TRAC, nestor's Catalogue of Criteria for Trusted Digital Repositories and DRAMBORA were each developed within a culture of cooperation, and can consequently be used in association with one another to facilitate repository assessment. The diagram below indicates one of the ways in which they are used together.

The timeline across the bottom of the figure illustrates the value of these tools at every stage of the digital repository lifecycle.

Irrespective of whether repositories are in planning, development or production stages, they can benefit from the exposure of systems, policies, procedures and infrastructures to one or more of these assessment mechanisms.

Self assessment is indicated in the yellow box, and is analogous to repository management. DRAMBORA's methodology represents the softer approach to audit; many parts of its methodology are intended to be almost indistinguishable from good management practice.

During the self assessment process repositories are expected to define and refine repository policy, aggregate and where necessary create documentation and evidence capable of demonstrating conformance with these policies and evaluating and responding to perceived shortcomings, which manifest themselves in terms of risks.

During formal audit (which may be undertaken as part of a certification process, depicted within the red box) a similar approach is adopted, albeit from the perspective of an individual actor. Again, policies are analysed, available evidence is evaluated and a judgement is issued relating to the extent that the repository conforms to available metrics.

In order to facilitate these audit methodologies, the objective metrics presented within TRAC and nestor's Catalogue of Criteria are pervasive influences, presenting structured insights into the kinds of issues that may correspond to risks, shortcomings and perceived points of failure.

They represent a constant, objective and globally defined set of characteristics that repositories should strive for and see realised through each iteration of self assessment and external audit.

When combined, these tools offer a flexible methodology that supports an organisation or auditor in determining conformance to objective and rigorously defined metrics.