Data Documentation Initiative (DDI)
The DDI is a metadata description standard closely linked with and complementing SDMX. The original DDI version (also called DDI codebook) focused on documenting censuses and surveys with the view of archiving and preserving the statistical information. A newer version, DDI 3.0 (all called DDI lifecycle) also describes metadata as they are created and used throughout the statistical production process.
Documentation and support
The Data Documentation Initiative (DDI): An Introduction for National Statistical Institutes
This paper introduces DDI to those coming from national statistics institutes (NSIs). DDI was conceived as metadata documentation for the social and behavioural sciences and it is maintained by the DDI Alliance. It has two major development lines: the original DDI and the lifecycle-based DDI. The former includes the same information as a traditional codebook, describing variables and codes, while the latter, which is also multilingual, focuses on describing metadata as they are created and used throughout the data production lifecycle. The relationships with other standards are also analysed. In particular, DDI can possibly be related to a more general statistical framework with the GSBPM being the centre-piece of such framework.