Purpose: Identification of a core set of metadata elements to be used in the development, testing, and implementation of multiple repositories.

Background: With a charter from the Digital Futures Group at the Library of Congress, representatives from Library Services, ITS and the National Digital Library Program drafted this list of elements drawing on previous work contained in Structural Metadata Dictionary for LC Digitized Material, version 1.03, and Metadata Table for the Coolidge-Consumerism Experiment, and on experience with the Thomson Editorial Asset Management System (TEAMS) repository proof-of-concept project, December 1998-April 1999. After broader discussion and comment during summer 1999, some nomenclature was modified, elements for audio-visual objects were added to the list and a distinction was made between information necessary for digital preservation and for digital reformatting. An application of the core metadata elements for audio visual materials is currently in development as part of the Audio Visual Preservation Digital Prototyping Project.

Types of Metadata: Metadata elements listed in the table are categorized according to three types: descriptive, administrative, and structural. Administrative metadata is used for managing and preserving objects in the repository; structural metadata is used primarily for storage of objects in a repository and for presentation; descriptive metadata is used for discovery of objects. The elements defined in this table are to support structural and administrative functions. Functions served are access management, administration, discovery, persistent identifier, presentation, digital preservation and preservation reformatting.

The Library intends to maintain the fullest descriptive metadata in its main catalog. Experiences with the Coolidge-Consumerism experiment and the TEAMS prototype, however, indicate that some descriptive information is helpful for administration of metadata and presentation of content. Consquently, five descriptive elements are included in the Table of Core Metadata Elements.

Metadata Levels: A hierarchy of information is proposed to accommodate the diversity of digital objects and to propagate data with some efficiency. Metadata elements may be supplied at multiple and various levels. Nesting of objects is expected and will be further clarified during the pilot phase of metadata capture and deposit. Information may be inherited from parent levels or may be specific to single objects at a lower level. For example, a collection may have general access rights but some of its items may be restricted. The access_rights attribute value on the collection (set or aggregate level) may be "public," but a single title(primary object level) in the collection may be "restricted."

The levels of metadata are

• Set - Set-level metadata applies to what is currently known as a digital collection, e.g. Alexander Graham Bell Family Papers. Digital collections are formed from aggregates that group digital items by original content type, such as non-motion visual, text, motion visual, or audio; and by custodial responsibility as well as by collection. A collection may be determined from an archival series or from a topical bibliography. Some digital collections are contained within a single aggregate. Others are formed by numerous aggregates. Set-level metadata applies to all aggregates within the set regardless of content or responsibility.
• Aggregate - An aggregate organizes digital objects by digital type and by digital custodial responsibility. A single aggregate may be a digital collection. Aggregate-level metadata applies to all primary objects within an aggregate.
• Primary Object - The specific item identified by the online collection access aid as a coherent whole is known as the primary object. Primary objects are usually the digital equivalents of physical library items, such as a book, a sound recording, a movie, a single title of sheet music, a folder of letters, a photograph, or a map. This level metadata applies to all the intermediate and terminal objects of a particular primary object.
• Intermediate Object - The intermediate object is a view or component of the primary object. A book that can be presented as page images or as searchable text has two intermediate objects. One points to all the page images of the book, the other to an encoded text file. Complex primary objects such as sound recordings offer many intermediate object possibilities. Multiple sides or tracks for a recording, each with sound and label components, may be captured in several formats. A single78 rpm record with two sides will have several audio files in both streaming and higher resolution formats, as well as the image and text of the label for each side and the jacket or album cover.  Metadata for an intermediate object allows the gathering of digital files and metadata for the creation of presentations.
• Terminal Object - The terminal object is the digital content file or files that form the object. There is at least one terminal for each object. Terminal object-level metadata is primarily structural supplying the digital attributes of each file such as size, extension, bit-depth, etc.

• Name is the label for the metadata element. Names are intended to be easily comprehended and unambiguous.
• Definition is a brief description of the information contained in the element.
• Function is an indicator of how the element is used. Functions served by metadata elements are access management, administration, discovery, persistent identifier, presentation, digital preservation and preservation reformatting. Preservation (D) signifies digital preservation and preservation (R) indicates preservation reformatting.
• Type is an indicator of the functions the metadata is intended to support.
• Use is an indicator of frequency and requirement of the element.
• Level is an indicator of position within the repository hierarchy that the element is meaningful.