  In articles,
	  sections are the main structural element, and each article
	  must contain at least one section.  Use the
	  <sgmltag>sect<replaceable>n</replaceable></sgmltag> element.
	  The <replaceable>n</replaceable> indicates the section
	  number, which identifies the section level.</para>

	<para>The first
	  <sgmltag>sect<replaceable>n</replaceable></sgmltag> is
	  <sgmltag>sect1</sgmltag>.  You can have one or more of these
	  in a chapter.  They can contain one or more
	  <sgmltag>sect2</sgmltag> elements, and so on, down to
	  <sgmltag>sect5</sgmltag>.</para>

	<example>
	  <title>Sections in Chapters</title>

	  <programlisting><![CDATA[<chapter>
  <title>A Sample Chapter</title>

  <para>Some text in the chapter.</para>

  <sect1>
    <title>First Section (1.1)</title>

    &hellip;
  </sect1>

  <sect1>
    <title>Second Section (1.2)</title>

    <sect2>
      <title>First Sub-Section (1.2.1)</title>

      <sect3>
        <title>First Sub-Sub-Section (1.2.1.1)</title>

        &hellip;
      </sect3>
    </sect2>

    <sect2>
      <title>Second Sub-Section (1.2.2)</title>

      &hellip;
    </sect2>
  </sect1>
</chapter>]]></programlisting>
	</example>

	<note>
	  <para>This example includes section numbers in the section
	    titles.  You should not do this in your documents.  Adding
	    the section numbers is carried out by the stylesheets (of
	    which more later), and you do not need to manage them
	    yourself.</para>
	</note>
      </sect3>

      <sect3>
	<title>Subdividing Using <sgmltag>part</sgmltag>
	  Elements</title>

	<para>You can introduce another layer of organization between
	  <sgmltag>book</sgmltag> and <sgmltag>chapter</sgmltag> with
	  one or more <sgmltag>part</sgmltag>s.  This cannot be done
	  in an <sgmltag>article</sgmltag>.</para>

	<programlisting><![CDATA[<part>
  <title>Introduction</title>

  <chapter>
    <title>Overview</title>

    ...
  </chapter>

  <chapter>
    <title>What is FreeBSD?</title>

    ...
  </chapter>

  <chapter>
    <title>History</title>

    ...
  </chapter>
</part>]]></programlisting>
      </sect3>
    </sect2>

    <sect2>
      <title>Block Elements</title>

      <sect3>
	<title>Paragraphs</title>

	<para>DocBook supports three types of paragraphs:
	  <sgmltag>formalpara</sgmltag>, <sgmltag>para</sgmltag>, and
	  <sgmltag>simpara</sgmltag>.</para>

	<para>Most of the time you will only need to use
	  <sgmltag>para</sgmltag>.  <sgmltag>formalpara</sgmltag>
	  includes a <sgmltag>title</sgmltag> element, and
	  <sgmltag>simpara</sgmltag> disallows some elements from
	  within <sgmltag>para</sgmltag>.  Stick with
	  <sgmltag>para</sgmltag>.</para>

	<example>
	  <title><sgmltag>para</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>This is a paragraph.  It can contain just about any
  other element.</para> ]]></programlisting>

	  <para>Appearance:</para>

	  <para>This is a paragraph.  It can contain just about any
	    other element.</para>
	</example>
      </sect3>

      <sect3>
	<title>Block Quotations</title>

	<para>A block quotation is an extended quotation from another
	  document that should not appear within the current
	  paragraph.  You will probably only need it
	  infrequently.</para>

	<para>Blockquotes can optionally contain a title and an
	  attribution (or they can be left untitled and
	  unattributed).</para>

	<example>
	  <title><sgmltag>blockquote</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>A small excerpt from the US Constitution:</para>

<blockquote>
  <title>Preamble to the Constitution of the United States</title>

  <attribution>Copied from a web site somewhere</attribution>

  <para>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.</para>
</blockquote>]]></programlisting>

	  <para>Appearance:</para>

	  <para>A small excerpt from the US Constitution:</para>

	  <blockquote>
	    <title>Preamble to the Constitution of the United
	      States</title>

	    <attribution>Copied from a web site
	      somewhere</attribution>

	    <para>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.</para>
	  </blockquote>
	</example>
      </sect3>

      <sect3>
	<title>Tips, Notes, Warnings, Cautions, Important Information
	  and Sidebars</title>

	<para>You may need to include extra information separate from
	  the main body of the text.  Typically this is
	  <quote>meta</quote> information that the user should be
	  aware of.</para>

	<para>Depending on the nature of the information, one of
	  <sgmltag>tip</sgmltag>, <sgmltag>note</sgmltag>,
	  <sgmltag>warning</sgmltag>, <sgmltag>caution</sgmltag>, and
	  <sgmltag>important</sgmltag> should be used.  Alternatively,
	  if the information is related to the main text but is not
	  one of the above, use <sgmltag>sidebar</sgmltag>.</para>

	<para>The circumstances in which to choose one of these
	  elements over another is unclear.  The DocBook documentation
	  suggests:</para>

	<itemizedlist>
	  <listitem>
	    <para>A Note is for information that should be heeded by
	      all readers.</para>
	  </listitem>

	  <listitem>
	    <para>An Important element is a variation on Note.</para>
	  </listitem>

	  <listitem>
	    <para>A Caution is for information regarding possible data
	      loss or software damage.</para>
	  </listitem>

	  <listitem>
	    <para>A Warning is for information regarding possible
	      hardware damage or injury to life or limb.</para>
	  </listitem>
	</itemizedlist>

	<example>
	  <title><sgmltag>warning</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<warning>
  <para>Installing FreeBSD may make you want to delete Windows from your
    hard disk.</para>
</warning>]]></programlisting>
	</example>

	<para>Appearance:</para>
	<!-- Need to do this outside of the example -->
	<warning>
	  <para>Installing FreeBSD may make you want to delete Windows
	    from your hard disk.</para>
	</warning>
      </sect3>

      <sect3>
	<title>Lists and Procedures</title>

	<para>You will often need to list pieces of information to the
	  user, or present them with a number of steps that must be
	  carried out in order to accomplish a particular goal.</para>

	<para>In order to do this, use
	  <sgmltag>itemizedlist</sgmltag>,
	  <sgmltag>orderedlist</sgmltag>, or
	  <sgmltag>procedure</sgmltag><footnote><para>There are other
	      types of list element in DocBook, but we are not
	      concerned with those at the
	      moment.</para></footnote></para>

	<para><sgmltag>itemizedlist</sgmltag> and
	  <sgmltag>orderedlist</sgmltag> are similar to their
	  counterparts in HTML, <sgmltag>ul</sgmltag> and
	  <sgmltag>ol</sgmltag>.  Each one consists of one or more
	  <sgmltag>listitem</sgmltag> elements, and each
	  <sgmltag>listitem</sgmltag> contains one or more block
	  elements.  The <sgmltag>listitem</sgmltag> elements are
	  analogous to HTML's <sgmltag>li</sgmltag> tags.  However,
	  unlike HTML, they are required.</para>

