less { hop { filter_eq { all_rows ; category ; helicopter } ; date } ; hop { filter_eq { all_rows ; category ; glider ( sailplane ) } ; date } } = true
select the rows whose category record fuzzily matches to helicopter . take the date record of this row . select the rows whose category record fuzzily matches to glider  sailplane  . take the date record of this row . the first record is less than the second record .