# Help System

This chapter describes the Help system in the GNOME Desktop.

## Introduction to the Help System

The GNOME Desktop displays Help in the Yelp Help browser. 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, and the HTML is displayed in the Help browser. For more information on DocBook XML, see the following URL:

          http://www.oasis-open.org/docbook/xml

The Help system uses Open Source Metadata Framework (OMF) files, and a cataloging system. The next sections describe OMF files and the cataloging system.

## OMF Files

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 `.omf` extension.

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.

OMF files contain information about Help documents such as the following:

- The location of the XML file for the Help document

- The title of the Help document

- A subject category to which the Help document belongs

## ScrollKeeper Cataloging System

ScrollKeeper is a cataloging system for documentation. The Help browser uses ScrollKeeper to catalog the manuals on the system. ScrollKeeper manages the information in the OMF files for the Help browser.

ScrollKeeper uses the information in the OMF files to enable the Help browser to find Help documents on a system. When you install an application, the installation process installs an OMF file to a directory of OMF files.

ScrollKeeper builds a table of contents for each Help document that has an associated OMF file. ScrollKeeper builds the table of contents from the XML file specified in the OMF file. The table of contents for the Help document is displayed in the left pane of the Help browser window, and enables users to navigate the Help document in the left pane. The title of the document in the OMF file is also displayed in the left pane of the Help browser window.

ScrollKeeper contains a hierarchy of subject categories to which a Help document can belong. The Help documents are organized into this hierarchy of subject categories in the left pane of the Help browser window. The subject category of the document in the OMF file determines the location of the document in the hierarchy. The hierarchy of subject categories is defined in the following file:

`/usr/share/scrollkeeper/Templates/C/scrollkeeper_cl.xml`

The subject category of a document must correspond to a subject category in the following file:

`/usr/share/scrollkeeper/Templates/C/scrollkeeper_cl.xml`

If the Help document XML file is moved to a new location, then you might need to update the location in the OMF file.