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The list of mapped items provides the functionality to remove the mapping for selected items.

Implications

Mapping collection vs Owning collection

The relation between an item and the collection in which it is mapped is different from the relation that this item has with the collection to which it was originally submitted. This second collection is referred to as the "owning" collection. When an item is deleted from the owning collection, it automatically disappears from the mapping collection. From within the mapping collection, the only thing that can be deleted is the mapping relation. Removing this mapping relation does not affect the presence of the item in the owning collection. 

Mapping an item does not modify access rights

When an item gets mapped into a collection, it does not receive new access rights. It retains the authorizations that it inherited from the collection that "owns" it. Collection admins who do not have read access to an item will not be able to map them to other collections.