Subscriptions
Subscriptions are an essential capability the Founda Health Platform offers. Subscriptions allow application Clients to be notified of particular (clinical) events that are happening at the Provider Organizations they interact with. Subscriptions are managed by the Founda Health Subscription Service. In order to understand what you can do with the Subscription Service and how the service works, the concept of Subscriptions is explained as a Founda Fundamental.
A Subscription represents a notification, sent by a Provider Organization, of an event that an Application Provider is interested in to receive.
You can think of a Subscription as a subscription you have on a newspaper. 🗞️
The news agent may have multiple newspapers to offer, but you are only interested in "The New York Times". In this example, the subscription represents the "contract" between you and the agent to send you the NYT daily and it likely defines how it is delivered (i.e. paper in your mailbox, or digital news paper via email).
An application Client can request a Subscription to one or more Subscription Topics that a Provider Organization has to offer. The Subscription Topic defines the event that is being subscribed to, e.g. the scheduling of an appointment, like the NYT newspaper in the above example. The Subscription is the "contract" between a Provider Organization and an application Client to be notified when the conditions defined by the Subscription Topic are met.
Hence, three concepts are relevant to understand:
Subscription
The actual agreement between a Provider Organization and a Client, for the Client to be notified when a pre-defined event happens at the Provider Organization.
Subscriptions follow the FHIR R4b subscription resource definition and allow an application Client to manage its subscriptions it has with a Provider Organization. A Subscription also defines how a Client wishes to be notified (e.g. rest-hook).
Subscription Topic
The definition of the pre-defined event a Client can subscribe to in order to be notified.
A Subscription Topic follows the FHIR R4b subscriptionTopic definition. A Topic defines the "real world" event that triggers a Subscription to be activated, and a notification to be sent.
Subscription Topic Catalog
The collection of Subscription Topics that are defined and activated by a Provider Organization and exposed to the Application Provider to choose from.
The master catalog includes pre-defined Subscription Topics for all the well-known HL7v2 trigger events, such as Admission, Discharge and Transfer (ADT), Order Entry (ORM) and Scheduling (SIU).
Similar to the Client Authorization, every Subscription request requires explicit authorization by the Provider Organization before it becomes active. Setting up the Subscription Topic Catalog, as well as requesting a new Subscription can be done through the Founda Console.
In a healthcare setting, clinical events such as patient registration, patient discharge or an order being placed may be interesting events for applications to act upon. For example: a home monitoring system needs to be notified when a patient is discharged, or a patient questionnaire app needs to be informed when a patient is scheduled for a specific surgery. When such events are broadcasted through HL7v2 messages, they can be associated with a Subscription Topic. After a Client application has established an authorized Subscription to one (or more) of these topics, the application will be notified automatically every time this event occurs.
Subscriptions are very closely related to the Transformation Service. In many real-world use cases events are broadcasted through HL7v2 messages. The Founda Health Platform offers the capability to transform HL7v2 messages into a FHIR Bundle.
