Sustainability Assessments at the British Library: Formats, Frameworks, & Findings

File format assessments have been the subject of much debate in and outside of the preservation community in the past decade. Recognizing the unique structural, operational, and collecting context of the British Library, the Library’s digital preservation team recently initiated new format assessment work to deliver recommendations on which file formats will best enable the preservation of integral, authentic representations of British Library collection content over the long term. This paper describes the work carried out to review previous assessments, identify appropriate sustainability categories and newly assess formats accordingly. We posit that the relatively ‘fuzzy’ nature of a file format requires a relatively open-ended assessment framework and a nuanced understanding of preservation risk that does not solely lie with ‘all-or-nothing’ format obsolescence. We review other work in this area and suggest that whilst previous format assessment work has addressed a range of subtly different aims, experience has since indicated that some of the criteria used such as considering number of pages in a format specification as a measure of complexity may be invalid. British Library assessments are made on documented points of principle, for example, an emphasis on evidence-based preservation risks and the avoidance of numerical scores leading to comparisons between formats, and these have formed the base upon which sustainability categories are defined. We present these categories, which help to identify preservation risks or other challenges in the management of digital collections, and provide an overview of initial assessments of three formats: TIFF, JP2, and PDF. We acknowledge however, that implementation of preservation requirements, e.g., the use of particular preservation-justified file formats, must be balanced against other business requirements, such as storage costs and access needs, and argue that transparency of this format assessment process is fundamental if the resulting recommendations are to be fully understood in the future.