	<para><sgmltag>procedure</sgmltag> is slightly different.  It
	  consists of <sgmltag>step</sgmltag>s, which may in turn
	  consists of more <sgmltag>step</sgmltag>s or
	  <sgmltag>substep</sgmltag>s.  Each <sgmltag>step</sgmltag>
	  contains block elements.</para>

	<example>
	  <title><sgmltag>itemizedlist</sgmltag>,
	    <sgmltag>orderedlist</sgmltag>, and
	    <sgmltag>procedure</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<itemizedlist>
  <listitem>
    <para>This is the first itemized item.</para>
  </listitem>

  <listitem>
    <para>This is the second itemized item.</para>
  </listitem>
</itemizedlist>

<orderedlist>
  <listitem>
    <para>This is the first ordered item.</para>
  </listitem>

  <listitem>
    <para>This is the second ordered item.</para>
  </listitem>
</orderedlist>

<procedure>
  <step>
    <para>Do this.</para>
  </step>

  <step>
    <para>Then do this.</para>
  </step>

  <step>
    <para>And now do this.</para>
  </step>
</procedure>]]></programlisting>

	  <para>Appearance:</para>

	  <itemizedlist>
	    <listitem>
	      <para>This is the first itemized item.</para>
	    </listitem>

	    <listitem>
	      <para>This is the second itemized item.</para>
	    </listitem>
	  </itemizedlist>

	  <orderedlist>
	    <listitem>
	      <para>This is the first ordered item.</para>
	    </listitem>

	    <listitem>
	      <para>This is the second ordered item.</para>
	    </listitem>
	  </orderedlist>
	</example>

	<!-- Can't have <procedure> inside <example>, so this is a cheat -->

	<procedure>
	  <step>
	    <para>Do this.</para>
	  </step>

	  <step>
	    <para>Then do this.</para>
	  </step>

	  <step>
	    <para>And now do this.</para>
	  </step>
	</procedure>
      </sect3>

      <sect3>
	<title>Showing File Samples</title>

	<para>If you want to show a fragment of a file (or perhaps a
	  complete file) to the user, wrap it in the
	  <sgmltag>programlisting</sgmltag> element.</para>

	<para>White space and line breaks within
	  <sgmltag>programlisting</sgmltag> <emphasis>are</emphasis>
	  significant.  In particular, this means that the opening tag
	  should appear on the same line as the first line of the
	  output, and the closing tag should appear on the same line
	  as the last line of the output, otherwise spurious blank
	  lines may be included.</para>

	<example>
	  <title><sgmltag>programlisting</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>When you have finished, your program should look like
  this:</para>

<programlisting>#include &lt;stdio.h&gt;

int
main(void)
{
    printf("hello, world\n");
}</programlisting>]]></programlisting>

	  <para>Notice how the angle brackets in the
	    <literal>#include</literal> line need to be referenced by
	    their entities instead of being included literally.</para>

	  <para>Appearance:</para>

	  <para>When you have finished, your program should look like
	    this:</para>

	  <programlisting>#include &lt;stdio.h&gt;

int
main(void)
{
    printf("hello, world\n");
}</programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Callouts</title>

	<para>A callout is a mechanism for referring back to an
	  earlier piece of text or specific position within an earlier
	  example without linking to it within the text.</para>

	<para>To do this, mark areas of interest in your example
	  (<sgmltag>programlisting</sgmltag>,
	  <sgmltag>literallayout</sgmltag>, or whatever) with the
	  <sgmltag>co</sgmltag> element.  Each element must have a
	  unique <literal>id</literal> assigned to it.  After the
	  example include a <sgmltag>calloutlist</sgmltag> that refers
	  back to the example and provides additional
	  commentary.</para>

	<example>
	  <title><sgmltag>co</sgmltag> and
	    <sgmltag>calloutlist</sgmltag></title>

	  <programlisting><![CDATA[<para>When you have finished, your program should look like
  this:</para>

<programlisting>#include &lt;stdio.h&gt; <co id="co-ex-include"/>

int <co id="co-ex-return"/>
main(void)
{
    printf("hello, world\n"); <co id="co-ex-printf"/>
}</programlisting>

<calloutlist>
  <callout arearefs="co-ex-include">
    <para>Includes the standard IO header file.</para>
  </callout>

  <callout arearefs="co-ex-return">
    <para>Specifies that <function>main()</function> returns an
      int.</para>
  </callout>

  <callout arearefs="co-ex-printf">
    <para>The <function>printf()</function> call that writes
      <literal>hello, world</literal> to standard output.</para>
  </callout>
</calloutlist>]]></programlisting>

	  <para>Appearance:</para>

	  <para>When you have finished, your program should look like
	    this:</para>

	  <programlisting>#include &lt;stdio.h&gt; <co id="co-ex-include"/>

int <co id="co-ex-return"/>
main(void)
{
    printf("hello, world\n"); <co id="co-ex-printf"/>
}</programlisting>

	  <calloutlist>
	    <callout arearefs="co-ex-include">
	      <para>Includes the standard IO header file.</para>
	    </callout>

	    <callout arearefs="co-ex-return">
	      <para>Specifies that <function>main()</function> returns
		an int.</para>
	    </callout>

	    <callout arearefs="co-ex-printf">
	      <para>The <function>printf()</function> call that writes
		<literal>hello, world</literal> to standard
		output.</para>
	    </callout>
	  </calloutlist>
	</example>
      </sect3>

      <sect3>
	<title>Tables</title>

	<para>Unlike HTML, you do not need to use tables for layout
	  purposes, as the stylesheet handles those issues for you.
	  Instead, just use tables for marking up tabular data.</para>

	<para>In general terms (and see the DocBook documentation for
	  more detail) a table (which can be either formal or
	  informal) consists of a <sgmltag>table</sgmltag> element.
	  This contains at least one <sgmltag>tgroup</sgmltag>
	  element, which specifies (as an attribute) the number of
	  columns in this table group.  Within the tablegroup you can
	  then have one <sgmltag>thead</sgmltag> element, which
	  contains elements for the table headings (column headings),
	  and one <sgmltag>tbody</sgmltag> which contains the body of
	  the table.</para>

	<para>Both <sgmltag>tgroup</sgmltag> and
	  <sgmltag>thead</sgmltag> contain <sgmltag>row</sgmltag>
	  elements, which in turn contain <sgmltag>entry</sgmltag>
	  elements.  Each <sgmltag>entry</sgmltag> element specifies
	  one cell in the table.</para>

	<example>
	  <title><sgmltag>informaltable</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<informaltable pgwide="1">
  <tgroup cols="2">
    <thead>
      <row>
        <entry>This is Column Head 1</entry>
        <entry>This is Column Head 2</entry>
      </row>
    </thead>

    <tbody>
      <row>
        <entry>Row 1, column 1</entry>
        <entry>Row 1, column 2</entry>
      </row>

      <row>
        <entry>Row 2, column 1</entry>
        <entry>Row 2, column 2</entry>
      </row>
    </tbody>
  </tgroup>
</informaltable>]]></programlisting>

