The BagIt specification is a hierarchical file packaging format for the creation of standardised digital containers called 'bags,' which are used for storing and transferring digital content. Derived from work by the Library of Congress and the California Digital Library, a bag consists of a ‘payload’ - the digital content - and ‘tags' - metadata files to document the storage and transfer of the bag. There are a number of Bagit-specific tools to ease bag creation, including the BagIt Library, a Java-based software library to support the creation, manipulation, and validation of bags. For those less comfortable with command-line interface, the Bagger application provides a graphical user interface to the BagIt Library.
The United States Library of Congress, and the National Digital Information Infrastructure and Preservation Program (NDIIPP)
Licensing and cost
BSD License - free. The BagIt Library is public domain.
Bagger 2.1.2 was released in February 2012. BagIt Library 4.1 was released in January 2012. The Library of Congress website implies ongoing development of the Transfer Utilities.
Platform and interoperability
Both the BagIt Library and Bagger require Java 6.
Bags contain at minimum three elements: a ‘payload’ and at least two ‘tags.’ The payload consists of the content being preserved. The first tag is a manifest itemising the files making up the content along with their checksums; the second is a bagit.txt file identifying the container as a bag and giving the version of the specification used and the character encoding of the tags. The specification additionally allows for several optional tags.
Documentation and user support
Documentation is extremely sparse, primarily consisting of README files detailing release notes. The BagIt specification itself can be found through the Library of Congress website. It appears that the main user support consists of a mailing list hosted by Sourceforge; however, the list archive only shows 11 posts for 2011.
The BagIt Library uses a command-line interface, while Bagger provides a graphical user interface. No installation is required; the tools can simply be downloaded and run, although it may not be immediately clear to users how to do so.
BagIt is designed to create a common language for users exchanging digital materials, essentially negating the need for expertise about others’ protocols. However, for configuration, familiarity with one’s own repository’s technical protocols is essential.
The BagIt specification is an Internet Engineering Task Force (IETF) internet draft.
Influence and take-up
The BagIt specification has become widely accepted in the preservation community, and is used by the Library of Congress, Chronopolis, and The Stanford Digital Repository, among others. The Transfer Utilities have been downloaded nearly 4000 times from Sourceforge.
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