The DDI Technical Committee is happy to announce the availability of the public review of DDI Lifecycle 4.0.

DDI Lifecycle 4.0 introduces a model-based approach to DDI Lifecycle. A common information model provides the foundation for its XML, JSON, RDF, and UML representations, allowing the same metadata to be expressed across different technical environments. The intention is to preserve the substantive content and meaning of DDI Lifecycle 3.3, rather than introduce a wholesale redesign. The metadata content of DDI 3.3 has been converted into the new 4.0 model.

The public review will run for six weeks, comments are requested by December 6th 2026.

Users can provide questions and comments to the TC using GitHub issues with a free GitHub account at:
https://github.com/ddialliance/ddimodel/issues

If you want to submit comments but don't want to use GitHub, please use this Comment Submission Form.

The public review package is available at:
https://github.com/ddialliance/ddimodel/releases

Webinar for voters and reviewers

The Technical Committee will host a webinar at the start of the voting period to:

• Explain the purpose and scope of DDI Lifecycle Version 4.0
• Highlight key changes
• Answer questions from reviewers and voters

Documentation and Automation

The documentation for DDI Lifecycle 4.0 is also auto-generated in real time from the model, and can be viewed in light or dark mode at:
https://docs.ddialliance.org/DDI-Lifecycle/dev/model/

The latest DDI Lifecycle development outputs are auto-generated and can be viewed at:
https://docs.ddialliance.org/DDI-Lifecycle/dev/output/

Changes from DDI 3.3

Alongside this change in approach, several targeted, backward-compatible additions extend the model. A new Population item type supports alignment with DDI Common Core, ISO/PAS 25955, by describing a population in relation to its defining universe and its geographic and temporal scope. CodeValue updates allow controlled-vocabulary terms to be identified directly through instance URIs and explicitly associated with DDI CodeLists. Additional managed representations provide reusable, identifiable definitions for domains where these were previously unavailable.

The multilingual string structures used in DDI Lifecycle 3.3 have also been simplified. The revised approach represents language-tagged text more directly in the supported serialization formats, particularly RDF, which natively supports language-tagged strings through rdf:langString A complete list of changes can be found in the attached changelog report.

Review Package

The ddi-lifecycle-4.0-PR.zip package includes:

• lifecycle40.xsd - XML Schema 1.0
• lifecycle40.schema.json - JSON Schema 2020-12
• lifecycle40.ttl - OWL ontology in W3C Turtle
• lifecycle40.ontology.jsonld - OWL ontology in JSON-LD
• lifecycle40.context.jsonld - JSON-LD context for RDF instances
• lifecycle40.shacl.ttl - SHACL Core/SPARQL
• lifecycle40.shacl12.ttl - SHACL Core/SPARQL 1.2
• lifecycle40.dctap.csv - Dublin Core Tabular Application Profile
• lifecycle40.xmi - OMG's UML XMI 2.5

Also available online at https://docs.ddialliance.org/DDI-Lifecycle/dev/output/

Example instances for XML, JSON, and RDF in JSON-LD are in ddi-lifecycle-4.0-PR-example-instances.zip.

Other formats and languages

Other formats and programming language implementations are also available but are not included in the review package. Prebuilt packages are available in the ddi-lifecycle-all-outputs workflow outputs under Actions.

• Typescript / Javascript
• Python dataclass / Python Pydantic v2
• csharp
• LinkML
• GraphQL schema language
• Graphviz/DOT (light and dark mode)
• Sphinx documentation (light and dark mode)

Changelog since beta 4:
Full Changelog: v4.0-beta.4...v4.0-pr

If you have questions, please contact the Technical Committee [tc@ddialliance.org].