Outer OAIS – Inner OAIS proposal

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Compiled from blog Outer OAIS - Inner OIAS for distribution aspects and comments to section Archive Interoperability - should reference OO-IO model.

Registered on the OAIS review wiki (http://review.oais.info) in issues:

Originally the below headers correspond to fields on submission from via http://review.oais.info

Product: (from selected product)

OAIS June 2012

Reporter: (from login)


Component: (from list)

Section 6: Archive Interoperability

Component Description (fixed from selection of 'Component'):

Introduce an OAIS which may be geographically distributed but with all parts under the same Management.

Version: (from selected product)

June 2012

Category of change: (from list)

Updates to add missing concepts or strengthen weak concepts

Are there issues of backward compatibility?: (from list)


Is this a conformance issue?: (from list)



Interoperability for distributed digital preservation, can be expressed and analyzed by viewing (Outer) functional entities as fully or partly described by one or more Inner OAIS. In this case part of functions related to the distributed aspects covered by the Inner OAIS are covered there rather than in the (Outer OAIS) functional entities. An example is collaborative bit preservation which can be expressed as an Inner OAIS of the (Outer) Archival Storage/Preservation Storage. In this case e.g. preservation planning and history recording of media migration are covered by the Data Management and Preservation Planning within the Inner OAIS, and thus not part of the Data Management and Preservation Planning of the (Outer) OAIS.

Description of requested change:

(Use From: "..." To "..." format)

Add as 5th bullet in introduction of section 6.1:

  • Distributed digital preservation: Archives that have entered into agreements with other Archives to manage functions as part of conducting distributed digital preservation (the use of replication, independence, and coordination to address the known threats to digital content through time to ensure their accessibility resources) in a way that does not alter the user community’s view of the Archive.

Add section after Section 6.1.4
<The text and figures given in attached document>

[D13] "Supporting Analysis and Audit of Collaborative OAIS’s by use of an Outer OAIS – Inner OAIS (OO-IO) Model" by Eld Zierau and Nancy McGovern. In Proceedings of of the 11th International Conference on Preservation of Digital Objects (iPres) 2014, pp. 209-218. Available at https://fedora.phaidra.univie.ac.at/fedora/get/o:378066/bdef:Content/get
[D14] "Creating a Framework for Applying OAIS to Distributed Digital Preservation" by Eld Zierau and Matthew Schultz. In Proceedings of the 10th International Conference on Preservation of Digital Objects (iPres) 2013, pp. 78-83, Lisbon. Available at http://purl.pt/24107/1/
[D15] "Cross-Institutional Cooperation on a Shared Bit Repository" by Eld Zierau and Ulla Bøgvad Kejser, TERI Press, New Delhi, Journal of the World Digital Libraries, vol. 6, issue 1
[D16] "The Outer OAIS-Inner OAIS (OO-IO) Model" by Eld Zierau and Nancy McGovern – to be published in 2017



<File will have contents as given in section "Attachment File contents" below>



Organisation of the submitter:

The Royal Library of Denmark (reviewed via OAIS Community)

Explanation of the reason for the suggested change:

Distribution is crucial for digital preservation, and OAIS is not strong on this aspect. The OO-IO model has proven to be a useful way to explain distributed digital preservation within OAIS, thus the OAIS will be stronger, up-to-date and more useful if it includes the OO-IO model. As explain in the iPres 2014 paper mention attached description the OO-IO model has evolved within the digital preservation community needing distributed digital preservation.

Note that the figures in the attachment are following other suggestions and may need adjustments according to decisions on whether to include these other suggestions (Preservation Storage instead of Archival Storage, Visual OAIS – Symbols for functional entities, Visual OAIS – re-introducing coulours for functional entities).

Note also that the exact reference for the OO-IO model will be provided as soon as possible, but cannot be provided here as it has not been published yet.

Attachment File contents:

A helpful way to describe interoperability for distributed digital preservation is to use the Outer OAIS – Inner OAIS model (the OO-IO model) [D13,D14,D15,D16]. This model can support the analysis and audit of collaborative arrangements between multiple OAIS’s, where OAIS’s is used as the plural form of an OAIS.

The OO-IO model is depicted below in a full version:

An example of using the OO-IO model for an OAIS basing bit preservation on a solution with distribution of replicas is illustrated in the following figure:

In this example, the Inner OAIS (PS) IO the OAIS covers coordination and handling of each replica, and the Inner-Inner OAIS’s (PS-PS) IIO 1,2, … that cover handling of each their replica. Viewing a functional entity as an Inner OAIS can assist in

  • analysis of stakeholders requirements
  • provision of terminology
  • analysis of interfaces
  • analysis of audit points

For example audits of the OAIS will include audits of each of the Inner OAIS’s (and Inner-Inner OAIS’s) for the parts of the functional entities that there are agreed to cover.

So far the most elaborate use cases has been for Preservation Storage (Archival Storage) - especially when describing all aspects of distribution in more organizations/platforms etc. as well as all OAIS aspects of bit preservation. The Ingest case is also becoming increasingly relevant in cases where the creation of a final AIP is spanning over long periods, and thus the SIP needs to be secured as an Inner OAIS AIP of the Ingest functional entity.

The Ingest case is also becoming increasingly relevant – where an inner OAIS that takes care of the immediate preservation of material, where the time of the actual generation of AIPs for long term preservation is long. That means the time interval (e.g. a year), where material cannot be assumed to be resubmitted, and where the material is at risk of getting lost if only ordinary backup facilities are used.

One of the implicit consequences of distribution in digital preservation, is the need for coordination among collaborators. Establishment and performance of this coordination is crucial for ensuring sustainability of the overall organizational endeavor.