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FHIRcast
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FHIRcast, published by HL7 International / Infrastructure And Messaging. This guide is not an authorized publication; it is the continuous build for version 3.0.0-ballot built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/fhircast-docs/ and changes regularly. See the Directory of published versions

Conformance

Page standards status: Informative

The FHIRcast specification can be described as a set of capabilities and any specific FHIRcast Hub may implement a subset of these capabilities. A FHIRcast Hub declares support for FHIRcast and specific capabilities by exposing an extension on the FHIR CapabilityStatement resource as described below.

Wellknown Endpoint

To support various architectures, including multiple decentralized FHIRcast hubs, the Hub exposes a .well-known endpoint containing additional information about the capabilities of that Hub. A Hub's supported events, version, and other capabilities can be exposed as a Well-Known Uniform Resource Identifiers (URIs) (RFC5785) JSON document.

Hubs SHALL serve a JSON document at the location formed by appending /.well-known/fhircast-configuration to their hub.url. Contrary to RFC5785 Appendix B.4, the .well-known path component may be appended even if the hub.url endpoint already contains a path component.

A simple JSON document is returned using the application/json mime type, with the following key/value pairs:

Field Optionality Type Description
eventsSupported Required array Array of FHIRcast events supported by the Hub.
websocketSupport Required (deprecated) boolean SHALL have the static value: true - indicating support for websockets. FYI to Implementers: Given that websocket support is the only defined communication method in FHIRcast versions STU3 and was required in STU2, it's likely that this element will become Optional and then Deprecated in the future.
fhircastVersion Optional string Specific FHIRcast IG Version supported by Hub (for example: 2.0.0 or 3.0.0). Hubs SHOULD indicate the version of FHIRcast supported. See history page for versions.
getCurrentSupport Optional (deprecated) boolean true or false - indicating support for the "Get Current Context" API. FYI to Implementers: Note that this element is being deprecated in favor of the capabilities array. Expect this element to be removed in the future. In the interim, capable implementers should support both this element and the capabilities array.
capabilities Optional array Array of key-value pairs representing supported topics. See Capabilities table below for list of defined keys and their meanings.
fhirVersion Optional string DSTU1, DSTU2, STU3, R4, R4B, or R5 - indicating the specific version of FHIR for this Hub.

A field of webhookSupport SHALL be ignored.

Capabilities

Field | Optionality | Type | Description —————— | ———– | —– | — supportsGetCurrentContext | Optional | Boolean | true or false - indicating support for the "Get Current Context" API. supportsNonCurrentContextUpdates | Optional | Boolean | true or false - indicating support for the "Update Events Outside of Current Context"

Wellknown endpoint discovery example

In this example the Hub URL is "www.hub.example.com/".

Wellknown endpoint discovery Request
GET /.well-known/fhircast-configuration HTTP/1.1
Host: www.hub.example.com

Wellknown endpoint discovery Response

HTTP/1.1 200 OK
Content-Type: application/json

{
  "eventsSupported": ["Patient-open", "Patient-close", "SyncError", "com.example.researchstudy-transmogrify"],
  "websocketSupport": true,
  "fhircastVersion": "3.0.0"
  "capabilities": [
    "supportsGetCurrentContext": false,
    "supportsNonCurrentContextUpdates": false
  ]
}

FHIR Capability Statement

To supplement or optionally identify the location of a FHIRcast hub, a FHIR server MAY declare support for FHIRcast using the FHIRcast extension on its FHIR CapabilityStatement's rest element. Note that client-side Hubs without a client-side FHIR server likely will not support communicating the url of a hub in this extension. See the FHIRcast CapabilityStatement profile.

FHIR Resource Structures

FHIRcast defines profiles for various FHIR resource structures used in the specification, see summary of artifacts.

Must Support

In the context of FHIRcast, must support (MS) on any data element SHALL be interpreted to mean FHIR’s MustSupport. Generally, implementations are expected to:

  • if known and possible, populate supported data elements as part of the event notifications as specified by the FHIRcast profiles.
  • interpret missing, supported data elements within resource instances as data not present in the sending systems (or for which the requestor is unauthorized).