	  <para>Appearance:</para>

	  <informaltable pgwide="1">
	    <tgroup cols="2">
	      <thead>
		<row>
		  <entry>This is Column Head 1</entry>
		  <entry>This is Column Head 2</entry>
		</row>
	      </thead>

	      <tbody>
		<row>
		  <entry>Row 1, column 1</entry>
		  <entry>Row 1, column 2</entry>
		</row>

		<row>
		  <entry>Row 2, column 1</entry>
		  <entry>Row 2, column 2</entry>
		</row>
	      </tbody>
	    </tgroup>
	  </informaltable>
	</example>

	<para>Always use the <literal>pgwide</literal> attribute with
	  a value of <literal>1</literal> with the
	  <sgmltag>informaltable</sgmltag> element.  A bug in Internet
	  Explorer can cause the table to render incorrectly if this
	  is omitted.</para>

	<para>If you do not want a border around the table the
	  <literal>frame</literal> attribute can be added to the
	  <sgmltag>informaltable</sgmltag> element with a value of
	  <literal>none</literal> (i.e., <literal>&lt;informaltable
	    frame="none"&gt;</literal>).</para>

	<example>
	  <title>Tables Where <literal>frame="none"</literal></title>

	  <para>Appearance:</para>

	  <informaltable frame="none" pgwide="1">
	    <tgroup cols="2">
	      <thead>
		<row>
		  <entry>This is Column Head 1</entry>
		  <entry>This is Column Head 2</entry>
		</row>
	      </thead>

	      <tbody>
		<row>
		  <entry>Row 1, column 1</entry>
		  <entry>Row 1, column 2</entry>
		</row>

		<row>
		  <entry>Row 2, column 1</entry>
		  <entry>Row 2, column 2</entry>
		</row>
	      </tbody>
	    </tgroup>
	  </informaltable>
	</example>
      </sect3>

      <sect3>
	<title>Examples for the User to Follow</title>

	<para>A lot of the time you need to show examples for the user
	  to follow.  Typically, these will consist of dialogs with
	  the computer; the user types in a command, the user gets a
	  response back, they type in another command, and so
	  on.</para>

	<para>A number of distinct elements and entities come into
	  play here.</para>

	<variablelist>
	  <varlistentry>
	    <term><sgmltag>screen</sgmltag></term>

	    <listitem>
	      <para>Everything the user sees in this example will be
		on the computer screen, so the next element is
		<sgmltag>screen</sgmltag>.</para>

	      <para>Within <sgmltag>screen</sgmltag>, white space is
		significant.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><sgmltag>prompt</sgmltag>,
	      <literal>&amp;prompt.root;</literal> and
	      <literal>&amp;prompt.user;</literal></term>

	    <listitem>
	      <para>Some of the things the user will be seeing on the
		screen are prompts from the computer (either from the
		operating system, command shell, or application).
		These should be marked up using
		<sgmltag>prompt</sgmltag>.</para>

	      <para>As a special case, the two shell prompts for the
		normal user and the root user have been provided as
		entities.  Every time you want to indicate the user is
		at a shell prompt, use one of
		<literal>&amp;prompt.root;</literal> and
		<literal>&amp;prompt.user;</literal> as necessary.
		They do not need to be inside
		<sgmltag>prompt</sgmltag>.</para>

	      <note>
		<para><literal>&amp;prompt.root;</literal> and
		  <literal>&amp;prompt.user;</literal> are FreeBSD
		  extensions to DocBook, and are not part of the
		  original DTD.</para>
	      </note>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><sgmltag>userinput</sgmltag></term>

	    <listitem>
	      <para>When displaying text that the user should type in,
		wrap it in <sgmltag>userinput</sgmltag> tags.  It will
		probably be displayed differently to the user.</para>
	    </listitem>
	  </varlistentry>
	</variablelist>

	<example>
	  <title><sgmltag>screen</sgmltag>, <sgmltag>prompt</sgmltag>,
	    and <sgmltag>userinput</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<screen>&prompt.user; <userinput>ls -1</userinput>
foo1
foo2
foo3
&prompt.user; <userinput>ls -1 | grep foo2</userinput>
foo2
&prompt.user; <userinput>su</userinput>
<prompt>Password: </prompt>
&prompt.root; <userinput>cat foo2</userinput>
This is the file called 'foo2'</screen>]]></programlisting>

	  <para>Appearance:</para>

	  <screen>&prompt.user; <userinput>ls -1</userinput>
foo1
foo2
foo3
&prompt.user; <userinput>ls -1 | grep foo2</userinput>
foo2
&prompt.user; <userinput>su</userinput>
<prompt>Password: </prompt>
&prompt.root; <userinput>cat foo2</userinput>
This is the file called 'foo2'</screen>
	</example>

	<note>
	  <para>Even though we are displaying the contents of the file
	    <filename>foo2</filename>, it is <emphasis>not</emphasis>
	    marked up as <sgmltag>programlisting</sgmltag>.  Reserve
	    <sgmltag>programlisting</sgmltag> for showing fragments of
	    files outside the context of user actions.</para>
	</note>
      </sect3>
    </sect2>

    <sect2>
      <title>In-line Elements</title>

      <sect3>
	<title>Emphasizing Information</title>

	<para>When you want to emphasize a particular word or phrase,
	  use <sgmltag>emphasis</sgmltag>.  This may be presented as
	  italic, or bold, or might be spoken differently with a
	  text-to-speech system.</para>

	<para>There is no way to change the presentation of the
	  emphasis within your document, no equivalent of HTML's
	  <sgmltag>b</sgmltag> and <sgmltag>i</sgmltag>.  If the
	  information you are presenting is important then consider
	  presenting it in <sgmltag>important</sgmltag> rather than
	  <sgmltag>emphasis</sgmltag>.</para>

	<example>
	  <title><sgmltag>emphasis</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>FreeBSD is without doubt <emphasis>the</emphasis>
  premiere Unix like operating system for the Intel architecture.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>FreeBSD is without doubt <emphasis>the</emphasis>
	    premiere Unix like operating system for the Intel
	    architecture.</para>
	</example>
      </sect3>

      <sect3>
	<title>Quotations</title>

	<para>To quote text from another document or source, or to
	  denote a phrase that is used figuratively, use
	  <sgmltag>quote</sgmltag>.  Within a <sgmltag>quote</sgmltag>
	  tag, you may use most of the markup tags available for
	  normal text.</para>

	<example>
	  <title>Quotations</title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>However, make sure that the search does not go beyond the
  <quote>boundary between local and public administration</quote>,
  as RFC 1535 calls it.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>However, make sure that the search does not go beyond
	    the <quote>boundary between local and public
	      administration</quote>, as RFC 1535 calls it.</para>
	</example>
      </sect3>

      <sect3>
	<title>Keys, Mouse Buttons, and Combinations</title>

	<para>To refer to a specific key on the keyboard, use
	  <sgmltag>keycap</sgmltag>.  To refer to a mouse button, use
	  <sgmltag>mousebutton</sgmltag>.  And to refer to
	  combinations of key presses or mouse clicks, wrap them all
	  in <sgmltag>keycombo</sgmltag>.</para>

