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Digital Archives

November 8th, 2005 · No Comments · Digital Preservation, Terms & Definitions

A digital archives is a repository that stores one or more collections of digital information objects with the intention of providing long-term access to the information. A digital archives can be a sophisticated, multi-tiered storage system or simply a C:\ drive on someone’s home computer.

‘Long-term’ refers to a period of time which is long enough to be concerned about the impacts of changing technologies, including support for new media and data formats, and with a changing user community, on the information being held in a repository. This period extends into the indefinite future.

Ensuring long-term access to digital information is a complex challenge that includes issues such as:

  1. storage media instability and deterioration
  2. technology obsolescence and incompatibility (at the level of: hardware, system software, application software, data and file formats, storage media readers and drivers)
  3. lack of metadata which results in the failure to locate information, the inability to render and read the information, or the inability to attribute meaning or value to the information due to the lack of contextual information
  4. lack of clearly assigned responsibilities and resources for long-term preservation

Cornell University Library provides a good introduction to these issues as well as a basic tutorial on digital preservation.

The Open Archival Information System (OAIS) model (ISO standard 14721) is a high-level reference model that is being used by organizations world-wide to build further understanding, consensus, and interoperability for organizations that are implementing digital archives to address digital preservation issues.

The OAIS presents a comprehensive logical model describing all of the roles, functions and entities of a typical digital archives without committing to specific technologies, methodologies or management frameworks.

Open Archival Information System - reference model

OAIS Responsibilities

The primary concept in the OAIS is that of an ‘archival information system’ which is defined as “an organization of people and systems that has accepted the responsibility to preserve information and make it available for a designated community.” It establishes six primary responsibilities that must be met:

  1. Negotiate for and accept appropriate information from information producers.
  2. Obtain sufficient control of the information in order to meet long-term preservation objectives.
  3. Determine the scope of the archive’s user community.
  4. Ensure that the preserved information is independently understandable to the user community, without requiring the assistance of the information producer.
  5. Follow documented policies and procedures to ensure the information is preserved against all reasonable contingencies, and to enable dissemination of authenticated copies of the preserved information in its original form, or in a form traceable to the original.
  6. Make the preserved information available to the user.

OAIS Roles

There are three primary roles in the OAIS model: management, producer and consumer.

  1. Management’s responsibilities include formulating, revising, and in some circumstances, enforcing, the high-level policy framework governing the activities of the digital archives.
  2. Producers submit the information objects to be preserved, along with associated metadata, to the digital archives via an ingest process, which accepts the submitted information and prepares it for inclusion in the archival store.
  3. Consumers are the individuals, organizations, or systems expected to access and use the information objects preserved by the digital archives.

OAIS Functions

The OAIS is organized into 6 high-level functions or services.

  1. Ingest is the set of processes responsible for accepting information submitted by Producers and preparing it for inclusion in the archival store.
  2. Archival Storage is the function of the system that manages the long-term storage and maintenance of digital materials entrusted to the digital archives.
  3. The Data Management function maintains databases of descriptive metadata identifying and describing the archival material in support of the digital archives access aids. It also manages the administrative data supporting the digital archives’ internal system operations, such as system performance data or access statistics.
  4. Preservation Planning is the service that is responsible for mapping out the digital archives’ preservation strategy, as well as recommending appropriate revisions to this strategy in response to evolving conditions in the digital archives’ environment.
  5. The Access function manages the processes and services by which Consumers locate, request, and receive delivery of objects residing in the archival store.
  6. The Administration function is responsible for managing the day-to-day operations of the digital archives, as well as coordinating the activities of the other five high-level services.

OAIS Information Packages

The entities within the OAIS are based on the concept of an information package: a conceptualization of the structure of information as it moves into, through, and out of the digital archives. An information package consists of the digital information object that is the focus of preservation, along with metadata necessary to support its long-term preservation and access, bound into a single logical package.

The OAIS recognizes three primary types of information packages:

  1. The Submission Information Package (SIP), is the version of the information package that is transferred from the Producer to the digital archives when information is ‘ingested’.
  2. The Archival Information Package (AIP) is the version of the information package that is stored and preserved by the digital archives. The AIP consists of the information that is the focus of preservation, accompanied by a complete set of metadata sufficient to support the digital archives’ preservation and access services.
  3. The Dissemination Information Package (DIP) is the version of the information package delivered to the Consumer in response to an access request.

Within the context of my research topic, I am primarily interested in the services provided as part of the Access function of digital archives. I have used the term ‘archives access systems’ to distinguish it as that component or sub-system within a digital archives that makes the Access service available.