<chapter id="help-0">
  <title>Help System</title>
  <highlights>
    <para>This chapter describes the Help system in the GNOME Desktop.</para>
  </highlights>
  <sect1 id="help-1">
    <title>Introduction to the Help System</title>
    <indexterm>
      <primary>online Help</primary>
      <see>Help</see>
    </indexterm>
    <indexterm>
      <primary>Help</primary>
      <secondary>introduction</secondary>
    </indexterm>
    <para>The GNOME Desktop displays help in the <application>Yelp</application> Help
browser. For more information, see <ulink url="ghelp:user-guide?yelp">Yelp Help Browser</ulink> in the
<ulink url="ghelp:user-guide">GNOME Desktop User Guide</ulink>.</para>
<para>The source documents for the help are XML files. The XML files are
written to the DocBook XML Version 4.1.2 document type definition (DTD). The
DocBook XML files are converted to HTML using stylesheets installed with <application>
gnome-doc-utils</application> and the HTML is displayed in the
help browser. For more information on DocBook XML, see the following URL:</para>
    <literallayout>
      <ulink url="http://www.oasis-open.org/docbook/xml/">http://www.oasis-open.org/docbook/xml</ulink>
    </literallayout>
    <para>The Help system uses <firstterm>Open Source Metadata Framework</firstterm>
(OMF) files, and a cataloging system. The next sections describe OMF files
and the cataloging system.</para>
  </sect1>
  <sect1 id="help-3">
    <title>OMF Files</title>
    <indexterm>
      <primary>.omf files</primary>
      <see>OMF files</see>
    </indexterm>
    <indexterm>
      <primary>Help</primary>
      <secondary>OMF files</secondary>
    </indexterm>
    <indexterm>
      <primary>OMF files</primary>
    </indexterm>
    <para>The XML file for each manual
has an associated OMF file. The OMF file contains information about the manual
that is used by the Help browser. OMF files have a <filename>.omf</filename>
extension.</para>
    <para>When you install an application, the installation process installs an
OMF file to a directory of OMF files. If a Help document has an associated
OMF file in an OMF file directory, the Help document is displayed in the Help
browser.</para>
    <para>OMF files contain information about Help documents such as the following:</para>
    <itemizedlist>
      <listitem>
        <para>The location of the XML file for the Help document</para>
      </listitem>
      <listitem>
        <para>The title of the Help document</para>
      </listitem>
      <listitem>
        <para>A subject category to which the Help document belongs</para>
      </listitem>
    </itemizedlist>
    <para>For more information on how to create OMF files, please see 
    <ulink url="ghelp:writing_scrollkeeper_omf_files">Writing Scrollkeeper 
OMF Files</ulink>.</para>
  </sect1>
  <sect1 id="help-2">
    <title>ScrollKeeper Cataloging System</title>
    <indexterm>
      <primary>Help</primary>
      <secondary>ScrollKeeper cataloging system</secondary>
    </indexterm>
    <indexterm>
      <primary>ScrollKeeper cataloging system</primary>
    </indexterm>
    <para><application>ScrollKeeper</application> is a cataloging
system for documentation.  Its primary function is to manage the information in 
OMF files for the help browser.  When you install an application, the 
OMF file is copied to the <filename>
<replaceable>$prefix</replaceable>/share/omf/<replaceable>&lt;application-name&gt;</replaceable>
</filename> directory.
</para>

    <para><application>ScrollKeeper</application> builds a table of contents from the
collection of OMF files in the directories specified in 
<filename><replaceable>$prefix</replaceable>/etc/scrollkeeper.conf</filename> file. 
This file usually consists of a single line with the <varname>OMF_DIR</varname> 
set to a comma separated list of directories to recursively search.</para>

    <programlisting>OMF_DIR=/usr/share/omf:/usr/local/share/omf:/opt/gnome2/share/omf:/opt/kde/omf
</programlisting>

    <para><application>ScrollKeeper</application> contains a hierarchy of subject
categories to which a help document can belong. The subject category of the document 
in the OMF file determines the location of the document in the table of contents presented
by the help browser.</para>

    <para>The hierarchy of subject categories is defined in the file
<filename>
<replaceable>$prefix</replaceable>/scrollkeeper/Templates/<replaceable>&lt;lang&gt;</replaceable>/scrollkeeper_cl.xml</filename>. 
The subject category of a document must correspond to a category specified in this file.</para>

    <para>For more information on the <application>Scrollkeeper</application> system,
visit the website at 
<ulink url="http://scrollkeeper.sourceforge.net/">http://scrollkeeper.sourceforge.net/</ulink>.
</para>

    <note>
      <para>If the help document XML file is moved to a new location, then
the location in the OMF file needs to be updated.</para>
    </note>
  </sect1>
</chapter>