	<para><sgmltag>keycombo</sgmltag> has an attribute called
	  <literal>action</literal>, which may be one of
	  <literal>click</literal>, <literal>double-click</literal>,
	  <literal>other</literal>, <literal>press</literal>,
	  <literal>seq</literal>, or <literal>simul</literal>.  The
	  last two values denote whether the keys or buttons should be
	  pressed in sequence, or simultaneously.</para>

	<para>The stylesheets automatically add any connecting
	  symbols, such as <literal>+</literal>, between the key
	  names, when wrapped in <sgmltag>keycombo</sgmltag>.</para>

	<example>
	  <title>Keys, Mouse Buttons, and Combinations</title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>To switch to the second virtual terminal, press
  <keycombo action="simul"><keycap>Alt</keycap>
    <keycap>F1</keycap></keycombo>.</para>

<para>To exit <command>vi</command> without saving your work, type
  <keycombo action="seq"><keycap>Esc</keycap><keycap>:</keycap>
    <keycap>q</keycap><keycap>!</keycap></keycombo>.</para>

<para>My window manager is configured so that
  <keycombo action="simul"><keycap>Alt</keycap>
    <mousebutton>right</mousebutton>
  </keycombo> mouse button is used to move windows.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>To switch to the second virtual terminal, press
	    <keycombo action="simul"><keycap>Alt</keycap>
	      <keycap>F1</keycap></keycombo>.</para>

	  <para>To exit <command>vi</command> without saving your
	    work, type <keycombo action="seq">
	      <keycap>Esc</keycap>
	      <keycap>:</keycap>
	      <keycap>q</keycap>
	      <keycap>!</keycap></keycombo>.</para>

	  <para>My window manager is configured so that
	    <keycombo action="simul">
	      <keycap>Alt</keycap>
	      <mousebutton>right</mousebutton></keycombo> mouse button
	    is used to move windows.</para>
	</example>
      </sect3>

      <sect3>
	<title>Applications, Commands, Options, and Cites</title>

	<para>You will frequently want to refer to both applications
	  and commands when writing documentation.  The distinction
	  between them is simple: an application is the name for a
	  suite (or possibly just 1) of programs that fulfill a
	  particular task.  A command is the name of a program that
	  the user can run.</para>

	<para>In addition, you will occasionally need to list one or
	  more of the options that a command might take.</para>

	<para>Finally, you will often want to list a command with its
	  manual section number, in the <quote>command(number)</quote>
	  format so common in Unix manuals.</para>

	<para>Mark up application names with
	  <sgmltag>application</sgmltag>.</para>

	<para>When you want to list a command with its manual section
	  number (which should be most of the time) the DocBook
	  element is <sgmltag>citerefentry</sgmltag>.  This will
	  contain a further two elements,
	  <sgmltag>refentrytitle</sgmltag> and
	  <sgmltag>manvolnum</sgmltag>.  The content of
	  <sgmltag>refentrytitle</sgmltag> is the name of the command,
	  and the content of <sgmltag>manvolnum</sgmltag> is the
	  manual page section.</para>

	<para>This can be cumbersome to write, and so a series of
	  <link linkend="xml-primer-general-entities">general
	    entities</link> have been created to make this easier.
	  Each entity takes the form
	  <literal>&amp;man.<replaceable>manual-page</replaceable>.<replaceable>manual-section</replaceable>;</literal>.</para>

	<para>The file that contains these entities is in
	  <filename>doc/share/xml/man-refs.ent</filename>, and can be
	  referred to using this FPI:</para>

	<programlisting>PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN"</programlisting>

	<para>Therefore, the introduction to your documentation will
	  probably look like this:</para>

	<programlisting>&lt;!DOCTYPE book PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [

&lt;!ENTITY % man PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN"&gt;
%man;

&hellip;

]&gt;</programlisting>

	<para>Use <sgmltag>command</sgmltag> when you want to include
	  a command name <quote>in-line</quote> but present it as
	  something the user should type in.</para>

	<para>Use <sgmltag>option</sgmltag> to mark up the options
	  which will be passed to a command.</para>

	<para>When referring to the same command multiple times in
	  close proximity it is preferred to use the
	  <literal>&amp;man.<replaceable>command</replaceable>.<replaceable>section</replaceable>;</literal>
	  notation to markup the first reference and use
	  <sgmltag>command</sgmltag> to markup subsequent references.
	  This makes the generated output, especially HTML, appear
	  visually better.</para>

	<para>This can be confusing, and sometimes the choice is not
	  always clear.  Hopefully this example makes it
	  clearer.</para>

	<example>
	  <title>Applications, Commands, and Options</title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para><application>Sendmail</application> is the most
  widely used Unix mail application.</para>

<para><application>Sendmail</application> includes the
  <citerefentry>
    <refentrytitle>sendmail</refentrytitle>
    <manvolnum>8</manvolnum>
  </citerefentry>, &man.mailq.1;, and &man.newaliases.1;
  programs.</para>

<para>One of the command line parameters to <citerefentry>
    <refentrytitle>sendmail</refentrytitle>
    <manvolnum>8</manvolnum>
  </citerefentry>, <option>-bp</option>, will display the current
  status of messages in the mail queue.  Check this on the command
  line by running <command>sendmail -bp</command>.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para><application>Sendmail</application> is the most widely
	    used Unix mail application.</para>

	  <para><application>Sendmail</application> includes the
	    <citerefentry>
	      <refentrytitle>sendmail</refentrytitle>
	      <manvolnum>8</manvolnum>
	    </citerefentry>, &man.mailq.1;, and &man.newaliases.1;
	    programs.</para>

	  <para>One of the command line parameters to
	    <citerefentry>
	      <refentrytitle>sendmail</refentrytitle>
	      <manvolnum>8</manvolnum>
	    </citerefentry>, <option>-bp</option>, will display the
	    current status of messages in the mail queue.  Check this
	    on the command line by running
	    <command>sendmail -bp</command>.</para>
	</example>

	<note>
	  <para>Notice how the
	    <literal>&amp;man.<replaceable>command</replaceable>.<replaceable>section</replaceable>;</literal>
	    notation is easier to follow.</para>
	</note>
      </sect3>

      <sect3>
	<title>Files, Directories, Extensions</title>

	<para>Whenever you wish to refer to the name of a file, a
	  directory, or a file extension, use
	  <sgmltag>filename</sgmltag>.</para>

	<example>
	  <title><sgmltag>filename</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>The SGML source for the Handbook in English can be
  found in <filename class="directory">/usr/doc/en_US.ISO8859-1/books/handbook/</filename>.  The first
  file is called <filename>book.xml</filename> in that
  directory.  You should also see a <filename>Makefile</filename>
  and a number of files with a <filename>.ent</filename>
  extension.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>The SGML source for the Handbook in English can be
	    found in <filename>/usr/doc/en/handbook/</filename>.  The
	    first file is called <filename>handbook.xml</filename> in
	    that directory.  You should also see a
	    <filename>Makefile</filename> and a number of files with a
	    <filename>.ent</filename> extension.</para>
	</example>
      </sect3>

