In FHIR R4, topics are discovered by looking at the server
CapabilityStatement
for the
SubscriptionTopic Canonical Extension.
For this walkthrough, we will be using the included encounter-complete
topic that has a canonical URL of http://example.org/FHIR/SubscriptionTopic/encounter-complete
.
The current metadata for this server can be viewed
here,
or requested (in FHIR) at
https://subscriptions.argo.run/fhir/r4/metadata
.
Note that in FHIR R4, there is not an official required format for representing SubscriptionTopic
resources. Since topics are canonical resources, the expectation is that they will be defined
by authors (e.g., in Implementation Guides) and communicated out-of-band. For example, for
an "encounter-start" topic, both the server and client can function with only the
canonical URL and the understanding of what that topic represents.
With that said, one possible way of representing topics in FHIR R4 is to use the model provided
in FHIR R5, ported using FHIR cross-version support. This implementation supports topics defined via
that mechanism. Our included encounter-complete
topic is thus available on this server
at Basic/encounter-complete
or in FHIR at
https://subscriptions.argo.run/fhir/r4/Basic/encounter-complete
.
Click next to select the encounter-complete
topic.