Digital Preservation

1. Introduction to Digital Preservation

Digital preservation is an essential process for ensuring the long-term survival, accessibility and usability of information stored in digital form. In the modern information environment, a substantial amount of knowledge is created, communicated and stored through computers and other digital technologies. Electronic books, research articles, digital photographs, audio recordings, videos, databases, websites and electronic records are important sources of information that may need to remain accessible for many years.
Unlike printed materials, digital resources depend on hardware, software, file formats and storage technologies for their accessibility. These technologies change continuously, and digital information may become inaccessible even when its original files still exist. For example, a document created using outdated software may not open correctly in a modern application. Similarly, information stored on an old floppy disk may become inaccessible because compatible reading devices are no longer commonly available.
Digital preservation addresses these problems through systematic planning, appropriate technologies and continuous management. It involves more than simply saving digital files. Its purpose is to maintain the information, integrity, authenticity and usability of digital resources despite technological changes and other risks.
Meaning of Digital Preservation
Digital preservation refers to the systematic management and protection of digital information to ensure that it remains accessible, understandable and usable over time. It includes activities such as maintaining secure copies, monitoring file integrity, documenting digital resources, managing technological changes and converting files into suitable formats when necessary.
Definition of Digital Preservation
According to the Digital Preservation Coalition (DPC), digital preservation refers to: "The series of managed activities necessary to ensure continued access to digital materials for as long as necessary".
This definition emphasises three essential aspects:

1. Managed activities: Digital preservation requires organised and planned actions rather than occasional or accidental efforts.
2. Continued access: Digital resources must remain accessible and usable despite changes in technology.
3. Long-term responsibility: Preservation activities must continue throughout the period for which the information needs to be retained.

Thus, digital preservation is a continuous process rather than a one-time activity.

2. Nature and Scope of Digital Preservation

Digital preservation covers a wide variety of digital information resources and the technologies required to maintain them. Its scope extends beyond protecting physical storage devices to preserving the content, structure, context and functionality of digital information.
Born-Digital Materials
Born-digital materials are resources originally created in digital form. Examples include electronic documents, emails, digital photographs, research datasets, electronic journals, websites and software applications. Since these materials may never have existed in physical form, their preservation depends upon maintaining suitable digital environments and ensuring that the information can be interpreted in the future.
Digitised Materials
Digitised materials are digital representations of resources originally available in physical or analogue form. These include scanned manuscripts, digitised books, historical photographs and audio recordings converted from analogue media. For example, a printed manuscript may be scanned to create digital image files. Digital preservation ensures that these files remain accessible and usable over time. However, preservation of the digital copies does not eliminate the need to protect the original physical manuscript.
Bit-Level Preservation
Bit-level preservation focuses on maintaining the exact sequence of binary digits, known as bits, that constitute a digital file. Its purpose is to prevent accidental changes, corruption or loss of stored information. Maintaining multiple copies, checking file integrity and replacing unreliable storage media are important activities. However, maintaining the original bits does not necessarily guarantee that the information will remain understandable or usable.
Logical Preservation
Logical preservation focuses on ensuring that digital information can continue to be interpreted and used. It addresses the dependence of digital files on particular software applications, file formats and computing environments. For example, preserving an old electronic document requires not only retaining its data but also ensuring that appropriate software can display its content correctly. Therefore, effective digital preservation must address both the physical integrity of digital data and its continued interpretation and use.

3. Need and Importance of Digital Preservation

Digital preservation has become increasingly important because digital information is vulnerable to several technological, organisational and environmental risks.

1. Protection Against Data Loss: Digital information can be lost because of hardware failure, accidental deletion, storage corruption, natural disasters or cyberattacks. Digital preservation reduces the risk of permanent information loss through controlled storage, multiple copies, integrity verification and recovery procedures.
2. Prevention of Technological Obsolescence: Technological obsolescence occurs when hardware, software or file formats become outdated and are no longer supported by available technologies. For example, older multimedia files may require applications that are no longer maintained. Digital preservation provides strategies for maintaining accessibility despite these changes.
3. Long-Term Accessibility of Information: Digital resources may be required for academic, administrative, legal, historical or research purposes long after their creation. Preservation ensures that valuable information remains available to present and future users.
4. Maintenance of Authenticity and Integrity: Digital files can be modified, intentionally or accidentally, without producing visible evidence of alteration. Digital preservation establishes procedures to verify the integrity of resources and maintain evidence of their origin, history and authenticity.
5. Protection of Cultural and Intellectual Heritage: Historical documents, cultural records, scientific publications and other valuable materials increasingly exist in digital form. The UNESCO Charter on the Preservation of Digital Heritage (2003) recognises the importance of safeguarding digital heritage for future generations. Digital preservation helps protect this intellectual and cultural record.
6. Support for Research and Education: Research datasets, scholarly publications, institutional records and electronic learning materials may retain value long after their initial use. Digital preservation supports their future discovery, verification, consultation and reuse.
7. Institutional Continuity and Accountability: Organisations depend on digital records for administration, decision-making and accountability. Maintaining these records over their required retention periods supports institutional continuity and provides evidence of past activities and decisions.