      <sect3>
	<title>The Name of Ports</title>

	<note>
	  <title>&os; Extension</title>

	  <para>These elements are part of the FreeBSD extension to
	    DocBook, and do not exist in the original DocBook
	    DTD.</para>
	</note>

	<para>You might need to include the name of a program from the
	  FreeBSD Ports Collection in the documentation.  Use the
	  <sgmltag>filename</sgmltag> tag with the
	  <literal>role</literal> attribute set to
	  <literal>package</literal> to identify these.  Since ports
	  can be installed in any number of locations, only include
	  the category and the port name; do not include
	  <filename>/usr/ports</filename>.</para>

	<example>
	  <title><sgmltag>filename</sgmltag> Tag with
	    <literal>package</literal> Role</title>

	  <para>Use:</para>

          <programlisting><![CDATA[<para>Install the <filename role="package">net/ethereal</filename> port to view network traffic.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>Install the <filename
	      role="package">net/ethereal</filename> port to view
	    network traffic.</para>
	</example>
      </sect3>

      <sect3>
	<title>Devices</title>

	<note>
	  <title>&os; Extension</title>

	  <para>These elements are part of the FreeBSD extension to
	    DocBook, and do not exist in the original DocBook
	    DTD.</para>
	</note>

	<para>When referring to devices you have two choices.  You can
	  either refer to the device as it appears in
	  <filename>/dev</filename>, or you can use the name of the
	  device as it appears in the kernel.  For this latter course,
	  use <sgmltag>devicename</sgmltag>.</para>

	<para>Sometimes you will not have a choice.  Some devices,
	  such as networking cards, do not have entries in
	  <filename>/dev</filename>, or the entries are markedly
	  different from those entries.</para>

	<example>
	  <title><sgmltag>devicename</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para><devicename>sio</devicename> is used for serial
  communication in FreeBSD.  <devicename>sio</devicename> manifests
  through a number of entries in <filename>/dev</filename>, including
  <filename>/dev/ttyd0</filename> and <filename>/dev/cuaa0</filename>.</para>

<para>By contrast, the networking devices, such as
  <devicename>ed0</devicename> do not appear in <filename>/dev</filename>.</para>

<para>In MS-DOS, the first floppy drive is referred to as
  <devicename>a:</devicename>.  In FreeBSD it is
  <filename>/dev/fd0</filename>.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para><devicename>sio</devicename> is used for serial
	    communication in FreeBSD.  <devicename>sio</devicename>
	    manifests through a number of entries in
	    <filename>/dev</filename>, including
	    <filename>/dev/ttyd0</filename> and
	    <filename>/dev/cuaa0</filename>.</para>

	  <para>By contrast, the networking devices, such as
	    <devicename>ed0</devicename> do not appear in
	    <filename>/dev</filename>.</para>

	  <para>In MS-DOS, the first floppy drive is referred to as
	    <devicename>a:</devicename>.  In FreeBSD it is
	    <filename>/dev/fd0</filename>.</para>
	</example>
      </sect3>

      <sect3>
	<title>Hosts, Domains, IP Addresses, and So Forth</title>

	<note>
	  <title>&os; Extension</title>

	  <para>These elements are part of the FreeBSD extension to
	    DocBook, and do not exist in the original DocBook
	    DTD.</para>
	</note>

	<para>You can markup identification information for networked
	  computers (hosts) in several ways, depending on the nature
	  of the information.  All of them use
	  <sgmltag>hostid</sgmltag> as the element, with the
	  <literal>role</literal> attribute selecting the type of the
	  marked up information.</para>

	<variablelist>
	  <varlistentry>
	    <term>No <literal>role</literal> attribute, or
	      <literal>role="hostname"</literal></term>

	    <listitem>
	      <para>With no <literal>role</literal> attribute (i.e.,
		<sgmltag>hostid</sgmltag>...<sgmltag>/hostid</sgmltag>)
		the marked up information is the simple hostname, such
		as <literal>freefall</literal> or
		<literal>wcarchive</literal>.  You can explicitly
		specify this with
		<literal>role="hostname"</literal>.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>role="domainname"</literal></term>

	    <listitem>
	      <para>The text is a domain name, such as
		<literal>FreeBSD.org</literal> or
		<literal>ngo.org.uk</literal>.  There is no hostname
		component.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>role="fqdn"</literal></term>

	    <listitem>
	      <para>The text is a Fully Qualified Domain Name, with
		both hostname and domain name parts.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>role="ipaddr"</literal></term>

	    <listitem>
	      <para>The text is an IP address, probably expressed as a
		dotted quad.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>role="ip6addr"</literal></term>

	    <listitem>
	      <para>The text is an IPv6 address.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>role="netmask"</literal></term>

	    <listitem>
	      <para>The text is a network mask, which might be
		expressed as a dotted quad, a hexadecimal string, or
		as a <literal>/</literal> followed by a number.</para>
	    </listitem>
	  </varlistentry>

	  <varlistentry>
	    <term><literal>role="mac"</literal></term>

	    <listitem>
	      <para>The text is an Ethernet MAC address, expressed as
		a series of 2 digit hexadecimal numbers separated by
		colons.</para>
	    </listitem>
	  </varlistentry>
	</variablelist>

	<example>
	  <title><sgmltag>hostid</sgmltag> and Roles</title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>The local machine can always be referred to by the
  name <hostid>localhost</hostid>, which will have the IP address
  <hostid role="ipaddr">127.0.0.1</hostid>.</para>

<para>The <hostid role="domainname">FreeBSD.org</hostid> domain
  contains a number of different hosts, including
  <hostid role="fqdn">freefall.FreeBSD.org</hostid> and
  <hostid role="fqdn">pointyhat.FreeBSD.org</hostid>.</para>

<para>When adding an IP alias to an interface (using
  <command>ifconfig</command>) <emphasis>always</emphasis> use a
  netmask of <hostid role="netmask">255.255.255.255</hostid>
  (which can also be expressed as <hostid
    role="netmask">0xffffffff</hostid>).</para>

<para>The MAC address uniquely identifies every network card
  in existence.  A typical MAC address looks like <hostid
    role="mac">08:00:20:87:ef:d0</hostid>.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>The local machine can always be referred to by the
	    name <hostid>localhost</hostid>, which will have the IP
	    address <hostid role="ipaddr">127.0.0.1</hostid>.</para>

	  <para>The <hostid role="domainname">FreeBSD.org</hostid>
	    domain contains a number of different hosts, including
	    <hostid role="fqdn">freefall.FreeBSD.org</hostid> and
	    <hostid role="fqdn">bento.FreeBSD.org</hostid>.</para>

	  <para>When adding an IP alias to an interface (using
	    <command>ifconfig</command>) <emphasis>always</emphasis>
	    use a netmask of
	    <hostid role="netmask">255.255.255.255</hostid>
	    (which can also be expressed as <hostid
	      role="netmask">0xffffffff</hostid>).</para>

