openEHR

openEHR is an open standard for electronic health records (EHRs) designed to enable semantic interoperability and long-term data preservation. It defines a two-layer architecture consisting of a stable Reference Model (RM) and a domain-specific Archetype Model (AM). The RM formalizes generic data structures, types, versioning, audit trails, privacy controls, and multi-user integrity, while the AM captures clinical concepts as archetypes that encode domain knowledge independent of software applications. Archetypes can be combined into templates to support particular clinical workflows.

Archetypes describe clinical concepts such as a blood pressure measurement or a laboratory result using a formal language, and are stored in archetype repositories. The separation of clinical knowledge from software allows interoperable data exchange across different systems and vendors, with data stored according to the RM remaining usable as applications evolve. The Archetype Definition Language (ADL/ADL2) underpins archetype specification, and archetypes are often localized for language and regional practice.

Data in an openEHR system can be queried using the Archetype Query Language (AQL), enabling retrieval of structured data based on archetypes rather than application-specific models. Templates provide constraints and localization for particular use cases and workflows, while the architecture supports robust audit trails and access controls for regulatory compliance and governance.

OpenEHR is stewarded by the OpenEHR Foundation and a network of national programs, vendors, and researchers. The specifications are openly published and maintained as an open, collaborative standard. The approach supports interoperability across heterogeneous health information systems and has been explored in pilots and national-scale initiatives in multiple regions.