DDI Specification

DDI has two development lines, described here.


Encompassing all of the DDI-Codebook specification and extending it, DDI-Lifecycle is designed to document and manage data across the entire life cycle, from conceptualization to data publication and analysis and beyond. Based on XML Schemas, DDI-Lifecycle is modular and extensible.

Users new to DDI are encouraged to use this DDI-Lifecycle development line as it incorporates added functionality. Use DDI-Lifecycle if you are interested in:

  • Metadata reuse across the data life cycle
  • Metadata-driven survey design
  • Question banks
  • Complex data, e.g., longitudinal data
  • Detailed geographic information
  • Multiple languages
  • Compliance with other metadata standards like ISO 11179
  • Process management and automation

The current version of the DDI-L Specification is Version 3.1.  DDI 3.1 was published in October 2009, superseding DDI 3.0 (published in April 2008). 


DDI-Codebook is a more light-weight version of the standard, intended primarily to document simple survey data. Originally DTD-based, DDI-C is now available as an XML Schema.

The current version of DDI-C is 2.*.


Older versions of both development lines are available at sourceforge.net. DDI-Lifecycle is versioned as DDI 3.* and DDI-Codebook as DDI 2.*.

Best Practices

Best practices guidelines have been developed for DDI Lifecycle. 


A variety of tools have been developed or are under development for working with DDI. Please see Tools section under the DDI Resources tab.