DDI Materials

DDI 4 is the version we are looking at for this workshop and the use together with other specs. The DDI Version 4 is currently in development. A prototype release will be published soon.

DDI 3 (Lifecycle) is the version which covers the data lifecycle approach and DDI 2 (Codebook) is intended for the description of a single study, the older understanding of a machine-readable codebook. Both are defined as XML Schema. Both are currently used in the community.

There is also the DDI-RDF Discovery Vocabulary (Disco), which is a RDF vocabulary in mature draft status. It is an approach of a couple of years ago to provide DDI for the Semantic Web. It provides some core features of DDI Codebook and Lifecycle for discovery purposes. It uses DCAT as well.

DDI 4 has a UML model from which representations/bindings can be generated. XML Schema (for preservation) and OWL (for discovery) are currently realized. More representations, like program libraries for Java, JSON, etc. are planned.

DDI 4 is a complex model. The class library comprehends currently 303 classes and 605 properties (it depends on the counting method). It is organized in packages for management purposes.

Views (subsets of the model) are defined for specific purposes or uses or user communities. This should enable easier access to the complex model. There is still work going on regarding this approach.

Large parts of DDI 4 are pretty independent from the social science domain. Especially data description, conceptual and workflows (for process description) seem to be quite useful for the cross-domain approach.

Most of these apply to a more detailed level like the variables.

But other parts might be also useful for the study level where other standards like DCAT are important.

The development platform of the DDI4 model is available at: http://lion.ddialliance.org/, which provides UML diagrams and detailed information on all classes, properties, packages, and views.

Conceptual: http://lion.ddialliance.org/package/conceptual

Logical Data Description: http://lion.ddialliance.org/package/logicaldatadescription

Data Management: http://lion.ddialliance.org/view/datamanagementview

Workflows: http://lion.ddialliance.org/package/workflows

With Conceptual, Logical Data Description and Workflows, UML diagrams are available on the bottom of these package pages. They are automatically generated and are therefore sometimes not very readable. By clicking on class names further information will be shown.

Data Management is a view built on top of classes from several packages including Workflows. It is being developed in collaboration with a data network that spans central and southern Africa that performs demographic and epidemiological surveillance.

The work process on DDI 4 is described in the DDI Moving Forward Process Summary. Full documentation on the DDI Moving Forward Project can be found on the DDI Collaboration Wiki.

Additionally, a description of data structures new in DDI 4 and their uses can be found here.