Describes individual items held or distributed by the archive in connection with a study, group of studies, or resource packages. What constitutes an item is determined by the archive. Provides identification information on the item within the context of the archive including citation, a statement on its location, call number (internal identifier), URI, format, media type, and source. The item is classified by a study class designation, information on access restrictions, and availability status. Content information on the number of data files associated with the item, the completeness of the collection of objects represented by this item as well as descriptions of nested items are provided.