In Estonia, all databases are responsible for describing their kept information in the catalogue of interoperability resources (RIHA). Following the once-only principle, collecting the same data in separate databases is not allowed. RIHA serves as the national registry of systems, components, services, data models, semantic assets, and more. The purpose of RIHA is to guarantee the transparent, balanced, and efficient management of public sector information systems. Registration with RIHA for public databases and information systems is mandatory and enforced by law.
Among some of the most popular digital services in Estonia are: the Tax and Customs Board, the Patient Portal, e-File, and the e-Business Register.