For security reasons, if you provide the parameter, the importData method executes only when performed on certified documents. If you do not provide the parameter, the document does not need to be certified and the user is prompted to provide a location and file name.
Reference_Syntax.importData( [ STRING param ] )
param (Optional)
A valid string representing the location and name of the file from which the data will be imported. If you omit this parameter, a dialog box opens to let the user select the file manually.
Host Model

importData