	  <para>The MAC address uniquely identifies every network card
	    in existence.  A typical MAC address looks like <hostid
	      role="mac">08:00:20:87:ef:d0</hostid>.</para>
	</example>
      </sect3>

      <sect3>
	<title>Usernames</title>

	<note>
	  <title>&os; Extension</title>

	  <para>These elements are part of the FreeBSD extension to
	    DocBook, and do not exist in the original DocBook
	    DTD.</para>
	</note>

	<para>When you need to refer to a specific username, such as
	  <literal>root</literal> or <literal>bin</literal>, use
	  <sgmltag>username</sgmltag>.</para>

	<example>
	  <title><sgmltag>username</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>To carry out most system administration functions you
  will need to be <username>root</username>.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>To carry out most system administration functions you
	    will need to be <username>root</username>.</para>
	</example>
      </sect3>

      <sect3>
	<title>Describing <filename>Makefile</filename>s</title>

	<note>
	  <title>&os; Extension</title>

	  <para>These elements are part of the FreeBSD extension to
	    DocBook, and do not exist in the original DocBook
	    DTD.</para>
	</note>

	<para>Two elements exist to describe parts of
	  <filename>Makefile</filename>s,
	  <sgmltag>maketarget</sgmltag> and
	  <sgmltag>makevar</sgmltag>.</para>

	<para><sgmltag>maketarget</sgmltag> identifies a build target
	  exported by a <filename>Makefile</filename> that can be
	  given as a parameter to <command>make</command>.
	  <sgmltag>makevar</sgmltag> identifies a variable that can be
	  set (in the environment, on the <command>make</command>
	  command line, or within the <filename>Makefile</filename>)
	  to influence the process.</para>

	<example>
	  <title><sgmltag>maketarget</sgmltag> and
	    <sgmltag>makevar</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>Two common targets in a <filename>Makefile</filename>
  are <maketarget>all</maketarget> and <maketarget>clean</maketarget>.</para>

<para>Typically, invoking <maketarget>all</maketarget> will rebuild the
  application, and invoking <maketarget>clean</maketarget> will remove
  the temporary files (<filename>.o</filename> for example) created by
  the build process.</para>

<para><maketarget>clean</maketarget> may be controlled by a number of
  variables, including <makevar>CLOBBER</makevar> and
  <makevar>RECURSE</makevar>.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>Two common targets in a <filename>Makefile</filename>
	    are <maketarget>all</maketarget> and
	    <maketarget>clean</maketarget>.</para>

	  <para>Typically, invoking <maketarget>all</maketarget> will
	    rebuild the application, and invoking
	    <maketarget>clean</maketarget> will remove the temporary
	    files (<filename>.o</filename> for example) created by the
	    build process.</para>

	  <para><maketarget>clean</maketarget> may be controlled by a
	    number of variables, including <makevar>CLOBBER</makevar>
	    and <makevar>RECURSE</makevar>.</para>
	</example>
      </sect3>

      <sect3>
	<title>Literal Text</title>

	<para>You will often need to include <quote>literal</quote>
	  text in the documentation.  This is text that is excerpted
	  from another file, or which should be copied from the
	  documentation into another file verbatim.</para>

	<para>Some of the time, <sgmltag>programlisting</sgmltag> will
	  be sufficient to denote this text.
	  <sgmltag>programlisting</sgmltag> is not always appropriate,
	  particularly when you want to include a portion of a file
	  <quote>in-line</quote> with the rest of the
	  paragraph.</para>

	<para>On these occasions, use
	  <sgmltag>literal</sgmltag>.</para>

	<example>
	  <title><sgmltag>literal</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>The <literal>maxusers 10</literal> line in the kernel
  configuration file determines the size of many system tables, and is
  a rough guide to how many simultaneous logins the system will
  support.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>The <literal>maxusers 10</literal> line in the kernel
	    configuration file determines the size of many system
	    tables, and is a rough guide to how many simultaneous
	    logins the system will support.</para>
	</example>
      </sect3>

      <sect3>
	<title>Showing Items That the User <emphasis>Must</emphasis>
	  Fill In</title>

	<para>There will often be times when you want to show the user
	  what to do, or refer to a file, or command line, or similar,
	  where the user cannot simply copy the examples that you
	  provide, but must instead include some information
	  themselves.</para>

	<para><sgmltag>replaceable</sgmltag> is designed for this
	  eventuality.  Use it <emphasis>inside</emphasis> other
	  elements to indicate parts of that element's content that
	  the user must replace.</para>

	<example>
	  <title><sgmltag>replaceable</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>]]></programlisting>

	  <para>Appearance:</para>

	  <informalexample>
	    <screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>
	  </informalexample>

	  <para><sgmltag>replaceable</sgmltag> can be used in many
	    different elements, including <sgmltag>literal</sgmltag>.
	    This example also shows that
	    <sgmltag>replaceable</sgmltag> should only be wrapped
	    around the content that the user <emphasis>is</emphasis>
	    meant to provide.  The other content should be left
	    alone.</para>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>The <literal>maxusers <replaceable>n</replaceable></literal>
  line in the kernel configuration file determines the size of many system
  tables, and is a rough guide to how many simultaneous logins the system will
  support.</para>

<para>For a desktop workstation, <literal>32</literal> is a good value
  for <replaceable>n</replaceable>.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>The
	    <literal>maxusers <replaceable>n</replaceable></literal>
	    line in the kernel configuration file determines the size
	    of many system tables, and is a rough guide to how many
	    simultaneous logins the system will support.</para>

	  <para>For a desktop workstation, <literal>32</literal> is a
	    good value for <replaceable>n</replaceable>.</para>
	</example>
      </sect3>

      <sect3>
	<title>Quoting System Errors</title>

	<para>You might want to show errors generated by FreeBSD.
	  Mark these with <sgmltag>errorname</sgmltag>.  This
	  indicates the exact error that appears.</para>

	<example>
	  <title><sgmltag>errorname</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[
<screen><errorname>Panic: cannot mount root</errorname></screen> ]]>
</programlisting>


	  <para>Appearance:</para>

	  <informalexample>
	    <screen><errorname>Panic: cannot mount root</errorname></screen>
	  </informalexample>
	</example>
      </sect3>
    </sect2>

    <sect2>
      <title>Images</title>

      <important>
	<para>Image support in the documentation is currently
	  extremely experimental.  The mechanisms described here are
	  unlikely to change, but that is not guaranteed.</para>

	<para>You will also need to install the
	  <filename role="package">graphics/ImageMagick</filename>
	  port, which is used to convert between the different image
	  formats.  This is a big port, and most of it is not
	  required.  However, while we are working on the
	  <filename>Makefile</filename>s and other infrastructure it
	  makes things easier.  This port is <emphasis>not</emphasis>
	  in the <filename role="package">textproc/docproj</filename>
	  meta port, you must install it by hand.</para>

	<para>The best example of what follows in practice is the
	  <filename>doc/en_US.ISO8859-1/articles/vm-design/</filename>
	  document.  If you are unsure of the description that
	  follows, take a look at the files in that directory to see
	  how everything hangs together.  Experiment with creating
	  different formatted versions of the document to see how the
	  image markup appears in the formatted output.</para>
      </important>

