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<!-- Copyright (c) 1998, 1999 Nik Clayton, All rights reserved.

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     $FreeBSD: doc/en_US.ISO_8859-1/books/fdp-primer/sgml-markup/chapter.sgml,v 1.18 2001/01/03 11:12:41 nik Exp $
-->

<chapter id="sgml-markup">
  <title>SGML Markup</title>

  <para>This chapter describes the three 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 FreeBSD Documentation Project mailing list
    <email>freebsd-doc@FreeBSD.org</email>.</para>

  <note>
    <title>Inline vs. 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>
    <title>HTML</title>
    
    <para>HTML, the HyperText Markup Language, is the markup language of
      choice on the World Wide Web.  More information can be found at
      &lt;URL:<ulink
	url="http://www.w3.org/">http://www.w3.org/</ulink>&gt;.</para>

    <para>HTML is used to markup pages on the FreeBSD web site.  It should not
      (generally) be used to mark up other documention, since DocBook offers a
      far richer set of elements to choose from.  Consequently, you will
      normally only encounter HTML 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, and the
      latest, 4.0 (available in both <emphasis>strict</emphasis> and
      <emphasis>loose</emphasis> variants).</para>
	  
    <para>The HTML DTDs are available from the ports collection in the
      <filename>textproc/html</filename> port.  They are automatically
      installed as part of the <filename>textproc/docproj</filename>
      port.</para>

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

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

      <para>The majority of HTML documents on the FreeBSD web site comply with
	the loose version of HTML 4.0.</para>

      <programlisting>PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"</programlisting>
    </sect2>

    <sect2>
      <title>Sectional elements</title>

      <para>An HTML document is normally split in to 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 HTML document structure</title>

	<programlisting>&lt;html>
  &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>HTML 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>, etc.</title>

	  <para>Use:</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 HTML 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, preceeding 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><![ CDATA [<h1>First section</h1>

<!-- Document introduction -->

<h3>Sub-section</h3>

<!-- This is bad, <h2> has been left out -->]]></programlisting>
	</example>
      </sect3>
      
      <sect3>
	<title>Paragraphs</title>

	<para>HTML 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
  preceeded 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></dd>

    <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>Paragraph 1 of definition 3.  Note that the &lt;p&gt;
    element is not required in the single paragraph case.</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 in to 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 e-mail
	    message;</para>

	  <programlisting><![ CDATA [<pre>  From: nik@FreeBSD.org
  To: freebsd-doc@FreeBSD.org
  Subject: New documentation available

  There's a new copy of my primer for contributers to the FreeBSD
  Documentation Project available at

    <URL:http://people.FreeBSD.org/~nik/primer/index.html>

  Comments appreciated.

  N</pre>]]></programlisting>
	</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 of 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 in to 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 in to
         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>
      </sect3>
    </sect2>

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

      <sect3>
	<title>Emphasising information</title>

	<para>You have two levels of emphasis available in HTML,
	  <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.</para>

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

	  <para>Use:</para>

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

      <sect3>
	<title>Bold and italics</title>

	<para>Because HTML includes presentational markup, you can also
	  indicate that particular content should be rendered in bold or
	  italic.  The elements are <sgmltag>b</sgmltag> and
	  <sgmltag>i</sgmltag> respectively.</para>

	<example>
	  <title><sgmltag>b</sgmltag> and <sgmltag>i</sgmltag></title>

	  <programlisting><![ CDATA [<p><b>This</b> is in bold, while <i>this</i> is
  in italics.</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
	  &ldquo;teletype&rdquo;).</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 e-mail as
  <tt>nik@FreeBSD.org</tt>.</p>]]></programlisting>
	</example>
      </sect3>

      <sect3>
	<title>Content size</title>

	<para>You can indicate that content should be shown in a larger or
	  smaller font.  There are three ways of doing this.</para>

	<orderedlist>
	  <listitem>
	    <para>Use <sgmltag>big</sgmltag> and <sgmltag>small</sgmltag>
	      around the content you wish to change size.  These tags can be
	      nested, so <literal>&lt;big&gt;&lt;big&gt;This is much
		bigger&lt;/big&gt;&lt;/big&gt;</literal> is possible.</para>
	  </listitem>

