Reference metadata or quality reports describe the concepts and methodologies used for collecting and generating data. They also provide information on the quality of the data. In this way they help users to correctly interpret the data.
Currently, the KAS uses two standard forms for documenting reference metadata: ESMS (Structure of Euros Methods SDMX) and ESQRS (ESS Quality Reporting Structure) which are standards used in the European Statistical System.
The purpose of ESMS format reports is to document methodologies, quality aspects, and statistical production processes in general, while ESQRS format reports provide more information to assess the quality of data.