Technical information

DDA landing page format

The landing page format is a expanded version of the German da|ra project to fit the needs of DDA. The DDA landing page is a subset of the information contained in DDI-L and drives the rendering of the HTML page. The result HTML page is embedded with schema.org tags for optimal search engine indexing.

The URL structure of the landing page is REST-based, -starting with catalouge / study identifier. E.g.:

  • http://dda.dk/catalogue/10

The next level 'doc' contains the documentation of the study: Currently the codebook and the DDA landing page format itself in XML.

  • http://dda.dk/catalogue/10/doc/codebook
  • http://dda.dk/catalogue/10/doc/ddastudymetadata

The XML schema definition for DDA landing page format is available at:
DDA landing page XML schema

DDA controlled vocabularies

DDA applies controlled vocabularies describing study level description -method and life cycle events. The controlled vocabularies are defined in Genericode format and utilized by DDA landing page format and DDI-L documentation.

Download and documentation of DDA CV's

DDA Kind Of Data


CV defining kind of data

DDA Time Method


CV defining time methodology

DDA Analysis Unit


CV defining analysis units in a study

DDA Data Collection Methodology


CV defining data collection methodology

DDA Mode Of Collection


CV defining modes of data collection

DDA Collection Situation


CV defining context in the data collection situation

DDA Sampling Procedure


CV defining sampling procedures

DDA Study State


CV defining the state of a study within DDA's curation proccess

DDA Study State


CV defining the state of a study within DDA's curation proccess

DDA Access Conditions


CV defining DDA access conditions

Search API documentation

The Indexingplatform exposes its simple search capabilities as a web service. The web service can be accessed in two ways either via URL parameters or via embedding the search parameters as XML in the request (see XML schema documentation). The service can search within:
  • Study unit description
  • Variable labels and description
  • Question texts and description
  • Universe descriptions and label
  • Concept descriptions and labels
  • Category texts

URL parameter method

With parameters:

  • search-string - the search string - [mandatory]
  • hits-perpage - number of hit pr. page with a maxium of 500 - [optionel]
  • hit-start - results will start at result number - [optionel]
  • lang - defined result language - [optionel] all language results will be outputed
  • StudyUnit - true - [optionel]
  • Variable - true - [optionel]
  • QuestionItem - true - [optionel]
  • Universe - true - [optionel]
  • Concept - true - [optionel]
  • Category - true - [optionel]

Example of a search with URL parameters:


XML embedded method

The search API URL is the same as with the URL parameter method but the URL parameters are striped and XML is added as payload. The XML is defined by the simple-search-parameters.xsd XML schema. E.g. using 'curl' a request would look like:

curl -d '<ssp:SimpleSearchParameters xmlns:s="http://dda.dk/ddi/scope" xmlns:ssp="http://dda.dk/ddi/simple-search-parameters" xmlns:smd="http://dda.dk/ddi/search-metadata" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><ssp:search-string>European</ssp:search-string><smd:SearchMetaData hits-perpage="50" hit-start="1" lang="da"/><s:Scope><s:StudyUnit/></s:Scope></ssp:SimpleSearchParameters>' -H 'Content-Type: text/xml' http://dda.dk/search-api

Search output format JSON or XML

The output of the API search can be both a JSOn or a XML format -the default is XML. For JSON add a HTTP accept request this option is valid for both types of search API methods.

E.g. using 'curl' for a JSON request the URL parameter method would take the form of:
curl 'http://dda.dk/search-api?StudyUnit=true&search-string=European' -H 'Accept: application/json'

XML schema documentation

XML schema file defining the input and outputs of search results and search parameters.

DDI URN resolution service

The DDI URN resolution service is based on the DDI-L URN standard. The service is a web service for retrieval of metadata elements identified by agency, ID and version.

The URL for the DDI-L URN service is: http://dda.dk/urn-resolution/ddi-3.1 with the parameter 'urn'

E.g. the URL for the DDI-L study unit with agency: dda.dk, ID: 18465 at version: 1.0.0 is:


Source code and licence

The Indexingplatform is maintained by the Danish Data Archive and licensed under the LGPL license and accessible at: github.com/DanishDataArchive/indexingplatform