Structured, descriptive documentation of the content, meaning, provenance, and access for a single data set. Originally developed as an XML DTD, Codebook retains the hierarchical structure of a DTD in describing the contents of a descriptive codebook for a data set including: identification, authorship, ownership, purpose, background methodologies, source information, provenance, quality control, access, physical file structures, variables/variable groupings, and related materials. Extensive information is found within the variable description covering the data source, derivation activity, representation, data typing, variable role, and restrictions.

Supports Activities:

• Descriptive documentation of the content, meaning, provenance, and access for a single data set
• Archival preservation of descriptive content
• Input basis for more complex descriptions
• Input content for discovery and exchange of data at the study, data file, variable, and question level
• Input content for a structured human-readable codebook for the data set as a whole
• Populate variable and question banks to explore available data and question structures for reuse in new surveys

Version 2.5 [current version]

Publication date: 20120-1-17 Update: 2014-01-29

• DOWNLOAD LINK
• XML Schema files (namespace) http://www.ddialliance.org/Specification/DDI-Codebook/2.5/XMLSchema/
• XML DTD

Additions in version 2.5: This version is an XML Schema. It incorporates new substantive elements requested by the community to better support use in statistical agencies and is designed to make it easier to migrate documents to DDI Lifecycle for those interested in doing so. 
DDI Codebook Version 2.5 was modified on January 29, 2014. This is a sub-minor version change (version 2.5.1) which DOES NOT change the namespace of DDI-C. Modifications corrected an omission of DataFingerprint from 2.5, relaxed cardinality to support multiple languages, and expanded the documentation

Version 2.1

Publication date: 2003-03-26

• DOWNLOAD LINK
• XML Schema (namespace) https://ddialliance.org/Specification/DDI-Codebook/2.1/XMLSchema/Version...
• XML DTD

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. 

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.