Mapping to Records in Context Ontology

[Nils Weinander]

I am working on mapping data from the main archival database at the National Archives of Sweden to the Records in Context Ontology. 

https://www.ica.org/standards/RiC/ontology.html

The upper levels of the hierarchy of archival information is straight forward. We have objects which map to rico:RecordSet, with rico:hasRecordSetType => ric-rst:Fonds and ric-rst:Series respectively.

At the "leaf" level, objects like photos, maps and drawings are also straight forward. They map to rico:Record, with rico:hasContentOfType => suitable resources specifying the object type. The objects with the type Volume in the archival database are trickier. They represent once or more documents collected in a box or bound in a book. I can see the rationale to map these to rico:RecordSet with  rico:hasRecordSetType  => ric-rst:File, but this would mean there would be RecordSets with no Record content as we don't have any data for the individual documents within the volume. As far as I can see from the ontology there is no rule saying that RecordSets must have rico:WholePartRelation to one or more Records. Am I reading this correctly?