> For the complete documentation index, see [llms.txt](https://docs.geoprismregistry.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.geoprismregistry.com/readme/current/deployment-and-setup/3.7-fhir-custom-implementation.md).

# 3.7. FHIR custom implementation

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This documentation covers advanced system configuration.
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These transformations are what is used when importing or exporting data through an External Synchronization from or to a FHIR instance.
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The data coming in and out of a Fast Healthcare Interoperability Resources (FHIR) instance is transformed through the use of the Java Service IOC architecture. A developer can add a new transformation by creating a JAR file that registers its classes as implementations of the FHIR interfaces. The following sections describe a step-by-step process to create a new FHIR implementation in the system.