The UpdateShield system uses two index files for checking for new updates, which include the Client Side and Server Side index files. These index files are XML files that contain the update properties. When performing software update, the Updater loads the Server Side index file from the server and checks against its Client Side index file to determine whether a new update is available.
One of the main properties in both index files include release ID, which encodes version number, release date, Key ID, and Program ID. The Updater checks for update by decoding the release ID from both the Client Side and Server Side index files. A new update is available when the version number on the Server Side index file is higher than the version number on the Client Side index file.