DDI Versions — DDI 4.0 dev documentation

# DDI Versions

Published versions of DDI

Version | Year published | Documentation link
--- | --- | ---
2.1 | 2003 | http://www.ddialliance.org/Specification/DDI-Codebook/2.1/DTD/Documentation/DDI2-1-tree.html
2.5 | 2012 | http://www.ddialliance.org/Specification/DDI-Codebook/2.5/XMLSchema/field_level_documentation.html
3.0 | 2008 | http://www.ddialliance.org/Specification/DDI-Lifecycle/3.0/XMLSchema/Documentation/
3.1 | 2009 | http://www.ddialliance.org/Specification/DDI-Lifecycle/3.1/XMLSchema/FieldLevelDocumentation/
3.2 | 2012 | http://www.ddialliance.org/Specification/DDI-Lifecycle/3.2/XMLSchema/FieldLevelDocumentation/