	  <listitem>
	    <para>Use <sgmltag>font</sgmltag> with the <literal>size</literal>
	      attribute set to <literal>+1</literal> or <literal>-1</literal>
	      respectively.  This has the same effect as using
	      <sgmltag>big</sgmltag> or <sgmltag>small</sgmltag>.  However,
	      the use of this approach is deprecated.</para>
	  </listitem>

	  <listitem>
	    <para>Use <sgmltag>font</sgmltag> with the <literal>size</literal>
	    attribute set to a number between 1 and 7.  The default font size
	      is <literal>3</literal>.  This approach is deprecated.</para>
	  </listitem>
	</orderedlist>

	<example>
	  <title><sgmltag>big</sgmltag>, <sgmltag>small</sgmltag>, and
	    <sgmltag>font</sgmltag></title>

	  <para>The following fragments all do the same thing.</para>

	  <programlisting><![ CDATA [<p>This text is <small>slightly smaller</small>.  But
  this text is <big>slightly bigger</big>.</p>

<p>This text is <font size="-1">slightly smaller</font>.  But
  this text is <font size="+1">slightly bigger</font.</p>

<p>This text is <font size="2">slightly smaller</font>.  But
  this text is <font size="4">slightly bigger</font>.</p>]]></programlisting>
	</example>
      </sect3>
    </sect2>

    <sect2>
      <title>Links</title>

      <note>
	<para>Links are also in-line 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
	  colour, 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>name</literal> attribute instead of
	  <literal>href</literal>.</para>

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

	  <para>Use:</para>

	  <programlisting><![ CDATA [<p><a name="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 name 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 preceeding <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>
    <title>DocBook</title>

    <para>DocBook was designed by the <ulink
	url="http://www.oreilly.com/davenport/">Davenport Group</ulink> to be
      a DTD for writing technical documentation.  As such, and unlike LinuxDoc
      and HTML, 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><literal>formal</literal> vs. <literal>informal</literal></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 information
	version of the element.  The informal version will not have a
	title.</para>
    </note>
    
    <para>The DocBook DTD is available from the ports collection in the
      <filename>textproc/docbook</filename> port.  It is automatically
      installed as part of the <filename>textproc/docproj</filename>
      port.</para>
    
    <sect2>
      <title>FreeBSD 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
	&ldquo;DocBook&rdquo; 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 Nik Clayton <email>nik@FreeBSD.org</email>.</para>
      </note>

      <para>The FreeBSD extensions are not (currently) in the ports
	collection.  They are stored in the FreeBSD CVS tree, as <ulink
	url="http://www.freebsd.org/cgi/cvsweb.cgi/doc/share/sgml/freebsd.dtd">doc/share/sgml/freebsd.dtd</ulink>.</para>
    </sect2>

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

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

	<programlisting>PUBLIC "-//FreeBSD//DTD DocBook V4.1-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 organised 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 organisation.
	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 organised 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="http://www.FreeBSD.org/tutorials/">FreeBSD
	  tutorials</ulink> are all marked up as articles, while this
	document, the <ulink url="http://www.FreeBSD.org/FAQ/">FreeBSD
	  FAQ</ulink>, and the <ulink
	  url="http://www.FreeBSD.org/handbook/">FreeBSD Handbook</ulink> are
	all marked up as books.</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 e-mail 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 e-mail address</replaceable>"><replaceable>Your name</replaceable>&lt;/holder>
    &lt;/copyright>

    &lt;pubdate role="rcs">&#36;Date&#36;&lt;/pubdate>

    &lt;releaseinfo>&#36;Id&#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>artheader</sgmltag>.</para>

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

	  <!-- Can't put this in a marked section because of the
               replaceable elements -->
	  <programlisting>&lt;article>
  &lt;artheader>
    &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 e-mail 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 e-mail address</replaceable>"><replaceable>Your name</replaceable>&lt;/holder>
    &lt;/copyright>

    &lt;pubdate role="rcs">&#36;Date&#36;&lt;/pubdate>

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

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

  &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><![ RCDATA [<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 the 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>s</title>

