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The content that Fedora persists (user and system files) is a complete representation of the repository. These files are written to OCFL objects within a top-level storage hierarchy. This section describes the storage hierarchy layout and the algorithm for mapping an OCFL object identifier to its storage hierarchy path.

Unless configured otherwise, Fedora uses the default configuration of the "OCFL Community Extension 0003: Hashed Truncated N-tuple Trees for OCFL Storage Hierarchies" (0003-hashed-n-tuple-trees). That configuration is:

{
    "digestAlgorithm": "sha256",
    "caseMapping": "toLower",
    "tupleSize": 3,
    "numberOfTuples": 3,
    "shortObjectRoot": false
}

The SHA-256 hash of Fedora resource's ID is calculated, converted to lowercase, then split into three-character segments. The first three segments are used in creating the first three levels of directories below the OCFL storage root. The OCFL object is persisted within a fourth-level directory, which is the entire, lowercase, SHA-256 value previously calculated. The extension definition provides an example.

Specification of Fedora-specific OCFL Files

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