The Open Archival Information System (OAIS) is a core standard for digital preservation systems. OAIS, an ISO standard since 2003 (ISO 14721:2003 OAIS), specifies the terms, concepts, and reference models for a system dedicated to preserving digital assets for a designated community.
The main OAIS concept relevant to storage is the Archival Information Package (AIP), depicted in the figure below. An AIP contains the content information, including the Content Data Object or raw data which is the focus of the preservation, as well as the recursive Representation Information (RepInfo) needed to render the object intelligible to its designated community. The representation information may include information about the hardware and software environment needed to view and interpret the content data object.
The other part of an AIP is the Preservation Description Information (PDI), which is further divided into four sections:
- Reference globally unique and persistent identifiers for the content data object
- Provenance chain of custody, the history and the origin of the content information custody
- Context relationships of the content information to its environment
- Fixity a demonstration that the particular content information has not been altered in an undocumented manner
Note that the RepInfo is a recursive object and may have additional RepInfo to interpret it. This recursion ends when facing a RepInfo that is non-digital and will be preserved by the designated community. For example, a text document represented in an Open Document Format (ODF) file is associated with RepInfo that includes the ODF specification. Assuming the ODF specification is in XML, its RepInfo includes the XML specification, and the latter is associated with a RepInfo that includes the Unicode specification. We assume that the Unicode specification is preserved by the designated community and thus it doesn't need more RepInfo.