Practical preservation: the PREMIS experience.(Preservation Metadata: Implementation Strategies)

ABSTRACT

In 9003 the Online Computer Library Center (OCLC) and Research Libraries Group (RLG) established an international working group to develop a common, implementable core set of metadata elements for digital preservation. Most published specifications for preservation-related metadata are either implementation specific or broadly theoretical. PREMIS (Preservation Metadata: Implementation Strategies) was charged to define a set of semantic units that are implementation independent, practically oriented, and likely to be needed by most preservation repositories. The semantic units will be represented in a data dictionary and in a METS-compatible XML schema. In the course of this work, the group also developed a glossary of terms and concepts, a data model, and a typology of relationships. Existing preservation repositories were surveyed about their architectural models and metadata practices, and some attempt was made to identify best practices. This article outlines the history and methods of the PREMIS Working Group and describes its deliverables. It explains major assumptions and decisions made by the group and examines some of the more difficult issues encountered.

INTRODUCTION

In 2003 the Online Computer Library Center (OCLC) and Research Libraries Group (RLG) established an international working group to develop a common, implementable core set of metadata elements for digital preservation. Most published specifications for preservation-related metadata are either implementation specific or broadly theoretical. PREMIS (Preservation Metadata: Implementation Strategies) was charged to define a set of metadata elements that are implementation independent, practically oriented, applicable to all types of materials, and likely to be needed by most preservation repositories. In addition, it aimed at establishing best practices for the implementation of preservation metadata.

The stated PREMIS objectives were to

* define an implementable set of "core" preservation metadata elements, with broad applicability within the digital preservation community;

* draft a data dictionary to support the core preservation metadata element set;

* examine and evaluate alternative strategies for the encoding, storage, and management of preservation metadata within a digital preservation system, as well as for the exchange of preservation metadata among systems;

* conduct pilot programs for testing the group's recommendations and best practices in a variety of systems settings;

* explore opportunities for the cooperative creation and sharing of preservation metadata.

It was intended that PREMIS would build on the earlier work of another initiative sponsored by OCLC and RLG, the Preservation Metadata Framework Working Group (OCLC, 2003). That group was convened in 2001-2002 to develop a framework outlining the types of information that should be associated with an archived digital object. Their report, A Metadata Framework to Support the Preservation of Digital Objects (OCLC/RLG, 2002), expanded the conceptual structure for the Open Archival Information System (OAIS) information model (Consultative Committee, 2002) and mapped preservation metadata elements to that conceptual structure. Although the framework proposed a list of metadata elements, it did not contain sufficient detail for an implementer to actually use the metadata in a preservation system without considerable further specifications. The PREMIS working group was established to take the previous group's work a step further: to develop a data dictionary of core metadata elements to be applied to archived objects, give guidance on the implementation of that metadata element set in preservation systems, and suggest best practice for populating those elements.

OCLC and RLG established the working group in 2003, chaired by Priscilla Caplan of the Florida Center for Library Automation and Rebecca Guenther of the Library of Congress. Because the charge was practical rather than theoretical, members were sought from institutions known to be running or developing preservation repository systems within the cultural heritage or information industry sectors. Conveners paid particular attention to diversity of stakeholders. The group consists of representatives from academic and national libraries, museums, and archives; governments; and commercial enterprises in six different countries. In addition, PREMIS includes an international advisory committee of experts periodically called upon to review progress and provide feedback.

In order to accomplish as much of the charge as possible in a reasonable timeframe, PREMIS divided into two subgroups with different deliverables and strategies. The Core Elements Subgroup took responsibility for drafting the "core" preservation metadata elements and supporting data dictionary. The Implementation Strategies Subgroup was responsible for examining alternative strategies for the encoding, storage, and management of preservation metadata within digital preservation systems and for developing pilot programs to test the group's recommendations in a variety of system settings.

The work of both subgroups was conducted almost entirely by weekly conference calls, which was a challenge given that the group members were from time zones ranging from the western United States to eastern Australia. Fortunately, only one person had to get up in the middle of the night to attend! However, the sheer frequency of calls and the ambitious agenda created a sense of camaraderie among participants. Members quickly learned each others' voices and mastered use of a wiki (a Web site that allows any user to add and edit content) set up for their use by the University of Chicago. The Core Elements Subgroup also held two face-toface meetings to expedite their work. The two meetings, one in San Diego in January…