Page 32 - Building Digital Libraries

Choosing a Repository Architecture

information can be stored can have an enormous impact on what sys-
tems can be used and where they can be hosted. To go live, the repository
architecture that is selected must support required access controls and
rights management, so it is important to consider these factors early in the
decision-making process.

How Does the Repository Handle Preservation?
A viable preservation strategy is necessary to provide long-term access to
resources. Files and metadata must be protected against corruption or modi-
fication, and measures must be taken to ensure that resources are still usable
through technology transitions. The OAIS model and the TDR checklists
discussed in chapter 1 can be helpful, though possibly overwhelming for
smaller libraries. Chapter 4 discusses preservation in detail.
Table 2.1 depicts a grid developed by the National Digital Stewardship
Alliance that serves as a concise preservation guide and which is useful
when considering repository systems. All things being equal, greater levels
of preservation are better. However, in practical environments, it’s important
to be mindful of the following:

• The purpose of the repository is to make resources usable.
Pres ervation is a tool that promotes use, but it is important
to keep focused on the primary purpose of the repository—
namely, use.
• The repository is the sum total of the people, procedures,
and infrastructure that support it. Needs may be best satis-
fied by a combination of systems, so it is unnecessary to
find a single system that does everything.

• Some resources, especially more complex ones, are difficult
to separate from the platform they are in. It’s desirable to
maintain as few systems as possible, but some resources
may be safer in special-purpose platforms rather than
transferred to a system that may require both objects and
metadata to be restructured or reformatted.
• Preserving resources requires much more than copying files
to tape or online storage. Preserving resources means you
know backups are not corrupted, and you can fully recover
them years later if all hardware and software are lost.
• Even when files can be preserved perfectly, storing
resources in their native format is likely to cause serious
problems in the future unless they are in a widely supported
archival format. Converting files to an archival format
inevitably results in a loss of use or information, and leaving
them in any other format requires emulation or specialized
software for them to be usable. Legal and technical barriers

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