Table of Contents

1. Introduction

1.1 Version

1.2 Definitions and Terminology

2. Archival Reel Format

2.1 Reel Structure

3. Archival File System

3.1 Logical Frame Format

3.2 Control Frame

3.3 Visual Table of Content

3.4 Representation Information

3.5 Digital Table of Content

3.6 Digital Content

3.7 Visual Content

4. References

Appendix A – Control Frame Format

Appendix B – Boxing Format

Appendix C – Table of Content Format

1. Introduction

The purpose of this document is to define a generic preservation reel structure, that organizes digital and visual data on an Optical Storage Medium (OSM) based on photo-sensitive, micrographic film. This document describes both the physical and logical reel structure. The goal of the structure is to ensure that the stored data remains complete and accessible in the long-term; spanning several centuries. The structure is therefore designed to be self-contained, all the information needed to safely store, maintain and read back the information in the future is kept on the reel itself.

The physical reel structure is called Archival Reel Format (ARF) and the logical reel structure is called Archival File System (AFS). Both formats derive from several key properties of the storage medium:

• Micrographic film is a long-term stable medium (several hundred years in ideal conditions); no periodical migration of the stored data is necessary for long-term archiving.
• Micrographic film can store two types of data: Non-digital data (analogue, visual or human-readable content) and digital data (machine-readable content), as well as a combination of both (hybrid content).
• Micrographic film can only be written once, and read many times (true WORM technology); it is not possible to alter the data stored in the film later.
• Micrographic film can be read (retrieval of the stored data) independently of the technology used to record the data.
• Micrographic film is a sequential access medium.
• Both ARF and AFS are simplified formats designed for a non-erasable WORM medium that fulfills the above properties.

1.1 Version

The version number for ARF and AFS is in the form M.m.r, where M, m and r are natural numbers. With this three-numbered versioning it is possible to track the different revisions of the ARF and AFS specifications as well as the nature of the changes. The three components of the version number are updated as follows:  • M: It is incremented when a major update has been made to the ARF or AFS specifications. A major update is a change to the specification semantics that is expected to break compatibility with older versions.  • m: It is incremented when a minor update has been made to the ARF or AFS specifications. A minor update is a change to the specification semantics that is not expected to break compatibility with older versions (with the same M value).  • r: It is incremented when a revision has been made to the ARF or AFS specifications. A revision is a change to the specification to improve the clarity of the format, without modifying its semantics.