DDI Codebook 2.1

DDI Codebook 2.1 Development History

DDI Codebook was the first version of the DDI to be published (Version 1 was released in 2000). DDI 2.0 was released in 2003, with Version 2.1 following two years later. Version 2.* added coverage of aggregate data and geography.

The canonical expression of DDI 1.* through 2.1 is a Document Type Definition (DTD), although XML Schema versions have been created.The DTD can be converted to a schema using XML software, but the DTD should be used as the authoritative source for instance creation and validation. The legacy schema are preserved on the DDI site, but they are not kept in sync with DTDs prior to DDI 2.5.

A new version in the DDI Codebook line -- 2.5 -- was published on January 29, 2014. This version is an XML Schema. It incorporates new substantive elements requested by the community and is designed to make it easier to migrate documents to DDI Lifecycle for those interested in doing so.

This page contains links to the codebook DTD, its structure, and other information on how it can be used. Archival DTDs and Schema can be found in the SourceForge.net CVS repository by following any of the "Download" links below. 

Document Type Definition (DTD)

XML Schema (XSD)

DDI Lite (Recommended Elements)

Version Control for DTD

Information on the DTD Elements

This information is provided as instruction and support for those using the DTD or exploring its use in their markup efforts. Users should note that the Tag Library is an evolving document, and additional remarks, definitions, and examples will be added periodically.

The DDI Committee encourages researchers to use and evaluate the Tag Library and to send comments on their experiences to ddi@icpsr.umich.edu.


For questions, please contact the DDI Secretariat