All active versions of DDI available for download.
Controlled vocabularies play a critical role in metadata standards in terms of (1) semantics -- definition of the meaning of metadata elements, and (2) content -- declaration of instructions for what and how values should be assigned to elements.
Work is under way on three RDF vocabularies, the DDI-RDF Discovery vocabulary for publishing metadata about datasets into the Web of Linked Data, PHDD, an vocabulary for describing existing data in rectangular format, and XKOS, an RDF vocabulary for describing statistical classifications, which is an extension of the popular SKOS vocabulary.
In constructing DDI special care was taken to review related standards as well as previous versions of DDI in order to provide clear mapping to the contents of outside standards or to incorporate content where appropriate. Over 25 standards were evaluated.
The DDI Registry enables you to obtain an agency ID from the DDI Alliance. Using this permanent identifier in your DDI instances allows you to specify the authoritative source of your data and metadata. The registry is connected with the global DNS system, allowing DDI URNs to be resolved using standard tools. The source code for the registry and several related tools is also available under an Open Source license from the web site. The DDI Registry is maintained by the DDI Alliance.