The HSPC The Logica Reference Messaging system is designed to support FHIR Subscription resources and show how such patterns can be part of an enterprise content-based routing solution.
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The messaging system exists to support context-based routing of messages. The FHIR use case is to support the FHIR subscription resource. When a subscription is submitted to the API server (created, updated, deleted), the subscription is registered with the messaging system as a Drools rule based on the subscription criteria. When non-subscription resource (Observation, Patient, etc.) is submitted to the API server (created, updated, deleted), the resource is submitted to the messaging system for routing. If the resource matches (using Drools rules) the resource is routed according to the channel definitions of the subscription.
Alternatively, a back-end service could use a polling strategy to determine when any changes have occurred to the FHIR resources (for example, from an external data feed). This back-end service would then submit the resource to the messaging system for routing.
Bilirubin Monitor Application
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The second scenario the Bilirubin Monitor is interested in is creating alerts when Bilirubin observations are submitted that exceed dangerous thresholds. In this scenario, the monitor is send every Bilirubin observation that is received by the EHR. The monitor then queries the full Bilirubin resource to determine if the value has exceeded the threshold, then creates an alert.
Enterprise Integration Patterns
Conceptually, we are doing Publish-Subscribe using the FHIR Subscription model. However, internally we are using various Enterprise Integration Patterns, and technologies of including Drools for dynamic content based routing and (future) Apache Camel for light-weight routing. Alternatives to Camel include Spring Integration and Mule ESB.
Using a light-weight routing solution allows an enterprise to easily provide additional behavior. For example, the EHR FHIR interceptor can publish to a service bus.
