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Introduction to Digital Preservation: OAIS Reference Model

Subjects: Digital Library

Open Archival Information Systems Reference Model

The Open Archival Information Systems (OAIS) Reference Model is a conceptual model for a digital archive. Much of the terminology used in digital preservation comes from this model, which was turned into an ISO standard in 2002. The OAIS Reference model describes the environment, functional components, and information objects associated with a system responsible for the long-term preservation. As a reference model, its primary purpose is to provide a common set of concepts and definitions that can assist discussion across sectors and professional groups and facilitate the specification of archives and digital preservation systems. It has a very basic set of conformance requirements that should be seen as minimalist. OAIS was first approved as ISO Standard 14721 in 2002 and a 2nd edition was published in 2012. Although produced under the leadership of the Consultative Committee for Space Data Systems (CCSDS), it had major input from libraries and archives.

Six functional entities

There are six functional entities within the OAIS Archive. They each perform functions that carry out the sustainable operation of the archive. The six functional entities are:

Ingest: The processes the accept digital materials from Producers and prepare it for inclusion in the Archival Store.

Archival Store: The long-term storage and maintenance of digital materials. It ensures that archived digital materials reside in the right form of storage and that the bit streams of the digital materials remain complete and renderable over time.

Data Management: The maintenance of databases of descriptive metadata that identifying and describing the archived digital materials. It also manages the administrative data supporting the OAIS system operation, such as performance data or access statistics.

Access: The processes and the services that Consumers use to locate, request and receive information of digital materials in the Archival Store.

Administration: The day-to-day management of operations and the coordination of the other functional entities. It is also the central communications hub with the external environment: management, producers and consumers.

Preservation Planning: Monitoring of the external environment for changes or threats to the digital materials in the Archival Store. It maps our the preservation strategy and recommends appropriate revisions to it in line with changing conditions. This is the safeguard against a constantly evolving user and technological environment.

OAIS external environment

The OAIS archive operates within an external environment. There are three main stakeholders involved:

  • Management:The stakeholders responsible for the strategic planning and policy development for the OAIS archive.
  • Producers: The individuals, organizations or systems responsible for submitting and transferring SIPs for the creation of AIPs to be placed into (ingested by) the OAIS archive.
  • Consumers: The individuals, organizations or systems that locate, request and use the digital materials stored by the OAIS. A specific subset of Consumers is known as the "Designated Community".
    • Designated Community: An identified group of potential consumers who should be able to understand a particular set of information from an archive. These consumers may consist of multiple communities, are designated by the archive, and may change over time.

 

A stakeholder map for the OAIS archive. This includes producers, consumers and management

Information packages

There are three different types of information packages that move within the OAIS. At each stage they change, based on the digital files added (or removed) and the metadata created.

Submission Information Package (SIP): An Information Package that is delivered by the Producer to the OAIS for use in the construction or update of one or more Archival Information Packages (AIPs) and/or the associated Descriptive Information.

Archival Information Package (AIP): An Information Package, consisting of the complete set of digital files and a complete set of metadata for the AIP (to support preservation and access) that is preserved within an OAIS archive.

Dissemination Information Package (DIP): An Information Package, derived from one or more Archival Information Packages (AIPs), and sent by Archives to the Consumer in response to a request to the OAIS archive.

These information packages are what is known conceptually as a digital object. A digital object an aggregated unit of digital content comprised of one or more related digital files. These related files might include metadata, master files and/or a wrapper to bind the pieces together.