In this way, digital preservation protects not only digital files but also the knowledge, evidence and institutional memory represented by those files.

4. Fundamental Principles of Digital Preservation

Effective digital preservation is guided by several principles that help institutions maintain reliable digital information over extended periods.

• Authenticity: Authenticity refers to the assurance that a digital resource is what it claims to be and that its identity and origin can be established. A digital document should retain sufficient evidence of its creator, provenance and subsequent management. Provenance refers to the origin, ownership and history of a resource. Maintaining authenticity requires reliable documentation, controlled procedures and records of significant changes made to digital materials.
• Integrity: Integrity refers to the completeness and accuracy of digital information. It ensures that data have not been altered, corrupted or lost without detection. Integrity can be monitored through techniques such as checksums, which produce a calculated value from the contents of a digital file. Comparing checksum values over time helps identify unexpected changes.
• Accessibility and Usability: Accessibility means that authorised users can retrieve digital information when required. Usability means that the retrieved information can be interpreted and used meaningfully. A file may remain accessible in storage but become unusable because suitable software is unavailable. Digital preservation must therefore address both conditions.
• Reliability and Security: Digital preservation systems should protect resources against unauthorised modification, accidental deletion, malicious activity and technical failure. Security measures include controlled access permissions, monitoring, secure storage and documented recovery arrangements.
• Sustainability: Sustainability refers to the ability to maintain preservation activities over time through appropriate financial, technical and organisational resources. A preservation programme must consider continuing costs, technological changes, staff expertise and institutional responsibilities. The objective is not simply to purchase storage equipment but to maintain a reliable preservation service.
• Documentation and Accountability: Preservation activities should be documented so that future custodians can understand how digital resources were acquired, managed, modified and maintained. Documentation supports transparency, accountability and informed decisions about future preservation actions.

5. Digital Preservation Strategies

Digital preservation strategies are the technical and organisational approaches used to protect digital resources from deterioration, technological obsolescence and loss of accessibility. No single strategy is suitable for every type of digital resource. The appropriate approach depends on the nature of the material, its significant characteristics, the available technologies and the requirements of future users.

1. Refreshing: Refreshing involves copying digital information from existing storage media to new media of the same or a similar type before the original storage becomes unreliable. For example, information stored on an ageing hard disk may be copied to a new hard disk to reduce the risk of hardware-related data loss. Refreshing protects information against storage media deterioration. However, it does not resolve problems associated with obsolete file formats or software applications.
2. Replication: Replication involves creating and maintaining multiple copies of digital information in different storage systems or locations. For example, an organisation may retain one copy of its digital records on local storage and another in a geographically separate storage facility. Replication reduces the possibility of permanent loss from the failure of a single device or location. Nevertheless, replicated copies must be monitored carefully because damaged or incorrectly modified files may otherwise be copied to other locations.
3. Migration: Migration is an important digital preservation strategy that involves transferring digital information to a new technical environment or converting it into a more suitable file format.Two common forms are:
   • Storage media migration: Transferring digital information from one storage technology to another, such as moving files from older magnetic media to a modern storage system.
   • File format migration: Converting information from an older file format into a format that can be supported by current and future software.
   For example, an old word-processing document may be converted into a more sustainable document format to maintain its readability. Migration is widely used because it allows digital information to remain compatible with changing technologies. However, conversion may affect formatting, structure, embedded information or other characteristics of the original file. Therefore, migration should be tested, documented and evaluated to ensure that important information is not lost.
4. Emulation: Emulation involves recreating the behaviour of an older computer system or software environment using modern technology. An emulator is a program that enables a newer computing system to imitate the functions of an earlier system. For example, an old educational computer application may require a particular operating system that is no longer commonly available. An emulator may reproduce the required environment and allow the application to function without converting its original files. Emulation is particularly useful for complex digital resources such as interactive multimedia, computer games and software applications. Its limitations include technical complexity, software licensing restrictions and the continuing need to maintain suitable emulation environments.
5. Normalisation: Normalisation involves converting digital files into selected, standardised formats, usually during their acquisition or entry into a preservation system. For example, an institution receiving documents in several formats may create standardised preservation copies in an approved format. Normalisation simplifies the management of diverse digital collections and can reduce dependence on numerous software applications. However, the conversion process may change certain characteristics of the original resources. Therefore, institutions generally need to evaluate the converted files and retain original files when appropriate.
6. Encapsulation: Encapsulation involves organising a digital resource together with the information needed to understand, manage and interpret it. This may include technical metadata, file format specifications, software requirements, documentation and information about relationships between files. For example, a research dataset may be preserved along with its data dictionary, methodology, coding instructions and software documentation. Encapsulation improves the possibility of interpreting digital resources in the future, although it does not independently resolve every problem of technological obsolescence. Comparison of Major Digital Preservation Strategies