Major Components of the DDI Model

1. Major Components of the DDI Model • Document Description • Study Description • File Description • Data Description • Related Material

2. DDI Structural Diagram

3. Section 1: Document Description • Citation– Bibliographic information describing the marked-up document. • Guide – Terms and definitions used in the documentation. • Status – Indicator of whether the documentation is a prerelease or final version. • Source – Citation for the source of the marked-up documentation.

4. Section 2: Study Description • Citation– Bibliographic information for the data collection (not the documentation). • Scope– Information about the study’s subject, geographic & temporal coverage. • Methodology & Process– Information about how the data were collected (e.g., sample design). • Data Access – Access conditions & terms of use for the data collection. • Other Study Description Materials

5. Section 3: File Description • Name, contents, structure and dimensions (e.g., number of cases and record lengths) of each file in the collection. • Uses XML ID/IDREF mechanism to indicate which elements in study description apply to particular files

6. Section 4: Data Description • Variable Group–Groups variables that share a common subject, are coded from a single question, or are linked in some other way. • Variable–Name, weighting, valid/invalid ranges, etc. • Variable Group uses ID/IDREF to indicate which variables are in the grouping.

7. Section 5: Other Material • Allows for the inclusion of other materials that are related to the study as identified and labeled by the person doing the mark-up (e.g., bibliography, reports, etc.) • A "container" for other machine-readable materials such as data definition statements, PDF or scanned facsimile of the codebook, etc.