rds whenever available and appropriate, avoiding proprietary data formats when possible. Even though standards change and evolve, they are much more stable and reliable than proprietary formats that may be tied to the commercial success of a single vendor. Given choices, for example, between digitizing video into MPEG, an international standard, and a proprietary format such as RealMedia or Windows Media, it makes sense to use the standards-based format. It often means creating a master copy in the standard format, and deriving from it proprietary versions that can be used by a wider audience. In one project that I'm involved with, or strategy involves digitizing video into MPEG-2 format for preservation, and generating RealMedia files to be used for end-user access.
While these and other methods can be used as informal guidelines, the issue of digital preservation really demands a more structured and formal approach. To this end, a number of efforts have taken place in recent years that provide a structured framework for the design of an archive that meets the requirements of long-term preservation in addition to other areas of functionality. The culmination of these efforts is the Open Archival Information System, or OAIS.
OAIS: A comprehensive framework for digital preservation
The complexities involved with changing technologies and the need to create permanent digital collections has sparked a number of initiatives of some of the major players. Some of the important activities in this arena include the CEDARS project in the UK (http://www.leeds.ac.uk/cedars/); NEDLIB, a collaborative project of several European national libraries (http://www.kb.nl/coop/nedlib/); and the National Library of Australia's PADI initiative (http://www.nla.gov.au/padi/). OCLC and the Research Libraries Group (RLG) have been collaborating on this issue and have issued a report titled: “Attributes of a Trusted Digital Repository: Meeting the Needs of Research Resources” (www.rlg.org/longterm/attributes01.pdf).
The most definitive model for creating long-lasting digital archives is known as OAIS, the Open Archival Information system. This model was developed by the Consultative Committee for Space Data Systems of NASA, and is under consideration for approval as an international standard. While developed for space data, the reference model is widely accepted as applicable to a very broad range of data types. The vocabulary and concepts specified in OAIS have become integrated into the language of the digital library community.
The official document that presents the OAIS reference model (www.ccsds.org/documents/pdf/CCSDS-650.0-R-2.pdf), is a long (148 pages) detailed document, written in terse, precise language, typical of other standards documents. I've found a couple of good summaries of the document that present the framework in understandable language. These include Brian Lavoie's “Meeting the challenges of digital preservation: the OAIS reference model” (OCLC Newsletter, No. 243 www2.oclc.org/oclc/pdf/news243.pdf) and the last section the OCLC/RLG report mentioned above.
The OAIS model places great emphasis on the long-term maintenance of digital collections. It recognizes that archives must deal with issues of changing technology and standards, taking into consideration the evolution of the computing environment. It offers strategies for dealing with the inevitable changes that will occur in operating systems, databases, and all the tools used to access digital information. Space doesn't allow me to describe the entire OAIS framework, but I do want to mention a few of its characteristics and some of its terminology. I encourage those involved in creating digital collections to take a closer look at this model, if they are not already familiar with it.
OAIS does not dwell on specific technologies, but rather focuses on the various relationships, concepts, and processes that apply to the overall problem of digital preservation. It is a comprehensive model or framework that addresses the issues related to designing an operating an archive t