Overview
ISO 21549-8:2010 - Health informatics - Patient healthcard data - Part 8: Links specifies a standardized model for storing and expressing references (links) on patient healthcards to distributed clinical and administrative records. The standard defines the structure and elements of link entries (how to represent URIs, identifiers and descriptive metadata) so that healthcards can point reliably to external data objects held across different systems or organisations. Note: access control, data protection, access methods and other security services are explicitly outside the scope.
Key topics and technical requirements
- Purpose: Facilitate access to distributed patient records and subcomponents using healthcards by providing unambiguous references and linkage information.
- Core structure: Each link contains a URI (physical reference and unique identifier such as an OID or proprietary ID), a description (characterization of the referenced data), and accessory attributes (originator, creation/collection dates, and optional constraints).
- Link types: Supports subtypes such as relay (extension points for data on the card) and standalone (independent references).
- Metadata elements: language, mediaType, usablePeriod, sizeReferenced, purpose, accessConditions and coding scheme references to characterize and limit use.
- Compatibility: Logical reference structure is designed to be compatible with healthcare messaging and document standards (e.g., HL7v3 / CDA) and URI syntax per IETF RFC 3986.
- Data definitions: ASN.1 data definitions for implementation are provided (Annex A); informative examples are in Annex B.
- Normative references: ISO 21549-2 (Common objects), ISO 21549-4 (Extended clinical data), HL7v3, IETF RFC 3986.
Applications and who uses it
ISO 21549-8 is practical for:
- Smart card and healthcard vendors implementing patient cards that link to off-card records.
- EHR/EMR system architects and vendors who need consistent, interoperable reference formats for distributed records.
- Health information exchange (HIE) projects and national eHealth programs that use cards as pointers to regional or national repositories.
- Clinical software integrators and middleware developers implementing URI/OID-based accessors or card readers.
- Hospitals, clinics and diagnostic centres that want portable, standardised pointers to images, reports or other data stored elsewhere.
Practical benefits include improved patient data discoverability, consistent linkage across systems, and reduced duplication of on-card storage by referencing larger external objects.
Related standards
- ISO 21549 series (Parts 1–7 cover structure, common objects, clinical and administrative data)
- ISO/IEC 9834 (OID management)
- HL7 v3 / CDA (clinical document architecture)
- IETF RFC 3986 (URI syntax)
Keywords: ISO 21549-8:2010, health informatics, patient healthcard, links, URI, OID, HL7, distributed patient records, healthcard links, smart card interoperability.