DDI is a very flexible and complex standard that may be used by various projects or organizations in “customized” ways that best answer specific needs. DDI profiles allow different agents or agencies to specify exactly how they use the DDI XML format, and thus help achieve seamless transfer and interoperability of DDI instances.
A DDI profile describes the subset of valid DDI objects used by an agency for a specified purpose. This is documented in a DDI-XML format, which allows a set of declarations to be made, identifying specific fields in the DDI which are “Used” or “Not Used”. Various other qualifications can be made to restrict or default permitted values for specific elements, and human-readable documentation can be added.
Survey Metadata Reusability and Exchange: A Call to Action for Questionnaire Documentation
This collaborative statement calls upon the survey design, production and archiving communities to take leadership in facilitating survey metadata exchange through adoption of shared metadata standards for questionnaire and data description.
Creating a DDI Profile in DDI-Lifecycle
DDI-Lifecycle Profiles for specific data
Recommended elements sets:
The full DDI Codebook specification was designed as a superset of elements providing an extensive coverage of social science data documentation. Many DDI users expressed the need for a "lighter" version of the specification that would contain a selection of the most relevant and commonly used DDI tags. In response to these requests, a recommended set of DDI elements is provided as a good basic framework for marking up documentation. The DDI Lite version is not a separate specification, but rather a subset of the full DDI Codebook model, and it is based on the earlier DTD version, not XML schemas.
To develop DDI Lite, several other metadata standards were reviewed to select elements that appeared to be either common across standards or critical to best practice in the documentation of social science data.
The CESSDA/IDC main use of metadata is geared towards possibilities to search for and locate information, basically from the substantive content of metadata. Provides guidelines for mandated and recommended elements.
This chart breaks down the elements by type and organization (IHSN, CESSDA, NSD, etc.)
XML example of a core set of elements in 3.0 provided by ICPSR.