130 · Representative Documents: Format Policies
univerSity of michigan
Sustainable Formats and Conservation Strategies at the BHL
Bentley Historical Library
Digital Curation Services
1150 Beal Avenue
Ann Arbor, MI 48109
11/9/2011 1
Sustainable Formats and Conversion Strategies at the Bentley Historical Library 
November 9, 2011
Version 1.0
Executive Summary 
The Bentley Historical Library is committed to the long‐term preservation of and access to
its digital collections. Because the library must contend with thousands of potential file
formats, Digital Curation Services has adopted a three‐tier approach to facilitate the
preservation and conversion of digital content:
Tier 1: Materials produced in sustainable formats will be maintained in their
original version.
Tier 2: Common "at‐risk" formats will be converted to preservation‐quality file
types to retain important features and functionalities.
Tier 3: All other content will receive basic bit‐level preservation.
This document provides further information on the Bentley Historical Library’s accepted
preservation formats and conversion strategies.
Please see the chart on pp. 3‐5 for a list of sustainable preservation formats and at‐risk
formats that will be subject to conversion.
Tier 1: Preservation of Sustainable Formats 
The library has identified a number of sustainable file formats (pp. 3‐5) that are widely
used and/or nonproprietary, many of which have been recognized as international
standards by bodies such as the International Standards Organization (ISO), ECMA
International, and the Organization for the Advancement of Structured Information
Standards (OASIS). The longevity of these formats has furthermore been acknowledged by
various peer institutions and experts in the digital curation community, including the
Library of Congress’s National Digital Information Infrastructure and Preservation
Digital materials stored in these file formats should remain usable to researchers and
administrative units at the University of Michigan for the foreseeable future and beyond.
The Bentley Historical Library will therefore preserve the original version of content stored
in these sustainable formats at the time of accession. Digital Curation Services will monitor
community best practices and technological advances in case a migration to alternative
preservation formats should prove necessary.
Visit http://fileinfo.com to find basic descriptions of file formats or search the PRONOM
Technical Registry for format specifications and more in‐depth information.
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