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The suite of DDI Alliance products has been formally recognized as an international standard through the publication of ISO/PAS 25955:2026 -- Learn more
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DDI-Lifecycle (DDI-L)

XML Schema (entry point): https://ddialliance.org/Specification/DDI-Lifecycle/3.3/XMLSchema/instance.xsd
Current Field Level Documentation

Supports Activities

  • Descriptive documentation of the content, meaning, provenance, and access for a single data set or series
  • Archival preservation of descriptive and production content
  • Metadata driven statistical systems
  • 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
  • Metadata reuse for quality control and consistency
  • Reuse of metadata within and between studies
  • Defining intended processes for data capture, processing, preservation, and access
  • Management of single or multi-model data capture including generation of data capture forms and instrument content

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DDI-Lifecycle expands on the idea of DDI-Codebook in terms of content coverage, depth, metadata management over time, reusable metadata, and support for the planning, capture, processing, storage, discovery and dissemination of research data. DDI-Lifecycle is the most comprehensive of the DDI products covering conceptual and methodological objects, processing, quantitative and qualitative data objects, and data management. DDI-Lifecycle is appropriate for longitudinal, linked, and other complex datasets.

Support for the DDI Data Lifecycle from planning through analysis. Organized around major areas of activity: Conceptual Content, Study Unit, Data Collection, Logical Records, Physical Records, Physical Instances (data store), Archiving, Groups, Resources, and Comparison. Introduces the idea of metadata reuse within and between studies, support for repeated surveys, creation and management of questionnaires, and management of metadata over time. Content may be used to populate question, variable, and concept repositories.