Digital preservation glossary
| Term | Definition |
|---|---|
| 3D assets | Digital files that represent objects or elements in three-dimensional space. These assets can comprise multiple attributes and/or separate files and are generally created using 3D modelling or scanning software. 3D assets are used in media and games production, product design and architecture and to create immersive experiences. They can also be used to capture representations of real-world objects, historical artifacts and places. Some common file formats for 3D assets include OBJ, FBX, STL, and AMF (Adobe, n.d.). |
| Access copy | "Also called distribution or reference copy. An access copy provides easy access or review of content compared to the less accessible preservation or intermediate copy. The access copy is usually low resolution and made available online. An access copy should be a widely supported format that is easy to playback" (National Archives and Records Administration [NARA], 2023). |
| Bit rot | Bit rot, also known as data rot, data decay and bit decay, refers to the deterioration of data stored on storage media. The primary cause of bit rot is physical degradation of storage devices. Bit rot causes corruption of data, which can affect its accessibility and usability (Awati, 2024). |
| Checksums | Checksums, or hashes, are unique alphanumeric values or “digital fingerprints” that represent the bitstream of an individual computer file or set of files. Checksums are used to support fixity checking. They are typically applied to digital materials stored within a repository and can also be used before and after transfers or migrations to determine whether files have maintained the same value and have not changed during the process. MD5, SHA-256, and SHA-512 are some commonly used algorithms for generating checksums (Digital Preservation Coalition [DPC], 2015). |
| Digital materials | Data, records, collection objects and outputs in electronic form including text, images, audio, moving images, 3D assets, and immersive media, that can be accessed by a computer. They can be born digital (created digitally), or digitised (physical and analogue materials which are converted into digital files). |
| Digital preservation | The coordinated, ongoing set of processes and activities that maintains digital materials in understandable, accessible and usable forms for long term use by user communities, beyond the limits of technological or organisational failure or change. The level of digital preservation reasonably attainable for digital materials varies based on factors such as format, complexity and available technology (DPC, 2015). |
| Digital repository | Infrastructure including applications and systems, designed to store, manage, re-use and curate digital materials. |
| Emulation | A means of overcoming technological obsolescence of hardware and software by developing techniques for imitating obsolete systems on future generations of computers. This technique attempts to preserve the original behaviours and the look and feel of applications, as well as informational content (DPC, 2015; National Archives of Australia [NAA], 2020). |
| File compression | File compression refers to reducing the size of a digital file and/or changing its attributes , such as resolution, dimensions or bit depth. Compression can be lossy or lossless (Awati, 2021). See lossy compression and lossless compression. |
| Fixity checking | Also known as integrity checking. A method for ensuring the integrity of a file and verifying it has not been altered or corrupted. It is most often accomplished by using checksums (NAA, 2020). See the Fixity checking guide for further information. |
| Format migration | A means of overcoming technological obsolescence by transferring digital files from one hardware/software generation to the next (NAA, 2020). |
| Immersive media | Digital technology that creates or enhances an environment, either to simulate the physical world or to create something completely new. It uses methods such as reality (VR), augmented reality (AR), and mixed reality (MR) (Interaction Design Foundation, 2024). |
| Integrity checking | See fixity checking. |
| Lossless compression | Lossless compression restores and remakes file data in its original form after the file is decompressed. Hence, when a file is compressed, the quality remains the same. This form of compression is reversible (Awati, 2021). |
| Lossy compression | Lossy compression reduces the size of a file by permanently removing less important information from the file. This type of compression is irreversible. (Awati, 2021). It is not recommended for preservation master files. But can be a useful method to use for making digital materials more easily accessible. Common examples of lossy file types include JPEG (for images), MP3 (for audio), and MPEG (for video). See access copy. |
| Normalisation | The process of transforming a digital record from one data format (typically proprietary) to an archival data format (usually an open standard) (NAA, 2020). |
| Preservation master | The preservation master, or preservation copy, is the most original copy and/or high quality duplicate of the original record (NARA, 2023). Preservation masters are produced when original records are at risk for loss of information, typically deterioration or obsolescence. Preservation master files are created at high to maximum capture specifications and can therefore serve a variety of purposes, including satisfying long-term preservation needs, as well as fulfilling client requests for high-quality files (NAA, 2020). |
References
Adobe. (n.d.). A guide to 3D file types. https://www.adobe.com/products/substance3d/discover/3d-files-formats.html
Awati, R. (2024, Jul 25). What is bit rot? TechTarget. https://www.techtarget.com/searchstorage/definition/bit-rot
Awati, R. (2021, Oct 11). Lossless and lossy compression. TechTarget. https://www.techtarget.com/whatis/definition/lossless-and-lossy-compression
Digital Preservation Coalition. (2015). Digital Preservation Handbook, (2nd ed.). https://www.dpconline.org/handbook
Interaction Design Foundation. (2024). Immersive media. https://www.interaction-design.org/literature/topics/immersive-media
National Archives and Records Administration. (2023). Archival formats: Glossary of terms. https://www.archives.gov/preservation/formats/glossary.html
National Archives of Australia. (2020). Digital Preservation Policy, https://www.naa.gov.au/about-us/who-we-are/accountability-and-reporting/archival-policy-and-planning/digital-preservation-policy