	<para>You can introduce another layer of organisation 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>
	  
	  <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 &ldquo;meta&rdquo;
	  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
    harddisk.</para>
</warning>]]></programlisting>
	  </example>
	  
	<!-- Need to do this outside of the example -->
	<warning>
	  <para>Installing FreeBSD may make you want to delete Windows from
	    your harddisk.</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're 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 analagous 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>
  <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>
	    <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>If you don't 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">
	    <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 in to 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 OS, 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>Emphasising information</title>
	
	<para>When you want to emphasise 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>Applications, commands, options, and cites</title>
	
	<para>You will frequently want to refer to both applications and
	  commands when writing for the Handbook.  The distinction between
	  them is simple: an application is the name for a suite (or possibly
	  just 1) of programs that fulfil 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 &ldquo;command(number)&rdquo; 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="sgml-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/sgml/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 &ldquo;in-line&rdquo; but present it as something the
	  user should type in.</para>

	<para>Use <sgmltag>option</sgmltag> to mark up a command's
	  options.</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.8;, and &man.newaliases.8;
  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>, <citerefentry>
	      <refentrytitle>mailq</refentrytitle>
	      <manvolnum>8</manvolnum>
	    </citerefentry>, and <citerefentry>
	      <refentrytitle>newaliases</refentrytitle>
	      <manvolnum>8</manvolnum>
	    </citerefentry> 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>/usr/doc/en/handbook/</filename>.  The first
  file is called <filename>handbook.sgml</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.sgml</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>Devices</title>
	
	<note>
	  <title>FreeBSD 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>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>FreeBSD 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 role attribute, or
	      <literal>role="hostname"</literal></term>
	    
	    <listitem>
	      <para>With no role 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 seperated 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">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
  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>FreeBSD 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>FreeBSD 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 &ldquo;literal&rdquo; text in the
	  Handbook.  This is text that is excerpted from another file, or
	  which should be copied from the Handbook 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 &ldquo;in-line&rdquo; 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
	  can not 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 [<informalexample>
  <screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>
</informalexample>]]></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>
    </sect2>

    <sect2>
      <title>Images</title>

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

	<para>You will also need to install the
	  <filename>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're working on the
	  <filename>Makefile</filename>s and other infrastructure it makes
	  things easier.  This port is <emphasis>not</emphasis> in the
	  <filename>textproc/docproj</filename> meta port, you must install it
	  by hand.</para>

	<para>The best example of what follows in practice is the
	  <filename>en_US.ISO_8859-1/articles/vm-design/</filename> document.
	  If you're unsure of the description that follows, take a look at the
	  files in that directory to see how everything hangs togther.
	  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, timelines, 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 CVS 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</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 in to
	  smaller files (see <xref linkend="sgml-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.sgml</filename>,
	  <filename>chapter2/chapter.sgml</filename>, and
	  <filename>chapter3/chapter.sgml</filename>.  If each chapter has
	  images associated with it, I suggest you 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.sgml</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 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><literal>id on chapters and sections</literal></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 won't 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>emphasised</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>can not</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> can not 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>emphasised</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
	    &ldquo;this&rdquo; or &ldquo;here&rdquo; 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="http://www.FreeBSD.org/">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="http://www.FreeBSD.org/">FreeBSD home page</ulink>
	    instead.</para>
	</example>
      </sect3>
    </sect2>
  </sect1>
  
  <sect1>
    <title>* LinuxDoc</title>
    
    <para>LinuxDoc is an adaptation of the QWERTZ DTD, first adopted by the
      <ulink url="http://www.linuxdoc.org/">Linux Documentation
	Project</ulink>, and subsequently adopted by the FreeBSD Documentation
      Project.</para>
    
    <para>The LinuxDoc DTD contains primarily appearance related markup rather
      than content related markup (i.e., it describes what something looks
      like rather than what it is).</para>
    
    <para>Both the FreeBSD Documentation Project and the Linux Documentation
      Project are migrating from the LinuxDoc DTD to the DocBook DTD.</para>
    
    <para>The LinuxDoc DTD is available from the ports collection in the
      <filename>textproc/linuxdoc</filename> category.</para>
  </sect1>
</chapter>


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