Installer needs option to conditionally install files. In some installs, like a new install, the installer should install a file but that same file should not be overwriten on an update. For example, a database file that is updated by the user will be overwriten by the installer. The options required are:
Install file if not present.
Install file or not install if file is modified.
InstallShield should be consulted for the various options required.