Covering the Bases: Other Important Metadata in Digital Libraries

There are several other major forms of metadata with which you should be familiar. These resources will help to cover most of the bases:

MARC21 (MAchine-Readable Cataloging) is the current library standard for cataloging materials, and as such, is the one metadata most librarians are familiar with. One of the primary sources for digital library materials is library holdings, and these objects (usually books or journals) often have MARC records already. Familiarity with this standard is thus necessary for cross-walking the metadata into standards that better support digitized objects. Since MARC is a sequential metadata (often fed into computer systems in a single string with included counts of characters to indicate where various sections start or end), it requires specialized software. Therefore, the Library of Congress is developing MARCXML (MARC expressed in XML (Extensible Markup Language).
VRA Core, developed by the Visual Resources Association Data Standards Committee, is available in the stable version 3.0 as well as the version 4.0 Beta. This metadata is being developed to describe works of visual culture as well as the images that document them. In this context, a "work" is a physical entity, of which the images are simply representations.
MPEG-21/DIDL: Moving Pictures Experts Group Multimedia Framework / Digital Item Declaration Language, used for complex and multi-format digital objects. From the ISO description:
ISO/IEC 21000 (MPEG-21) (available here) defines an open framework for multimedia delivery and consumption, with both the content creator and content consumer as focal points. The vision for MPEG-21 is to define a multimedia framework to enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities.

The basic architectural concept in MPEG-21 is the Digital Item. Digital Items are structured digital objects, including a standard representation, identification and metadata. They are the basic unit of transaction in the MPEG-21 framework. More concretely, a Digital Item is a combination of resources (such as videos, audio tracks, images, etc), metadata (such as descriptors, identifiers, etc), and structure (describing the relationships between resources).

This second part of MPEG-21 (ISO/IEC 21000-2:2003) (available here) specifies a uniform and flexible abstraction and interoperable schema for declaring the structure and makeup of Digital Items. Digital Items are declared using the Digital Item Declaration Language (DIDL) and declaring a Digital Item involves specifying its resources, metadata and their interrelationships.

Within ISO/IEC 21000-2:2003 this Digital Item Declaration (DID) technology is described in four main sections:
- Model: The Digital Item Declaration Model describes a set of abstract terms and concepts to form a useful model for defining Digital Items.
- Representation: The Digital Item Declaration Language (DIDL) is based upon the terms and concepts defined in the above model. It contains the normative description of the syntax and semantics of each of the DIDL elements, as represented in XML. This section also contains some short non-normative examples for illustrative purposes.
- Schema: The complete normative XML schema for DIDL comprising the entire grammar of the DID representation.
- Detailed Examples: Illustrative (non-normative) examples of DIDL documents are provided to aid in understanding the use of the specification and its potential applications.
Schema files are available here. and I highly recommend two excellent articles on the topic:
- "Using MPEG-21 DIDL To Represent Complex Articles In The Los Alamos National Laboratory Digital Library", by Jeroen Bekaert, Patrick Hochstenbach, and Herbert Van de Sompel (D-Lib Magazine, November 2003, 9:11), and
- "Using MPEG-21 DIP and NISO OpenURL for the Dynamic Dissemination of Complex Digital Objects in the Los Alamos National Laboratory Digital Library", by by Jeroen Bekaert, Lyudmila Balakireva, Patrick Hochstenbach, and Herbert Van de Sompel (D-Lib Magazine, February 2004, 10:2).
FGDC: Federal Geographic Data Committee Metadata Standard, used for geospatial data, is more properly called The Content Standard for Digital Geospatial Metadata (CSDGM), Vers. 2 (FGDC-STD-001-1998). A user-friendly workbook is available, as well as other tools and publications Users should know that the ISO (International Standards Organization) has approved a new international standard for geospatial data, called the ISO 19115. As a member of the ISO, the US is required to revise the CSDGM in accordance with these new standards. More information about that is available here.
Advanced Distributed Learning has released the 3rd edition of SCORM (Sharable Content Object Reference Model) for developing, packaging, and delivering learning objects. This specification was developed in conjunction with IEEE (Institute of Electrical and Electronics Engineers) Learning Technology Standards Committee, IMS (Instructional Management Systems) Global Learning Consortium, AICC (Aviation Industry Computer-Based Training Committee), and Ariadne Foundation. SCORM has three major components: content packaging, run-time communications, and course metadata. An online tutorial is available.

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This information is provided without guarantees as to validity or completeness, particularly in light of the fact that the world of metadata in digital libraries is a world of shifting sands, constantly changing.

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