#water_level  the level of the surface of a body of water
  subtype:  #sea_level  level of the ocean's surface esp that halfway between mean high and low tide; used as a standard in reckoning land elevation or sea depth
  supertype:  #elevation  distance of something above a reference point
     supertype:  #distance  the property created by the space between two objects or points
        supertype:  #spatial_arrangement__spatialarrangement__spacing  the property possessed by an array of things that have space between them
           supertype:  #placement.position__arrangement  the spatial property of the way in which something is placed: "the arrangement of the furniture"; "the placement of the chairs"
              supertype:  #spatial_relation__spatialrelation__position__spatial_property__spatialproperty  the spatial property of a place where or way in which something is situated; "the position of the hands on the clock"; "he specified the spatial relations of every piece of furniture on the stage"
                 supertype:  #relation  an abstraction belonging to or characteristic of two entities or parts together
                    supertype:  pm#thing_that_can_be_seen_as_a_relation  usable as relation type
                       supertype:  pm#thing_playing_some_role  category to classify things according to roles/viewpoints; classification under this category is application-dependant
                          supertype:  pm#thing__something___T__t___3D_or_4D_thing_or_anything_else  any category (type or individual) is instance of this type; any type is also a subtype of this type

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