OCFL is an open standard for storing digital objects in a repository-independent and preservation-friendly format. It aims to ensure completeness, parsability, robustness, versioning, and storage diversity. The standard was developed through an open community process and draws on existing digital preservation best practices. An OCFL storage root contains digital objects and their metadata and versions arranged in a filesystem structure. The standard is now in version 1.0 along with implementation notes and validation tools.

1. OCFL v1.0 – The Oxford
Common File Layout
Andrew Hankinson (University of Oxford)
Neil Jefferies (University of Oxford)
Rosalyn Metz (Emory University)
Julian Morley (Stanford University)
Simeon Warner (Cornell University) – presenter
Andrew Woods (LYRASIS)
#WeMissiPRES, online, 2020-09-22/23/24

2. OCFL is …
an open community effort to
define an application-independent
way of storing
versioned digital objects for
long-term digital preservation

3. Origins and Process
• 2017 discussion among digital repository architects about the ideal
layout and characteristics for repository storage (in Oxford)
• Initial community meeting (47 attendees from 32 institutions)
• Collected use cases, best practices, recommendations
• Editorial group, regular community meetings and open process on
github
• Significant design influences from Library of Congress Bagit format
and Stanford University Moab experience (see
https://doi.org/10.3390/publications7020039)

4. 1. Completeness –
so that a repository
can be rebuilt from
the files it stores
• The complete intellectual object is
stored together with its metadata
• Falls in line with standards such as
Trusted Digital Repositories (TDR, ISO
16363), NDSA Levels of Preservation,
and Open Archival Information
Systems (OAIS)
• Allows ease of mapping from one
system to another
These standards typically
talk about what you should
do, but not how
OCFL provides the how

5. 2. Parsability – both
by humans and
machines, to ensure
content can be
understood in the
absence of original
software
• In disaster recovery situations,
humans should be able to
understand the content
• Machine readability allows for
simple applications to be
placed on top of an existing
OCFL storage root

6. 3. Robustness –
against errors,
corruption, and
migration between
storage
technologies
• Strong fixity is baked into OCFL
• Objects can easily be validated
using the inventory.json
file
• Objects can be completely self-
contained

7. 4. Versioning – so
so that a repository
can make changes
objects while
persisting their
history
• Changes to objects are tracked
over time, entire history can be
reconstructed using the
inventory.json file
• Content for a version is
immutable once written
• Forward delta versioning
reduces the amount of content
stored (supports delayed
description workflows)

8. 5. Storage diversity
– to ensure content
can be stored on
diverse storage
infrastructures
including cloud
object stores
• Supports conventional
filesystem metaphor
• Designed to work with various
storage infrastructures
including object stores
prevalent in cloud offerings
(e.g. Amazon S3 API).
• Allows deduplication of
content, lowering overall
storage costs

9. OCFL v1.0
First alpha October 2018
Beta draft June 2019
Version 1.0 July 2020 –
specification and
implementation notes
Validation and manipulation
tools implemented in multiple
programming languages
• Stand alone tools
through
• Fedora 6 using OCFL for
persistence (in development)

10. Specification
Describes:
• OCFL Objects – including the object
structure, versioning, and the
inventory.json which provides a
comprehensive registry of the object
• OCFL Storage Root – how objects are
arranged
with examples to illustrate use
Implementation Notes
Recommendations and practices for
implementing the specification,
including:
• Digital preservation issues – including
rebuildability and fixity
• Storage choices – including different
content cases and infrastructures
• Client behaviors – to support
common operations and objects in
motion

11. Thank you!
Details and links to
get involved:
https://ocfl.io/