Mark Guttenbrunner

Systematic planning for digital preservation: evaluating potential strategies and building preservation plans

A number of approaches have been proposed for the problem of digital preservation, and the number of tools offering solutions is steadily increasing. However, the decision making procedures are still largely ad-hoc actions. Especially, the process of selecting the most suitable preservation action tool as one of the key issues in preservation planning has not been sufficiently standardised in practice. The Open Archival Information Systems (OAIS) model and corresponding criteria catalogues for trustworthy repositories specify requirements that such a process should fulfill, but do not provide concrete guidance. This article describes a systematic approach for evaluating potential alternatives for preservation actions and building thoroughly defined, accountable preservation plans for keeping digital content alive over time. In this approach, preservation planners empirically evaluate potential action components in a controlled environment and select the most suitable one with respect to the particular requirements of a given setting. The method follows a variation of utility analysis to support multi-criteria decision making procedures in digital preservation planning. The selection procedure leads to well-documented, well-argued and transparent decisions that can be reproduced and revisited at a later point of time. We describe the context and foundation of the approach, discuss the definition of a preservation plan and describe the components that we consider necessary to constitute a solid and complete preservation plan. We then describe a repeatable workflow for accountable decision making in preservation planning. We analyse and discuss experiences in applying this workflow in case studies. We further set the approach in relation to the OAIS model and show how it supports criteria for trustworthy repositories. Finally, we present a planning tool supporting the workflow and point out directions for future research.

A Measurement Framework for Evaluating Emulators for Digital Preservation

Accessible emulation is often the method of choice for maintaining digital objects, specifically complex ones such as applications, business processes, or electronic art. However, validating the emulator’s ability to faithfully reproduce the original behavior of digital objects is complicated. This article presents an evaluation framework and a set of tests that allow assessment of the degree to which system emulation preserves original characteristics and thus significant properties of digital artifacts. The original system, hardware, and software properties are described. Identical environment is then recreated via emulation. Automated user input is used to eliminate potential confounders. The properties of a rendered form of the object are then extracted automatically or manually either in a target state, a series of states, or as a continuous stream. The concepts described in this article enable preservation planners to evaluate how emulation affects the behavior of digital objects compared to their behavior in the original environment. We also review how these principles can and should be applied to the evaluation of migration and other preservation strategies as a general principle of evaluating the invocation and faithful rendering of digital objects and systems. The article concludes with design requirements for emulators developed for digital preservation tasks.

Same same but different: comparing rendering environments for interactive digital objects

Digital cultural heritage in interactive form can take different shapes. It can be either in the form of interactive virtual representations of nondigital objects like buildings or nature, but also as born digital materials like interactive art and video games. To preserve these materials for a long term, we need to perform preservation actions on them. To check the validity of these actions, the original and the preserved form have to be compared. While static information like images or text documents can be migrated to new formats, especially digital objects which are interactive have to be preserved using new rendering environments. In this paper we show how the results of rendering an object in different environments can be compared. We present a workflow with three stages that supports the execution of digital objects in a rendering environment, the application of interactive actions in a standardized way to ensure no deviations due to different interactions, and the XCL Layout processor application that extends the characterized screenshots of the rendering results by adding information about significant areas in the screenshot allowing us to compare the rendering results. We present case studies on interactive fiction and a chess program that show that the approach is valid and that the rendering results can be successfully compared.

Migrating Home Computer Audio Waveforms to Digital Objects: A Case Study on Digital Archaeology

Rescuing data from inaccessible or damaged storage media for the purpose of preserving the digital data for the long term is one of the dimensions of digital archaeology. With the current pace of technological development, any system can become obsolete in a matter of years and hence the data stored in a specific storage media might not be accessible anymore due to the unavailability of the system to access the media. In order to preserve digital records residing in such storage media, it is necessary to extract the data stored in those media by some means. One early storage medium for home computers in the 1980s was audio tape. The first home computer systems allowed the use of standard cassette players to record and replay data. Audio cassettes are more durable than old home computers when properly stored. Devices playing this medium (i.e. tape recorders) can be found in working condition or can be repaired, as they are usually made out of standard components. By re-engineering the format of the waveform and the file formats, the data on such media can then be extracted from a digitised audio stream and migrated to a non-obsolete format. In this paper we present a case study on extracting the data stored on an audio tape by an early home computer system, namely the Philips Videopac+ G7400. The original data formats were re-engineered and an application was written to support the migration of the data stored on tapes without using the original system. This eliminates the necessity of keeping an obsolete system alive for enabling access to the data on the storage media meant for this system. Two different methods to interpret the data and eliminate possible errors in the tape were implemented and evaluated on original tapes, which were recorded 20 years ago. Results show that with some error correction methods, parts of the tapes are still readable even without the original system. It also implies that it is easier to build solutions while original systems are still available in a working condition.

Evaluating Emulation and Migration: Birds of a Feather?

Evaluating the results of a digital preservation action, be it migration or emulation, is a complex task. The usual approach for migration is to evaluate object properties after the migration. For emulation strategies the result of the rendering of the object is evaluated. In this paper we argue that the change of object properties when migrating is not sufficient evidence if a digital preservation action is successful or not. Even for migration the rendering process of the digital object is crucial, and as such evaluating object properties is not enough. The difference in evaluation between emulation and migration as a strategy for digital preservation becomes blurred as migration results have to be compared based on the rendering of the target format and the environment used to render the migrated digital object. Evaluation of object properties when migrating will only validate a necessary condition for preserving significant properties, i.e. whether the information underlying a specific property is still present in an object after migration. It cannot guarantee that the rendering based upon the migrated object will exhibit a specific significant property. In this paper we show the view-path of digital objects and explain how emulation and migration actions affect it. We then compare the changes that occur in the view-path and show that these are at least as severe when migrating a digital object as when emulating its rendering environment.

Evaluation of Preserved Scientific Processes

Digital preservation research has seen an increased focus is on objects that are non-deterministic but depend on external events like user input or data from external sources. Among those is the preservation of scientific processes, aiming at reuse of research outputs. Ensuring that the preserved object is equivalent to the original is a key concern, and is traditionally measured by comparing significant properties of the objects. We adapt a framework for comparing emulated versions of a digital object to measure equivalence also in processes.