      <sect3>
	<title>Image Formats</title>

	<para>We currently support two formats for images.  The format
	  you should use will depend on the nature of your
	  image.</para>

	<para>For images that are primarily vector based, such as
	  network diagrams, time lines, and similar, use Encapsulated
	  Postscript, and make sure that your images have the
	  <filename>.eps</filename> extension.</para>

	<para>For bitmaps, such as screen captures, use the Portable
	  Network Graphic format, and make sure that your images have
	  the <filename>.png</filename> extension.</para>

	<para>These are the <emphasis>only</emphasis> formats in which
	  images should be committed to the Subversion
	  repository.</para>

	<para>Use the right format for the right image.  It is to be
	  expected that your documentation will have a mix of EPS and
	  PNG images.  The <filename>Makefile</filename>s ensure that
	  the correct format image is chosen depending on the output
	  format that you use for your documentation.  <emphasis>Do
	  not commit the same image to the repository in two different
	    formats</emphasis>.</para>

	<important>
	  <para>It is anticipated that the Documentation Project will
	    switch to using the Scalable Vector Graphic (SVG) format
	    for vector images.  However, the current state of SVG
	    capable editing tools makes this impractical.</para>
	</important>
      </sect3>

      <sect3>
	<title>Markup</title>

	<para>The markup for an image is relatively simple.  First,
	  markup a <sgmltag>mediaobject</sgmltag>.  The
	  <sgmltag>mediaobject</sgmltag> can contain other, more
	  specific objects.  We are concerned with two, the
	  <sgmltag>imageobject</sgmltag> and the
	  <sgmltag>textobject</sgmltag>.</para>

	<para>You should include one <sgmltag>imageobject</sgmltag>,
	  and two <sgmltag>textobject</sgmltag> elements.  The
	  <sgmltag>imageobject</sgmltag> will point to the name of the
	  image file that will be used (without the extension).  The
	  <sgmltag>textobject</sgmltag> elements contain information
	  that will be presented to the user as well as, or instead
	  of, the image.</para>

	<para>There are two circumstances where this can
	  happen.</para>

	<itemizedlist>
	  <listitem>
	    <para>When the reader is viewing the documentation in
	      HTML.  In this case, each image will need to have
	      associated alternate text to show the user, typically
	      whilst the image is loading, or if they hover the mouse
	      pointer over the image.</para>
	  </listitem>

	  <listitem>
	    <para>When the reader is viewing the documentation in
	      plain text.  In this case, each image should have an
	      ASCII art equivalent to show the user.</para>
	  </listitem>
	</itemizedlist>

	<para>An example will probably make things easier to
	  understand.  Suppose you have an image, called
	  <filename>fig1.png</filename>, that you want to include in the
	  document.  This image is of a rectangle with an A inside it.
	  The markup for this would be as follows.</para>

	<programlisting>&lt;mediaobject>
  &lt;imageobject>
    &lt;imagedata fileref="fig1"> <co id="co-image-ext"/>
  &lt;/imageobject>

  &lt;textobject>
    &lt;literallayout class="monospaced">+---------------+ <co id="co-image-literal"/>
|       A       |
+---------------+&lt;/literallayout>
  &lt;/textobject>

  &lt;textobject>
    &lt;phrase>A picture&lt;/phrase> <co id="co-image-phrase"/>
  &lt;/textobject>
&lt;/mediaobject></programlisting>

	<calloutlist>
	  <callout arearefs="co-image-ext">
	    <para>Include an <sgmltag>imagedata</sgmltag> element
	      inside the <sgmltag>imageobject</sgmltag> element.  The
	      <literal>fileref</literal> attribute should contain the
	      filename of the image to include, without the extension.
	      The stylesheets will work out which extension should be
	      added to the filename automatically.</para>
	  </callout>

	  <callout arearefs="co-image-literal">

	    <para>The first <sgmltag>textobject</sgmltag> should
	      contain a <sgmltag>literallayout</sgmltag> element,
	      where the <literal>class</literal> attribute is set to
	      <literal>monospaced</literal>.  This is your opportunity
	      to demonstrate your ASCII art skills.  This content will
	      be used if the document is converted to plain
	      text.</para>

	    <para>Notice how the first and last lines of the content
	      of the <sgmltag>literallayout</sgmltag> element butt up
	      next to the element's tags.  This ensures no extraneous
	      white space is included.</para>
	  </callout>

	  <callout arearefs="co-image-phrase">
	    <para>The second <sgmltag>textobject</sgmltag> should
	      contain a single <sgmltag>phrase</sgmltag> element.  The
	      contents of this will become the <literal>alt</literal>
	      attribute for the image when this document is converted
	      to HTML.</para>
	  </callout>
	</calloutlist>
      </sect3>

      <sect3>
	<title><filename>Makefile</filename> Entries</title>

	<para>Your images must be listed in the
	  <filename>Makefile</filename> in the
	  <makevar>IMAGES</makevar> variable.  This variable should
	  contain the name of all your <emphasis>source</emphasis>
	  images.  For example, if you have created three figures,
	  <filename>fig1.eps</filename>,
	  <filename>fig2.png</filename>,
	  <filename>fig3.png</filename>, then your
	  <filename>Makefile</filename> should have lines like this in
	  it.</para>

	<programlisting>&hellip;
IMAGES= fig1.eps fig2.png fig3.png
&hellip;</programlisting>

	<para>or</para>

	<programlisting>&hellip;
IMAGES=  fig1.eps
IMAGES+= fig2.png
IMAGES+= fig3.png
&hellip;</programlisting>

	<para>Again, the <filename>Makefile</filename> will work out
	  the complete list of images it needs to build your source
	  document, you only need to list the image files
	  <emphasis>you</emphasis> provided.</para>
      </sect3>

      <sect3>
	<title>Images and Chapters in Subdirectories</title>

	<para>You must be careful when you separate your documentation
	  into smaller files (see
	  <xref linkend="xml-primer-include-using-gen-entities"/>) in
	  different directories.</para>

	<para>Suppose you have a book with three chapters, and the
	  chapters are stored in their own directories, called
	  <filename>chapter1/chapter.xml</filename>,
	  <filename>chapter2/chapter.xml</filename>, and
	  <filename>chapter3/chapter.xml</filename>.  If each chapter
	  has images associated with it, it is suggested to place
	  those images in each chapter's subdirectory
	  (<filename>chapter1/</filename>,
	  <filename>chapter2/</filename>, and
	  <filename>chapter3/</filename>).</para>

	<para>However, if you do this you must include the directory
	  names in the <makevar>IMAGES</makevar> variable in the
	  <filename>Makefile</filename>, <emphasis>and</emphasis> you
	  must include the directory name in the
	  <sgmltag>imagedata</sgmltag> element in your
	  document.</para>

	<para>For example, if you have
	  <filename>chapter1/fig1.png</filename>, then
	  <filename>chapter1/chapter.xml</filename> should
	  contain:</para>

