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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
                  "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>

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############# -->

<sect1 id="refering">
  <title>Cross Referencing Other Documentation</title>
  <para>
	In many circumstances you may want to create a link from one
	document to another.  This can be done using GNOME's virtual
	filesystem layer.  You use a specific Uniform Resource Identifier
	(URI) scheme to identify the type of documentation.  There are different 
	schemas which tell <application>Yelp</application> what type of document 
	the you are referencing. 
  </para>

<!-- ####### Cross Referencing Other Documentation | Uniform Resource
Identifier ####### -->

  <sect2 id="uri">
	<title>Uniform Resource Identifier</title>

	<para>
	  The Uniform Resource Identifier (URI) is made up of three
	  parts: the schema, the document and the id.  The schema declares
	  the type of document.  Some of the well known schemas are:
	  http://, ftp://, file://.  There are three specific schemas
	  identifying documentation in GNOME 2.  The schema ghelp:
	  identifies GNOME documentation.  The schema <literal>man:</literal> is used to
	  reference man pages and the schema info: identifies info
	  pages. <application>Yelp</application> only uses the schemas
	  ghelp:, man: and info: to cross reference documentation
	  you must use one of those three schemas.
	</para>

	<para>
	  The second part of the URI is the document.  This is really the
	  path to the document and identifying the document itself.  You
	  can either give the full path to the document on the computer,
	  give the filename of the document, or just give the appid.  It
	  is not recommended to use the full path of the document to
	  reference documentation.  This will lead to broken links and
	  heartaches.  You should always either use the name of the
	  document (e.g. gedit.xml) or use the appid to reference the main
	  documentation (e.g. gedit).
	</para>

	<note>
	  <para>
		The appid is the way the GNOME build system identifies
		applications.  The appid is unique, but sometimes it is hard
		to deduce the appid.  The appid is typically the name of the
		module in CVS.  An example is the appid for the GNOME Terminal
		is gnome-terminal and its module name in CVS is also
		gnome-terminal.  For some applications this rule of thumb does
		not hold.  An example is the appid for the Stock Ticker is
		gtik2_applet2, but its module name in CVS is gtik.  If you are
		having trouble figuring out the appid of an application ask
		the maintainer of the program.
	  </para>
	</note>

	<para>
	  The third part of the URI is the id.  The id is the unique
	  DocBook id made for every section.  For more information on
	  section ids see <xref linkend="guidelines-sectids"/>.  The id is optional, but
	  will let you choose where in the document the reader will look
	  instead of placing the reader at the table of contents.  It is
	  recommended to use ids in the URI to accurately direct the
	  reader to a specific portion of the document.
	</para>

	<para>
	  The three parts of the URI are put together to cross reference
	  documentation in GNOME.  The URI is formed by placing the schema
	  first, followed by the appid or filename of the document.  A
	  question mark is placed after the appid, but before the section
	  id.  Then the section id is put after the question mark.  The
	  complete URI looks like:
	  <programlisting>
ghelp:gedit?intro
	  </programlisting>
	  In the above example the schema is <quote>ghelp:</quote>, the
	  appid is <quote>gedit</quote>, and the section id is
	  <quote>intro</quote>. Note the absence of slashes after the schema: with slashes, what
	  follows is assumed to be a file rather than an appid.
	</para>

  </sect2>

<!-- ####### Cross Referencing Other Documentation | GNOME Documentation 
####### -->

  <sect2 id="refergnome">
	<title>GNOME Documentation</title>
	<para>
	  Adding a link to a different GNOME help document is not hard.
	  This is done using the <quote>ghelp:</quote> URI scheme.  This
	  works for documents which are shipped as XML.  To cross
	  reference another GNOME document, use:
<programlisting>
&lt;ulink type="help" url="ghelp:user-guide?gosbasic-2"&gt;text&lt;/ulink&gt;
</programlisting>
      where <quote>ghelp:</quote> is the schema,
      <quote>user-guide</quote> is the appid of the <citetitle>User's
      Guide</citetitle>, <quote>gosbasic-2</quote> is the section id,
      and <quote>text</quote> is the text which becomes the link.
    </para>
    <para>To link within the current document, you need only specify the section id you wish to link to, but the DocBook syntax is different. To create a link that displays the section number and name, use:
<programlisting>
&lt;xref linkend="intro" /&gt;
</programlisting>    
    To create a link and specify the link text, use:
<programlisting>
&lt;link linkend="intro"&gt;text&lt;/link&gt;
</programlisting>      
    </para>
    
	</sect2>

<!-- ####### Cross Referencing Other Documentation | Man and Info Pages 
####### -->

	<sect2 id="refermanpages">
	  <title>Man and Info Pages</title>

	  <para>
	  Adding a link to a manpage in a GNOME document is done using the
	  <quote>man:</quote> URI scheme.  To cross reference a manpage,
	  use:
<programlisting>
&lt;ulink type="help" url="man:foo"&gt;text&lt;/ulink&gt;
</programlisting>
	  </para>

	  <para>
	  Adding a link to an infopage in a GNOME document is done using
	  the <quote>info:</quote> URI scheme.  To cross reference a
	  manpage, use:
<programlisting>
&lt;ulink type="help" url="info:foo"&gt;text&lt;/ulink&gt;
</programlisting>
	  </para>

	</sect2>
	<sect2 id="referweb">
	  <title>Web Pages</title>
	  <para>To link to web pages, use:
<programlisting>
&lt;ulink type="http" url="http://www.gnome.org"&gt;GNOME Web Site&lt;/ulink&gt;
</programlisting>
	</para>
	</sect2>
  </sect1>
