Actors and Capabilities

Within technical frameworks, particularly HL7 FHIR Implementation Guides, Actor Definitions and Capability Statements are used as complementary artifacts to describe interactions between different systems. Together they clarify both in which roles an actor can participate in an exchange of information or other requests and which functions and behaviors an actor in that role is expected to support.

An Actor Definition describes the types of systems, users, or software components involved in a specific use case, as well as the role each actor plays. It establishes responsibilities, obligations, and expected behaviors, for example whether a system initiates requests or responds to them. By defining clear roles, such as requesting and responding systems, a shared understanding is created of how information exchange is intended to function within an ecosystem.

Capability Statements complement this by formally describing the actual or intended functionality of a system. They specify which FHIR resources and profiles are supported, which RESTful operations can be performed, which search parameters are available, and which requirements are mandatory or recommended. In this way, other systems can determine how to interact and verify that interoperability requirements are met.

The relationship between these two artifacts is fundamental: the Actor Definition defines the role, while the Capability Statement defines the technical FHIR capabilities and behaviors associated with that role. A system that claims conformance to a specific actor role must therefore also meet the requirements specified in the corresponding Capability Statement. This ensures consistent and predictable implementation of FHIR-based solutions.