Introduction to Digital Preservation – intro video 43min
Digital Preservation Management
Implementing short-term strategies for long-term problems
Obsolescence (‘veraltet’) & Physical Threats
Information created and stored digitally is at risk for loss in two important ways: obsolescence and physical damage. Obsolescence can affect all facets of the archival storage function, including hardware, software, and even the arrangement of the data in a stored file. The damaging effects of obsolescence can occur in an alarmingly fast pace. Digital information is also vulnerable to physical threats. Like obsolescence, physical damage can occur to multiple components required to create, store, and access digital information, namely hardware and media.
As in most rapidly changing fields, the terminology of digital preservation is fluid, with some terms having multiple meanings and others evolving over time. There are online glossaries that offer general definitions of digital preservation terminology. Because this tutorial is structured around two foundation documents—the Reference Model for an Open Archival Information System (OAIS) and Attributes of a Trusted Digital Repository (TDR)—we present here definitions of key terms that are critical to understanding that context. These foundation documents arose from very different communities and sometimes use different terms to describe the same concept. Any such divergences will be indicated.
Since the final versions of TDR and OAIS were released in 2002, the digital preservation community has produced a number of documents that have contributed to the definition and evolution of core terms and concepts, including: the Producer-Archive Interface Methodology Abstract Standard (PAIMAS), Trusted Repositories Audit & Certification (TRAC), PREservation Metadata: Implementation Strategies (PREMIS), and the Final Report of the Blue Ribbon Task Force on Sustainable Digital Preservation and Access. We’ve included these publications in a list of additional readings with top recommended resources and more food for thought.
The Open Archival Information System (OAIS) Reference Model
Introductory Guide (2nd Edition)
Abstract: Originally developed as part of a broader effort to develop formal standards for the long-term storage of digital data generated from space missions, the Open Archival Information System (OAIS)has since formed the foundation of numerous architectures, standards, and protocols, influencing system design, metadata requirements, certification, and other issues central to digital preservation. This Technology Watch Report traces the history, salient features, and impact of the OAIS reference model. It is suitable both as a gentle introduction to OAIS for those new to the reference model, or as a resource for practitioners wishing to re-acquaint themselves with the basics of the model and subsequent developments. The report concludes with a brief discussion of OAIS’s key benefits and limitations, drawn from the model’s legacy of more than a decade of use in the digital preservation community.
Executive Summary
The Consultative Committee for Space Data Systems (CCSDS) initiated work aimed at developing formal standards for the long-term storage of digital data generated from space missions. Part of this effort involved the development of a reference model for an ‘open archival information system’ (OAIS). The reference model would represent a comprehensive and consistent framework for describing and analysing digital preservation issues, provide a sound footing for future standards-building activity, and serve as a point of reference for vendors interested in building digital preservation products and services. The OAIS reference model was approved in January 2002 as ISO International Standard 14721; a revised and updated version as published in 2012 as ISO Standard 14721:2012.The central concept in the reference model is that of an open archival information system.
An OAIS-type archive must meet a set of six minimum responsibilities to do with the ingest, preservation, and dissemination of archived materials. An OAIS-type archive operates in an environment populated by three types of entities: Management, Producer, and Consumer. A special class of Consumer is called the Designated Community: the subset of Consumers expected to independently understand the archived information in the form in which it is preserved and made available by the OAIS. An OAIS-type archive’s external environment could also include interaction with other OAIS archives.
