A set of design principles has been identified during the course of the various DDI sprints. The list is shown below:
- Interoperability and Standards – The model is optimized to facilitate interoperability with other relevant standards.
- Simplicity – The model is as simple as possible and easily understandable by different stakeholders.
- User Driven – User perspectives inform the model to ensure that it meets the needs of the international DDI user community.
- Terminology – The model uses clear terminology and when possible, uses existing terms and definitions.
- Iterative Development – The model is developed iteratively, bringing in a range of views from the user community.
- Documentation – The model includes and is supplemented by robust and accessible documentation.
- Lifecycle Orientation – The model supports the full research data lifecycle and the statistical production process, facilitating replication and the scientific method.
- Reuse and Exchange – The model supports the reuse, exchange, and sharing of data and metadata within and among institutions.
- Modularity – The model is modular and these modules can be used independently.
- Stability – The model is stable and new versions are developed in a controlled manner.
- Extensibility – The model has a common core and is extensible.
- Tool Independence – The model is not dependent on any specific IT setting or tool.
- Innovation – The model supports both current and new ways of documenting, producing, and using data and leverages modern technologies.
- Actionable Metadata – The model provides actionable metadata that can be used to drive production and data collection processes.
Additional lower-level principles have surfaced during initial DDI model development:
- Remodeling Discouraged – The model leverages existing structures in the specification whenever possible to avoid inefficiencies.
- Objects Represent Actual Things – The model includes objects that are functional and are used.
- Separation of Logical and Physical – The model supports a distinction between logical and physical representations.
- Names are Mutable – The model contains names and labels that may change to encourage accessibility.
- Common Expressions – The model will only have features that reflect the common expressive capabilities of supported syntaxes/technologies (e.g., no multiple inheritances)
These principles are needed to inform the design of DDI 4.0, and to assist in decision-making during development and maintenance of the standard in future.