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Reference Implementation

In drafting this specification, several reference implemention projects were created as a means of vetting core use cases and modeling decisions. None of these projects should be considered part of the specification proper, but are useful in evaluation and planning. They are subject to change without notice and are expected to do so from ongoing feedback.

Marketplace Service

The author(s) maintain a conceptual demonstration of the API, including a basic bi-directional WebSocket mechanism for Agent automation. At time of this writing a demo environment consistent with the original Automated Injection of Curated Knowledge Into Real-Time Clinical Systems dissertation prototypes is available by request from Preston Lee. The reference implementation provides a platform-specific model (PSM) for PostgreSQL, and itself is built to be distributable as a Product by an instance of itself. The demo further demonstrates the principle of self-bootstrapping an underlying, external database into the correct state without human intervention, and implements the same 12-Factor configuration injection and other principles required of all Products.

Platform-Specific Model (PSM)

 Reference Marketplace Service Platform-Specific Model

The reference implementation further provides an integrated WebSockets-based pub/sub mechanism at the /websockets endpoint, implemented using the space_elevator library (https://github.com/preston/space_elevator) to receive Platform-instance-specific messages over a stateful Marketplace server connection to demonstrate support for the automated point-and-click deployments envisioned of production environments.

Platform Integration Agent

While Platform integration is largely outside the scope of this specification -- that is largely a function of a customer's runtime platform -- it is useful to demonstrate how integration with a Marketplace instance may connect with local container orchestration. Limited example code showing connection and consumption of WebSocket events against the reference Marketplace Service.

Marketplace UI

While the Marketplace API does not define nor assume any GUI capabilities, it is often easier to illustrate the capabilities of the Marketplace’s functional model with a breathing, interactive example.

The reference Marketplace UI is a web application written to the Marketplace API, using modern web technologies and in mainstream development style. It authenticates using OAuth 2 and OpenID Connect in the same manner as SMART-on-FHIR, and visualizes how frontend-only web applications may be easily containerized to meet Build Packaging requirements. Like the reference Marketplace Service, it is also packaged to be distributed by a Marketplace instance.

A demo environment is available at Logica by request.

Full Example Products

Graphite Health has assembled a set of example products showcasing how different technology types can be packaged for marketplace publication, deployed to a runtime Platform, and integrated with OpenTelemetry-compatible collectors. Contact them for details.

SMART-on-FHIR - "Bilirubin" Product

A reimplementation of the bilirubin SMART-on-FHIR application originally developed by Logica Health, Graphite Health has developed an updated version for demonstrating marketplace.json metadata files and 12factor engineering principles necessary to automate distribution and deployment of such application software.

CDS Hooks - CDC Opioid Prescribing Guidelines

In 2021, Yale piloted an opioid prescribing CDS project to recommend urine toxicology screenings, when appropriate, using CDS Hooks and CDC's Opioid Prescribing Guidelines. This type of injectable CDS is a prime example of the type of CDS a Marketplace can automate distribution and deploy of. Graphite Health is actively collaborating to produce a reference implementation compatible with Marketplace packaging and metadata standards.

FHIR Resource Service - TBD

Products exposing FHIR endpoints will be exlicitly supported by the marketplace.json schema, and presents unique challenges due to the way CapabilitiesStatement is designed to work. We are actively seeking feedback on the most appropriate means of declaring service API compatibility metadata in a static manner that can be evaluated prior to running the Product.

Metered Static Content - TBD

Graphite Health is also actively working in this area to produce product packaging and metadata guidelines for static content types that require usage metering for licensing, billing, analytics or other purposes.