Each parameter has a default value, which is used if no parameter is specified on the command line. A parameter may be either mandatory or optional. The default value and mandatory attribute are specified in the parameter file.
A mandatory parameter must be explicitly given on the command-line, otherwise an error message will be printed to prompt the user to re-enter the command. If an optional parameter is not specified, the default is used.
Note: Mandatory parameters have a default value for use in the GUI. The GUI assigns values to all parameters and does not treat mandatory parameters specially.
