E22 Man-Made Object Belongs to versions: Version 5.1.2Scope Note: This class comprises physical objects purposely created by human activity.
E71 Man-Made Thing Belongs to versions: Version 5.1.2Scope Note: This class comprises discrete, identifiable man-made items that are documented as single units.
E18 Physical Thing Belongs to versions: Version 5.1.2Scope Note: This class comprises all persistent physical items with a relatively stable form, man-made or natural.