sumo#time_interval  a time_interval has both an extent and a location on the universal timeline; a time_interval has no gaps, i.e. this class contains only convex time intervals
  closed_exclusion:  time_point
  supertype:  time_position  any time_point or time_interval along the universal timeline from negative_infinity to positive_infinity
  equal:  Time-Interval (pm)
  subtype:  Day
  subtype:  Week
  subtype:  Month
  subtype:  Year

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