<?xml version="1.0" encoding="utf-8"?>
<!--
   Copyright (c) 2002 Douglas Gregor <doug.gregor -at- gmail.com>
  
   Distributed under the Boost Software License, Version 1.0.
   (See accompanying file LICENSE_1_0.txt or copy at
   http://www.boost.org/LICENSE_1_0.txt)
  -->
<!DOCTYPE chapter PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN"
  "http://www.boost.org/tools/boostbook/dtd/boostbook.dtd">
<chapter xmlns:xi="http://www.w3.org/2001/XInclude" id="boostbook.together"
         last-revision="$Date$">
  <title>Bringing Together a BoostBook Document</title>

  <section id="boostbook.linking">
    <title>Linking in BoostBook</title> 

    <para>How one links to another element in BoostBook depends
    greatly on the nature of the element linked and how the link
    should appear. There are three general linking elements:
    &lt;xref&gt;, &lt;link&gt;, and &lt;ulink&gt;. Additionally, there
    are linking elements for referencing specific types of entities,
    such as classes (&lt;classname&gt;), functions
    (&lt;functionname&gt;), or libraries (&lt;libraryname&gt;).</para>

    <para>The &lt;xref&gt; element references elements that have an
    <code>id</code> attribute and a title. The actual link text is
    composed from title and type of the element referenced. To link to
    a particular ID, create an &lt;xref&gt; element with the
    <code>linkend</code> attribute set to the ID of the intended
    target. For instance, this section's ID is
    <code>boostbook.linking</code>, so we create a reference it to
    with <code>&lt;xref linkend="boostbook.linking"/&gt;</code>, which
    will look like this in the text: <xref
    linkend="boostbook.linking"/>.</para>

    <para>The &lt;link&gt; element references an ID in the same way as
    &lt;xref&gt;, except that &lt;link&gt; does not generate any text
    for the link, so text must be supplied within the element. For
    instance, we can again link to this chapter but this time specify
    our own text with <code>&lt;link
    linkend="boostbook.linking"&gt;like this&lt;/link&gt;</code>. This
    markup will result in a link to this chapter that looks <link
    linkend="boostbook.linking">like this</link>.</para>

    <para>The &lt;ulink&gt; element references a URL that is outside
    of the DocBook document. The <code>url</code> attribute contains
    the URL to link to, and the element data provides the link
    text.For instance, we can link to the the Boost web site with
    <code>&lt;ulink
    url="http://www.boost.org"&gt;Boost&lt;/ulink&gt;,</code> which
    appears in the document like this: <ulink
    url="http://www.boost.org">Boost</ulink>.</para>
    
    <para>In BoostBook, &lt;ulink&gt; supports a custom url schema for
    linking to files within the boost distribution. This is formed by
    setting the <code>url</code> attribute to <code>boost:</code>
    followed by the file's path. For example, we can link to the
    flyweight library with
    <code>&lt;ulink
    url="boost:/libs/flyweight/index.html"&gt;Boost.Flyweight&lt;/ulink&gt;</code>,
    which will appear like this: <ulink
    url="boost:/libs/flyweight/index.html">Boost.Flyweight</ulink>.
    This schema is only supported for BoostBook &lt;ulink&gt; elements.
    It isn't available for any other elements or in Docbook.</para>

    <para>The &lt;classname&gt;, &lt;functionname&gt;,
    &lt;methodname&gt;, and &lt;libraryname&gt; link to classes,
    functions, methods, and libraries, respectively. The text of each
    element gives both the name of the element to link to and the link
    text. For instance, we can link to the Function library with
    <code>&lt;libraryname&gt;Function&lt;/libraryname&gt;</code>,
    which results in the following:
    <libraryname>Function</libraryname>. In cases where the displayed
    text is different from the actual name, the <code>alt</code>
    attribute can be specified. For instance, the following XML
    element references the <classname>boost::function</classname>
    class template but displays the text <classname
    alt="boost::function">function</classname>: <code>&lt;classname
    alt="boost::function"&gt;function&lt;/classname&gt;</code>.</para>
  </section>
</chapter>