The reference model identifies and describes the core set of mechanisms with which an OAIS-type archive meets its primary mission of preserving information over the long term and making it available to the Designated Community. These mechanisms are summarized by the OAIS functional model, which defines six high-level services, or functional entities, that collectively define the OAIS’s preservation and access operations: Ingest, Archival Storage, Data Management, Preservation Planning, Access, and Administration. Operating alongside these six functional entities are Common Services, which consist of basic computing and networking resources. An OAIS-type archive will implement each of the six functional entities, along with Common Services, in the course of building a complete archival system. The reference model provides a high-level description of the information objects managed by an OAIS-type archive. The OAIS information model is built around the concept of an information package, which consists of the object that is the focus of preservation, along with metadata necessary to support its long-term preservation, access, and understandability, bound into a single logical package. There are three important variants of the information package concept: the Submission Information Package (SIP), the Archival Information Package (AIP), and the Dissemination Information Package (DIP). The AIP is the information package variant which the OAIS is committed to perpetuate over the long term. Construction of the AIP begins with the Content Data Object – the information that is the focus of preservation. The Content Data Object is accompanied by Representation Information: information necessary to render and understand the bit sequences constituting the Content Data Object. The Content Data Object and its associated Representation Information are collectively known as Content Information. Long-term retention of the Content Information requires additional metadata to support and document the OAIS’s preservation processes. This metadata is called Preservation Description Information, or PDI. PDI consists of five components:1) Reference Information; 2) Context Information; 3) Provenance Information; 4) Fixity Information; and 5) Access Rights Information. Packaging Information binds Content Information and Preservation Description Information into a single logical package; Descriptive Information supports the discovery and retrieval of Content Information by an OAIS’s Consumers. The OAIS reference model includes a discussion of different classes of interoperability across OAIS-type archives: independent archives, cooperating archives, and federated archives. The reference model also notes that archives can interoperate through shared functional areas.
A number of initiatives have used the OAIS reference model as a conceptual foundation and starting point for more focused work in digital preservation. Areas of application include, but are not limited to, ‘OAIS-compliant’ repository architectures and systems; repository self-assessment and certification; metadata requirements for digital preservation; methods and protocols for encoding and exchanging archived information; and other OAIS-related standards. Because the reference model is a conceptual framework rather than a blueprint for concrete implementation, the meaning of ‘OAIS-compliant’ is necessarily vague and open to interpretation. A key element in the design of OAIS is its flexibility and level of abstraction: it makes no assumptions about how the concepts and models in OAIS are to be implemented, and imposes no requirements concerning the technologies used to support the implementations. Despite the attendant ambiguity, the notion of OAIS conformance has been beneficial, to the extent that it helps consolidate understanding of the fundamental requirements for securing the long-term persistence of digital materials–a necessary condition for building well-understood, interoperable, and ultimately, trusted digital preservation systems. Perhaps the most important achievement of the OAIS reference model to date is that it has become almost universally accepted as the lingua franca of digital preservation, shaping and sustaining conversations about digital preservation across disparate domains, and supplying a general mapping of the landscape that stewards of our digital heritage must navigate in order to secure the long-term availability of digital materials. Alignment with concepts defined in OAIS helps orient a technical implementation, draft standard, or other activity within the broader repository context that the OAIS reference model defines, making it part of a cohesive ’big picture’. It seems reasonable to conclude that OAIS has become a foundation resource for understanding digital preservation, a language for talking about digital preservation issues, and a starting point for implementing digital preservation solutions. It is possible to identify a few limitations associated with OAIS’s impact. Very few of its concepts have been directly and formally operationalized as standards in their own right. A design, a protocol, even a standard can self-declare itself OAIS-conformant (but without an explicit accounting of how conformance is actually manifested). Initiatives can use OAIS concepts as a means of labelling or describing various components within their structure (but these concepts can be used quite superficially, more as an expositional shorthand rather than a detailed mapping); OAIS can be cited as a foundation or starting point for a particular initiative, or alternatively the initiative can declare itself informed by OAIS (but without necessarily any elaboration on how this was so). It is useful to remember that an OAIS-type archive is still one built primarily on OAIS concepts, not an OAIS suite of standards. The digital preservation community would benefit from a careful assessment of where more precise and authoritative definitions of OAIS concepts and relationships would accelerate progress in achieving robust, widely applicable, and interoperable digital preservation solutions.
NDSA Levels of Digital Preservation: 2019 UPDATE
The Levels of Digital Preservation (LoP) is a resource for digital preservation practitioners when building or evaluating their digital preservation program. Originally created in 2013, Version 2.0 was released in 2018 along with additional supporting documentation and resources.
MS Instructional Design 