The global context is a central repository for custom key-value pairs that are available to both application development and configuration. You can place, retrieve, and delete global context values based on their unique keys.
To update a global context, use the updateGlobalContext action. The same syntax and parameters apply as for the local context.
<ListItem feed="MovieTitles">
  <Event eventId="onClick">
    <Action actionId="updateGlobalContext">
      <P pid="releaseYear" value="{$MovieTitles.ReleaseYear}" />
    </Action>
  </Event>
</ListItem>
Although
            tiles should use the local context, they can also access data that is available in the
            global context. To access global context elements, use the
                {$_global.<value>} syntax. This example shows how
                TileWithGlobalContext uses values that are stored in the global
            context:<Tile tileId="TileWithGlobalContext">
	<LinearContainer layout="vertical">
        	<!-- Details skipped for brevity -->
		<UIElement type="label">
			<P pid="text" value="{$_global. MovieTitles.ReleaseYear }" />
		</UIElement>
		<UIElement type="label">
			<P pid="text" value="{$_context.type}" />
		</UIElement>
	</LinearContainer>
</Tile>