a resource with a structureType of structureElement is an element contained with a structureBlock, but they are not part of a hierachy, thus they do not have a parentPart or childParts, they simply have a isPartOfStructureBlock property

Linked Data Metadata

dc11:description a resource with a structureType of structureElement is an element contained with a structureBlock, but they are not part of a hierachy, thus they do not have a parentPart or childParts, they simply have a isPartOfStructureBlock property
rdf:type http://scta.info/resource/structureType
rdfs:label Structure Element
rdfs:subClassOf http://scta.info/resource/structureType