Digital Libraries: It's Opening Day for METS

By Roy Tennant -- Library Journal, 5/15/2004

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In early April, about 100 librarians gathered at Stanford University for the second METS (Metadata Encoding and Transmission Standard) Opening Day. The first was held at the Library of Congress (LC) in October 2003. Designed as an opportunity to learn about METS, the meeting included demonstrations of how libraries are using this emerging standard. A third such session is scheduled for London on July 12, 2004.

The roots of METS go back to the beginning of digitization projects in libraries. Once you've scanned a book, what do you have? You have hundreds of individual digital files and no practical way to "bind" them all back together into an easily navigable whole. This is where METS comes in. METS provides a method to describe the structure of a digital object as well as encapsulate one or more packages of descriptive metadata, rights information, and information about how the item was digitized. METS provides a way to create a neat package of all the relevant files and metadata pertaining to a digital object. More important, it provides a standard way to package a digital object that can then be shared with other libraries, thereby promoting interoperability of digital objects.

METS objects can be just about anything—not just books. Libraries are already using METS to manage image, audio, and video files in addition to text documents of various kinds. And although METS records have so far been mostly used for digital objects, there is nothing in the standard that requires that the object being described be digital. Therefore, METS can be used to combine two or more different descriptive metadata packages while retaining the richness of the data in its native encoding.

From Ebind to METS

A 1996 attempt by UC-Berkeley to deal with this problem was Ebind, created by Alvin Pollock. Ebind provided a point of discussion for Berkeley and other institutions grappling with how to capture both the structure of an item and relevant metadata describing that item.

In 1998, a small group of U.S. universities, with Berkeley at the lead, embarked on "The Making of America II Testbed Project." An outcome of this National Endowment for the Humanities–funded effort was a white paper that described an architecture for digital objects ("The Making of America II Testbed Project: A Digital Library Service Model"). Other outcomes were a proposed new metadata format and a viewer for navigating digital objects using that metadata format. See the links list below for links; the web site for The Making of America II Testbed Project includes a demonstration.

This work led to reworking the metadata format into the emerging Metadata Encoding and Transmission Standard, an effort led by Jerome McDonough at New York University, chair of the METS Editorial Board. The board includes representatives from worldwide research libraries and organizations such as OCLC and RLG. LC serves as the maintenance agency and hosts the project web site.

Based on the evidence at METS Opening Day in April, METS is becoming popular in libraries because it solves a common problem (for examples see the METS Implementation Registry). But it was also clear that there remain a number of unresolved issues.

METS and FRBR, MPEG-21

One outcome was an awareness by the METS board that it should investigate the possible impact of the principles described in the International Federation of Library Associations and Institutions report "Functional Requirements of Bibliographic Records" (FRBR). FRBR is a structured framework for relating bibliographic records to the needs of users. No one is clear what impact, if any, FRBR might have on METS. But the board believes it would be better to consider any implications now rather than later.

Another issue is whether MPEG-21, an emerging standard that reportedly performs a role similar to METS, is better positioned to fulfill our needs. A component of the MPEG-21 standard is the Digital Item Declaration Language (DIDL), which at least one library has used successfully to encode information about digital objects (see the site "Using MPEG-21 DIDL…"). It's not yet proven that MPEG-21 can be successfully employed for all the purposes METS currently maintains. If it can, libraries could benefit from a much broader community of support.

But whether we use MPEG-21 or METS, a standard that provides a method to encapsulate all the information about an object—whether digital or not—is crucial. Publishers provide information about their books using the ONIX metadata standard. Librarians create MARC records for those books and perhaps eventually scan tables of contents or even the entire book. We need a way to capture all the files and metadata for a single intellectual object in a format that can be easily shared. Whether we develop our own standard, or help shape a standard outside our profession, it's a worthy and important goal.

LINK LIST
Ebind sunsite.berkeley.edu/Ebind/	Making of America II sunsite.Berkeley.edu/moa2/
The Making of America II Testbed Project: A Digital Library Service Model www.clir.org/pubs/abstract /pub87abst.html	METS www.loc.gov/standards/mets/
METS Implementation Registry sunsite.berkeley.edu/mets/registry/	Using MPEG-21 DIDL to Represent Complex Digital Objects in the Los Alamos National Laboratory Digital Library www.dlib.org/dlib/november03/ bekaert/11bekaert.html

Author Information

Roy Tennant (roy.tennant@ucop.edu) is Manager, eScholarship Web & Services Design, California Digital Library. He is author of Managing the Digital Library (Reed Business Pr., 2004)