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 guidelines have been developed for DDI Lifecycle.