This is one of a series of guides produced by the Cedars digital preservation project. This guide concentrates on the technical approaches that Cedars recommends as a result of its experience. The accent is on preservation, without which continued access is not possible. The time scale is at least decades, i.e. way beyond the lifetime of any hardware technology. The overall preservation strategy is to remove the data from its medium of acquisition and to preserve the digital content as a stream of bytes. There is good reason to be confident that data held as a stream of bytes can be preserved indefinitely. Just as there is no access without preservation, preservation with no prospect of future access is a very sterile exercise. As well as preserving the data as a byte-stream, Cedars adds in metadata. This includes reference to facilities (called technical metadata in this document) for accessing the intellectual content of the preserved data. This technical metadata will usually include actual software for use in accessing the data. It will be stored as a preserved object in the overall archive store, and will be revised as technology evolves making new methods of access to preserved objects appropriate. There will be big economies of scale, as most, if not all, objects of the same type will share the same technical metadata. Cedars recommends against repeated format conversions, and instead argues for keeping the preserved byte-stream, while tracking evolving technology by maintaining the technical metadata. It is for this reason that Cedars includes only a reference to the technical metadata in the preserved data object. Thus future users of the object will be pointed to information appropriate to their own era, rather than that of the object's preservation. The monitoring and updating of this aspect of the technical metadata is a vital function of the digital library. In practice, Cedars expects that very many preserved digital objects will be in the same format, and will reference the same technical metadata. Access to a preserved object then involves Migration on Request, in that any necessary migration from an obsolete format to an appropriate current day format happens at the point of request. As well as recommending actions to be taken to preserve digital objects, Cedars also recommends the use of a permanent naming scheme, with a strong recommendation that such a scheme should be infinitely extensible.
Critical Arguements
CA "This document is intended to inform technical practitioners in the actual preservation of digital materials, and also to highlight to library management the importance of this work as continuing their traditional scholarship role into the 21st century."
This document provides some background on preservation metadata for those interested in digital preservation. It first attempts to explain why preservation metadata is seen as an essential part of most digital preservation strategies. It then gives a broad overview of the functional and information models defined in the Reference Model for an Open Archival Information System (OAIS) and describes the main elements of the Cedars outline preservation metadata specification. The next sections take a brief look at related metadata initiatives, make some recommendations for future work and comment on cost issues. At the end there are some brief recommendations for collecting institutions and the creators of digital content followed by some suggestions for further reading.
Critical Arguements
CA "This document is intended to provide a brief introduction to current preservation metadata developments and introduce the outline metadata specifications produced by the Cedars project. It is aimed in particular at those who may have responsibility for digital preservation in the UK further and higher education community, e.g. senior staff in research libraries and computing services. It should also be useful for those undertaking digital content creation (digitisation) initiatives, although it should be noted that specific guidance on this is available elsewhere. The guide may also be of interest to other kinds of organisations that have an interest in the long-term management of digital resources, e.g. publishers, archivists and records managers, broadcasters, etc. This document aimes to provide: A rationale for the creation and maintenance of preservation metadata to support digital preservation strategies, e.g. migration or emulation; An introduction to the concepts and terminology used in the influential ISO Reference Model for an Open Archival Information System (OAIS); Brief information on the Cedars outline preservation metadata specification and the outcomes of some related metadata initiatives; Some notes on the cost implications of preservation metadata and how these might be reduced.
Conclusions
RQ "In June 2000, a group of archivists, computer scientists and metadata experts met in the Netherlands to discuss metadata developments related to recordkeeping and the long-term preservation of archives. One of the key conclusions made at this working meeting was that the recordkeeping metadata communities should attempt to co-operate more with other metatdata initiatives. The meeting also suggested research into the contexts of creation and use, e.g. identifying factors that might encourage or discourage creators form meeting recordkeeping metadata requirements. This kind of research would also be useful for wider preservation metadata developments. One outcome of this meeting was the setting up of an Archiving Metadata Forum (AMF) to form the focus of future developments." ... "Future work on preservation metadata will need to focus on several key issues. Firstly, there is an urgent need for more practical experience of undertaking digital preservation strategies. Until now, many preservation metadata initiatives have largely been based on theoretical considerations or high-level models like the OAIS. This is not in itself a bad thing, but it is now time to begin to build metadata into the design of working systems that can test the viability of digital preservation strategies in a variety of contexts. This process has already begun in initiatives like the Victorian Electronic Records Stategy and the San Diego Supercomputer Center's 'self-validating knowledge-based archives'. A second need is for increased co-operation between the many metadata initiatives that have an interest in digital preservation. This may include the comparison and harmonisation of various metadata specifications, where this is possible. The OCLC/LG working group is an example of how this has been taken forward whitin a particular domain. There is a need for additional co-operation with recordkeeping metadata specialists, computing scientists and others in the metadata research community. Thirdly, there is a need for more detailed research into how metadata will interact with different formats, preservation strategies and communities of users. This may include some analysis of what metadata could be automatically extracted as part of the ingest process, an investigation of the role of content creators in metadata provision, and the production of user requirements." ... "Also, thought should be given to the development of metadata standards that will permit the easy exchange of preservation metadata (and information packages) between repositories." ... "As well as ensuring that digital repositories are able to facilitate the automatic capture of metadata, some thought should also be given to how best digital repositories could deal with any metadata that might already exist."
SOW
DC "Funded by JISC (the Joint Information Systems Committee of the UK higher education funding councils), as part of its Electronic Libraries (eLib) Programme, Cedars was the only project in the programme to focus on digital preservation." ... "In the digitial library domain, the development of a recommendation on preservation metadata is being co-ordinated by a working group supported by OCLC and the RLG. The membership of the working group is international, and inlcudes key individuals who were involved in the development of the Cedars, NEDLIB and NLA metadata specifications."
