Background Aims and Objectives Overall Approach Project partners
Background
Significant properties are those aspects of the digital object which must be preserved over time in order for the digital object to remain accessible and meaningful. The various properties of a digital object may be categorised as content, context (metadata), appearance (eg. layout, colour), behaviour (eg. interaction, functionality), and structure (eg. pagination, sections). Deciding which aspects of each of these categories must be preserved over time is essential to proper preservation planning but is an essential investigation which has not yet been undertaken. There is a critical need to initiate this work in order to establish best practice approaches to preserving digital objects.
The current consensus about digital preservation holds that approaches that are data-centric, ie. concerned about keeping the data object useable over time, offer better prospects for success than those which are process-centric, ie. concerned to keep original software and/or hardware environments operational over time. For a data-centric approach, understanding the significant properties of digital objects is crucial to successfully preserving those objects over time. Process-centric approaches, however, make an underlying assumption that all properties of digital objects are significant and all must be preserved. This assumption needs to be tested and either justified, modified or abandoned.
The fundamental challenge of digital preservation is to preserve the accessibility and authenticity of digital objects over time and domains, and across changing technical environments. This requires acceptance both of the inevitability of change, and of the inherent separation of the logical information object from its physical environment. Any successful preservation strategy must reconcile the requirement to maintain the fixity/integrity of that logical information object, with the inevitable transformation of the technical environment in which the object resides. A useful conceptual model for understanding this is provided by the ‘performance model and the concept of essence’ developed by the National Archives of Australia (NAA) in 2002.
The essence of a performance can be defined in terms of a set of measurable properties, which must be preserved. These properties apply to the logical information object. In addition, the planning and implementation of successful preservation strategies requires a detailed understanding of the properties of the physical object. The most fundamental of these is the representation format in which the information object is encoded, although other explicit and implicit properties also need to be understood. Without an understanding of these ‘representation’ properties, it is impossible to assess the need for preservation action (in terms of risk), or to identify appropriate preservation strategies.
An organisation with curatorial responsibility for digital objects cannot assert or demonstrate the continued authenticity of those objects over time, or across transformation processes, unless it can identify, measure, and declare the specific properties on which that authenticity depends. Nor can it undertake the preservation actions required to maintain access to those objects, unless it can characterise their current technical representations with sufficient detail.
Aims and Objectives
The project will examine the whole concept of significant properties, determine which properties are significant for a range of object types and assess the importance of each of these for future representation of the object, and finally propose a generalised methodology that will enable resource curators to determine the significant properties of classes of digital objects that must be preserved over time. The project will not attempt to define significant properties for high level objects types, such as document like objects. Instead the project will work at a lower level of granularity, focussing on 4 object types initially:
- raster images
- emails
- structured text
- digital audio
These list may be altered or refined during the early phases of the project. The focus of the project will be on the methodologies to be developed for quantifying, comparing and assessing the significant properties of digital objects generally, rather than just on the specific properties of specific object types.
In this way, the project will take forward suggestions regarding the need for further research to support preservation of digital images, relating especially to risk assessment and data loss through migration, made in the recent Digital Image Preservation study undertaken by AHDS for JISC.
In summary the project will:
- expand and articulate the concept of ‘significant properties’
- determine sets of significant properties for a specified group of digital object types
- evaluate methods for measuring these properties for a representative sample of representation formats
- investigate and test the mapping and comparison of these properties between different representation formats
- identify issues which will require further research
Overall Approach
The identification of those properties which are significant to the continued preservation and accessibility of authentic digital objects, across changing technical environments, is a fundamental task for successful digital preservation. Unless such properties can be defined in a rigorous and measurable manner, cultural memory institutions have no objective framework for identifying, implementing, and validating appropriate preservation strategies, nor for asserting the continued authenticity of their digital collections.
In recent years, the need to identify such properties has been highlighted within a number of notable digital preservation programmes. These include the National Archives of Australia, the Electronic Record Archives programme at the National Archives and Records Administration, The National Archives’ Seamless Flow programme in the UK, and the EU-funded DELOS project. Some conceptual work on authenticity and object properties has been undertake as part of the InterPARES 2 project at the University of British Columbia. However, to date, little research has been undertaken on the practical application of the concept and approach. It is therefore widely recognised that there is a pressing need for practical research in this area, to develop a methodology, and begin identifying quantifiable sets of significant properties for specific classes of digital object.
This project will address this need, firstly by locating and investigating all references to ‘significant properties’, ‘significant characteristics’, or ‘essence’ in order to clearly articulate a complete and appropriate working definition of the concept. If necessary, the concept will be developed and expanded to reflect current thinking in digital preservation and to provide a baseline definition for the purposes of the project. Once the concept is properly understood and articulated, the project will examine a range of digital object classes to analyse, assess and specify the significant properties of each class of object. This work will be used as a basis for developing and testing a generic methodology for identifying and measuring significant properties of digital object types. The project will demonstrate the practical application of this methodology to the preservation process, and the effect maintenance of significant properties has on the usability of migrated objects. The project will also examine the application of this methodology to preservation planning, and the validation of preservation actions. It will also identify issues for future research.
Project Partners
Project Lead
Arts & Humanities Data Service (King’s College London)
Project Partner
The National Archives (TNA)
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