	<programlisting>&lt;mediaobject>
  &lt;imageobject>
    &lt;imagedata fileref="chapter1/fig1"> <co id="co-image-dir"/>
  &lt;/imageobject>

  &hellip;

&lt;/mediaobject></programlisting>

	<calloutlist>
	  <callout arearefs="co-image-dir">
	    <para>The directory name must be included in the
	      <literal>fileref</literal> attribute.</para>
	  </callout>
	</calloutlist>

	<para>The <filename>Makefile</filename> must contain:</para>

	<programlisting>&hellip;
IMAGES=  chapter1/fig1.png
&hellip;</programlisting>

	<para>Then everything should just work.</para>
      </sect3>
    </sect2>

    <sect2>
      <title>Links</title>

      <note>
	<para>Links are also in-line elements.</para>
      </note>

      <sect3>
	<title>Linking to Other Parts of the Same Document</title>

	<para>Linking within the same document requires you to specify
	  where you are linking from (i.e., the text the user will
	  click, or otherwise indicate, as the source of the link) and
	  where you are linking to (the link's destination).</para>

	<para>Each element within DocBook has an attribute called
	  <literal>id</literal>.  You can place text in this attribute
	  to uniquely name the element it is attached to.</para>

	<para>This value will be used when you specify the link
	  source.</para>

	<para>Normally, you will only be linking to chapters or
	  sections, so you would add the <literal>id</literal>
	  attribute to these elements.</para>

	<example>
	  <title>Attribute <literal>id</literal> on Chapters and
	    Sections</title>

	  <programlisting><![CDATA[<chapter id="chapter1">
  <title>Introduction</title>

  <para>This is the introduction.  It contains a subsection,
    which is identified as well.</para>

  <sect1 id="chapter1-sect1">
    <title>Sub-sect 1</title>

    <para>This is the subsection.</para>
  </sect1>
</chapter>]]></programlisting>
	</example>

	<para>Obviously, you should use more descriptive values.  The
	  values must be unique within the document (i.e., not just
	  the file, but the document the file might be included in as
	  well).  Notice how the <literal>id</literal> for the
	  subsection is constructed by appending text to the
	  <literal>id</literal> of the chapter.  This helps to ensure
	  that they are unique.</para>

	<para>If you want to allow the user to jump into a specific
	  portion of the document (possibly in the middle of a
	  paragraph or an example), use <sgmltag>anchor</sgmltag>.
	  This element has no content, but takes an
	  <literal>id</literal> attribute.</para>

	<example>
	  <title><sgmltag>anchor</sgmltag></title>

	  <programlisting><![CDATA[<para>This paragraph has an embedded
  <anchor id="para1">link target in it.  It will not show up in
  the document.</para>]]></programlisting>
	</example>

	<para>When you want to provide the user with a link they can
	  activate (probably by clicking) to go to a section of the
	  document that has an <literal>id</literal> attribute, you
	  can use either <sgmltag>xref</sgmltag> or
	  <sgmltag>link</sgmltag>.</para>

	<para>Both of these elements have a <literal>linkend</literal>
	  attribute.  The value of this attribute should be the value
	  that you have used in a <literal>id</literal> attribute (it
	  does not matter if that value has not yet occurred in your
	  document; this will work for forward links as well as
	  backward links).</para>

	<para>If you use <sgmltag>xref</sgmltag> then you have no
	  control over the text of the link.  It will be generated for
	  you.</para>

	<example>
	  <title>Using <sgmltag>xref</sgmltag></title>

	  <para>Assume that this fragment appears somewhere in a
	    document that includes the <literal>id</literal>
	    example:</para>

	  <programlisting><![CDATA[<para>More information can be found
  in <xref linkend="chapter1"/>.</para>

<para>More specific information can be found
  in <xref linkend="chapter1-sect1"/>.</para>]]></programlisting>

	  <para>The text of the link will be generated automatically,
	    and will look like (<emphasis>emphasized</emphasis> text
	    indicates the text that will be the link):</para>

	  <blockquote>
	    <para>More information can be found in <emphasis>Chapter
		One</emphasis>.</para>

	    <para>More specific information can be found in
	      <emphasis>the section called Sub-Sect
		1</emphasis>.</para>
	  </blockquote>
	</example>

	<para>Notice how the text from the link is derived from the
	  section title or the chapter number.</para>

	<note>
	  <para>This means that you <emphasis>cannot</emphasis> use
	    <sgmltag>xref</sgmltag> to link to an
	    <literal>id</literal> attribute on an
	    <sgmltag>anchor</sgmltag> element.  The
	    <sgmltag>anchor</sgmltag> has no content, so the
	    <sgmltag>xref</sgmltag> cannot generate the text for the
	    link.</para>
	</note>

	<para>If you want to control the text of the link then use
	  <sgmltag>link</sgmltag>.  This element wraps content, and
	  the content will be used for the link.</para>

	<example>
	  <title>Using <sgmltag>link</sgmltag></title>

	  <para>Assume that this fragment appears somewhere in a
	    document that includes the <literal>id</literal>
	    example.</para>

	  <programlisting><![CDATA[<para>More information can be found in
  <link linkend="chapter1">the first chapter</link>.</para>

<para>More specific information can be found in
  <link linkend="chapter1-sect1">this</link> section.</para>]]></programlisting>

	  <para>This will generate the following
	    (<emphasis>emphasized</emphasis> text indicates the text
	    that will be the link):</para>

	  <blockquote>
	    <para>More information can be found in <emphasis>the first
		chapter</emphasis>.</para>

	    <para>More specific information can be found in
	      <emphasis>this</emphasis> section.</para>
	  </blockquote>
	</example>

	<note>
	  <para>That last one is a bad example.  Never use words like
	    <quote>this</quote> or <quote>here</quote> as the source
	    for the link.  The reader will need to hunt around the
	    surrounding context to see where the link is actually
	    taking them.</para>
	</note>

	<note>
	  <para>You <emphasis>can</emphasis> use
	    <sgmltag>link</sgmltag> to include a link to an
	    <literal>id</literal> on an <sgmltag>anchor</sgmltag>
	    element, since the <sgmltag>link</sgmltag> content defines
	    the text that will be used for the link.</para>
	</note>
      </sect3>

      <sect3>
	<title>Linking to Documents on the WWW</title>

	<para>Linking to external documents is much simpler, as long
	  as you know the URL of the document you want to link to.
	  Use <sgmltag>ulink</sgmltag>.  The <literal>url</literal>
	  attribute is the URL of the page that the link points to,
	  and the content of the element is the text that will be
	  displayed for the user to activate.</para>

	<example>
	  <title><sgmltag>ulink</sgmltag></title>

	  <para>Use:</para>

	  <programlisting><![CDATA[<para>Of course, you could stop reading this document and
  go to the <ulink url="&url.base;/index.html">FreeBSD
  home page</ulink> instead.</para>]]></programlisting>

	  <para>Appearance:</para>

	  <para>Of course, you could stop reading this document and go
	    to the <ulink url="&url.base;/index.html">FreeBSD home
	      page</ulink> instead.</para>
	</example>
      </sect3>
    </sect2>
  </sect1>
</chapter>