ISO/HL7 27951:2009 - Overview
ISO/HL7 27951:2009, "Health informatics - Common terminology services, release 1" (first edition, 2009-11-15), defines an international framework for the development of an application programming interface (API) that messaging software can use to access terminological content. The standard is explicitly scoped as a framework for terminology-access APIs and is not intended to be a complete terminology service on its own. It was developed jointly by ISO and HL7 to improve consistent, interoperable access to clinical terminologies.
Key topics
The standard focuses on the design and interoperability of terminology-access APIs. Key technical topics and requirements you can expect from ISO/HL7 27951:2009 include:
- API framework and service model for accessing terminological content in messaging and clinical systems
- Data access patterns for retrieving concepts, codes and associated metadata from terminology sources
- Support for terminology operations commonly required by health applications (e.g., lookup, code translation/mapping, value-set handling and subset extraction)
- Versioning and provenance considerations to ensure consistent interpretation of coded data over time
- Conformance and interoperability guidance so client and server implementations can interoperate across vendors and jurisdictions
- Security and access control considerations appropriate to sensitive clinical terminological content
(Notes: the standard defines the framework and requirements rather than prescribing a single runtime implementation; specific operation names and protocol bindings are implementation choices built to conform to the framework.)
Applications
ISO/HL7 27951:2009 is practical for organizations and projects that need standardized access to clinical terminologies:
- EHR and clinical application vendors implementing terminology lookup and validation features
- Interface and messaging developers building HL7-based message flows that embed coded clinical data
- Terminology authorities and service providers exposing code systems (SNOMED CT, LOINC, ICD, local code sets) via APIs
- Health information exchanges (HIEs) and national/regional programs that require consistent term resolution and mapping across systems
- Clinical decision support and analytics platforms that rely on stable code interpretation and value-set expansion
Related standards
ISO/HL7 27951:2009 complements HL7 messaging and other ISO health-informatics standards by defining how terminology content should be accessed programmatically. Implementers typically use it alongside HL7 profiles and relevant national terminology policies to achieve interoperability.
Keywords: ISO/HL7 27951:2009, common terminology services, terminology API, health informatics, interoperability, terminology management, HL7, code systems, value sets.
