<contexts>
    <context id="viewer" title="Sample View">
        <description>This is the context help for the sample view with a tree viewer. It was generated by a PDE template.</description>
        <topic href="/PLUGINS_ROOT/org.eclipse.platform.doc.isv/guide/ua_help_context.htm" label="Context-sensitive help">
            <enablement>
                <with variable="platform">
                    <test property="org.eclipse.core.runtime.isBundleInstalled" args="org.eclipse.platform.doc.isv"/>
                 </with>
            </enablement>
        </topic>
    </context>
</contexts>