The rapid ongoing changes in software and hardware put digital information at risk. The challenge is to keep electronic data accessible, viewable, and usable for the future when the original software to interpret them has become unavailable. Digital preservation has thus turned into on of the most pressing challenges not only within the digital library community, but also in other areas such as archives and data centres. This chapter introduces the concepts and challenges in the field of digital preservation including the OAIS reference model. We give an overview about the projects and initiatives worldwide dealing with this challenge. We furthermore present preservation planning as a key concept at the heart of preservation endeavours in detail.
The Current State Of Research
The companion document to the UNESCO charter for the preservation of the digital heritage (UNESCO, 2003a) provides a good overview of preservation strategies. Research on technical preservation issues is focused on two dominant strategies—migration and emulation. Migration requires the repeated copy or conversion of digital objects from one technology to a more stable or current, be it hardware or software. Each migration incurs certain risks and preserves only a certain fraction of the characteristics of a digital object. The Council of Library and Information Resources (CLIR) published different kinds of risks for a migration project (Lawrence, Kehoe, Rieger, & Walters, 2000).
Emulation as the second important strategy is a means of overcoming technological obsolescence of hardware and software by developing techniques for imitating obsolete systems on future generations of computers (Jones & Beagrie, 2002). Jeff Rothenberg (Rothenberg, 1999) envisions a framework of an ideal preservation surrounding. The Universal Virtual Computer (UVC) concept (Van der Hoeven, Van der Diessen, & Van En Meer, 2005) uses elements of both migration and emulation, allowing digital objects to be reconstructed in their original appearance. The UVC is independent of any existing hardware or software, it simulates a basic architecture including memory, register and rules. An emerging approach of emulation is modular emulation. Jeffrey van der Hoeven presented the modular emulator called Dioscuri in (Van der Hoeven & Wijngaarden, 2005). It imitates the hardware environment by emulating the components of the hardware architecture. Each hardware components is run as individual emulators and the components are assembled in order to create a full emulation process.
Key Terms in this Chapter
Digital Preservation: The series of managed activities necessary to ensure continued access to digital materials for as long as necessary. It refers to all of the actions required to maintain access to digital materials, both digitised and born digitally, beyond the limits of media failure or technological change (Jones & Beagrie, 2002).
Digital Object: An object composed of a set of bit sequences ((CCSDS), 2002).
Preservation Planning: The process of defining a procedure for preserving a given collection of digital objects. The plan treats organisational, technical and financial aspects of the specific preservation problem at hand.
Emulation: A means of overcoming technological obsolescence of hardware and software by developing techniques for imitating obsolete systems on future generations of computers (Jones & Beagrie, 2002).
OAIS: Model Reference Model for an Open Archival Information System ((CCSDS), 2002).
Migration: A means of overcoming technological obsolescence by transferring digital resources from one hardware/software generation to the next (Jones & Beagrie, 2002).
Archive or Repository: An organization that intends to preserve information for access and use by a designated community ((CCSDS), 2002).