[graph1_on_time_measure
     [any time_measure,
          may be time of: a situation,
          may be duration of: a situation,
          may have for inferior_to: a time_measure,
          may be inferior_to of: a time_measure,
          may have for inferior_or_equal_to: a time_measure,
          may be inferior_or_equal_to of: a time_measure]
];