ReadonlyeditorReadonlyfilledFillings (door / window id → opening id).
ReadonlyfillsOptional ReadonlyguidReadonlypartPart id → its assembly.
ReadonlypartsAssembly id → its IfcRelAggregates parts (a spatial container's children are not parts).
ReadonlyreadReadonlystoreReadonlystyledReadonlyvoids
Everything one batch of copies reads once: the live reader, the styles and the void / fill links of the model as it was before the batch.