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A primary goal of this model is to avoid the local copying and duplication of metadata. Whenever possible there should be reference (i.e. link) made to an authoritative record. The local system should only retain a minimal set of core metadata relating to the item. Whenever the full, rich set of metadata are required, these should be retrieved dynamically from the authoritative source (e.g. knowledge base). Furthermore, the locally retained core metadata should only be present in the local Folio system when it is needed. For electronic items this implies that local placeholders are only present once an item has been accessed. In other words, it is access which converts an entitlement (a potential holding) into an actual holdings which may then be represented within the local Folio system.
https://discuss.folio.org/t/resource-management-data-domains-diagram/724