List of Used OCFL Extensions

In our workshop scenario, various official and tool-specific (NNNN-) extensions are used. These can be categorized by their location of use and function.

1. Storage Root Extensions

These extensions control the behavior of the entire storage root (the storage layout of the objects).

initial: Determines which extension is loaded first at startup (usually points to the extension-manager).
NNNN-gocfl-extension-manager: A meta-extension of gocfl that coordinates other extensions and manages documentation files, for example.
0004-hashed-n-tuple-storage-layout: Defines the mapping of object IDs to directory structures using hashing (standard in this workshop).

2. Object Extensions

These extensions are active within the individual OCFL objects. We divide them here by their primary purpose:

A. Path and Layout Extensions

These extensions determine how files are physically stored and named within the object.

0011-direct-clean-path-layout: Cleans up filenames for maximum system compatibility (e.g., replacing spaces with =u0020). For details, see Object Structure.
NNNN-content-subpath: Splits the content directory into logical areas such as data/ (user data) and metadata/ (generated data). For details, see Object Structure.

B. Metadata Extensions

These extensions automatically enrich the object with technical or administrative metadata during the ingest process.

NNNN-indexer: Extracts technical metadata (format, duration, resolution, etc.) using tools like Siegfried and FFMPEG and stores it in indexer_v1.jsonl.gz.
NNNN-filesystem: Backs up metadata of the original filesystem (timestamps, permissions) in filesystem_v1.jsonl.gz.
NNNN-metafile: Allows including custom metadata (like our info.json) when creating the object.
0009-digest-algorithms: Enables the calculation of additional checksums (fixity) for long-term integrity, as OCFL only allows SHA-512/256 by default.

C. Extensions for Better Readability and Preview

These extensions serve to make the content of the object more quickly graspable for human users.

NNNN-thumbnail: Automatically generates small preview images for images, videos, and PDFs, which are stored in the metadata/thumbnails/ folder.

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