RDF representation can model "closed" or "open" collection of containers of an item. In an integrated system, one can collect a complete or closed list of containers, each of which contains the item in question. For the WWW, the list of containers of an item needs to be an open collection since there is no way to ascertain that the collection represents a complete list. This is typically the case when sioc:has_container property is inferred from its inverse property sioc:container_of, i.e. one may not know all containers in all WWW sites that refer to the item.

ICOM's object-oriented representation should include similar differentiation of closed or open collections. ICOM objects may include a construct to explicitly represent open collections (as dynamic queries/searches) in addition to the regular closed collections (as attributes).

ICOM RDF representation did not use RDF collections, so avoided the issue of representing closed or open collections. ICOM RDF uses properties and cardinality "multiple" to represent sets.

ICOM specification introduced an optional property definition in Item class to represent multi-containment relation:

Class name: icom:Item
Property name: icom:container
Description: Zero, one, or more containers of an item.
Required: False
Inherited: False
Property Type: icom:Container
Cardinality: Multi
Updatability: Read Write