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Guiding Principles

Long term preservation can be considered a relay of content over time, a series of hand-offs occurring repeatedly at many levels: between types of media and storage systems, object frameworks and software systems, different institutions and policy regimes, and different communities. As time passes, all links to the original creators and context will be severed, exacerbating the challenges. The National Geospatial Digital Archive (NGDA: [1] ) has identified three architectural design principles beyond OAIS ("Reference Model for an Open Archival System (OAIS)": [2]) which are necessary to preserve content over time: the "relay" principle, the "fallback" principle, and the "resurrection" principle.

The "relay" principle states that a preservation system should support its own migration.

In the event that the system itself is no longer functional, then a preservation system should support some form of hand-off of its content (this is the "fallback" principle).

Since the costs of continued migration of content is very high, a method of mitigating that cost is to allow content to become obsolete, but to support sufficient metadata and contextual information to be able to resurrect full access and use at some future time (the "resurrection" principle). Preserving any type of digital information requires preserving the information's context so that it can be interpreted correctly.

Given that at the time of discovery, the file system itself may be obsolete, one potentially important task is storing inode information and information about the parameters of the file system (type of partition support needed, for example) at the top level in a plain text or XML manifest. Some information that should be included are then number and type of characters (Unicode? Latin 1?) allowed in file names, and other expectations for support. Another suggestion was to ensure that each level contains a manifest describing what is at the level below it and how these contents relate. Potentially, the entire file system could be zipped up and included with a manifest for submission into a preservation storage system hosted elsewhere.

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