This document specifies content-related aspects of terminology database maintenance. It gives guidance on the content of terminological data collections, with emphasis on data quality evaluation.This document gives guidance for modellers of concept entries who need to ensure interoperability and high-quality content. It aims to ensure that terminological data collections themselves meet high standards for design conformity with standards such as ISO 12620-1 and ISO 16642, data accuracy and performance. It outlines principles for assuring data quality (see ISO 9001) and evaluating terminological data collections for purposes of continuous improvement. This approach contrasts that of ISO 23185:2009, which focuses on the usability of existing terminology resources.This document does not apply to the management of text corpora or to term extraction tools.