## Introduction This DHDR FHIR specification defines the FHIR profiles (constraints) and extension elements that are used in the DHDR project. All FHIR-based specifications rely on an underlying set of base “resources”. ### Resources Resources are the building blocks of the FHIR standard. These resources convey the content of clinical records, identify patients or providers, or otherwise support messaging between systems. These resources have been developed by several working groups at HL7, based on members’ experience and subject expertise. These resources are intended to capture and support 80% of all implementation use case requirements; projects are encouraged to meet the remaining 20% of requirements through extensions and profile constraints. The list of all available resources in the FHIR standard can be found at https://hl7.org/fhir/resourcelist.html, with additional details at https://hl7.org/fhir/resourceguide.html. ### Profiles Resources defined in the FHIR standard are intended to support a wide variety of use cases, resulting in a large number of available elements, and very few constraints. Implementers are encouraged to create and apply FHIR Profiles, which places constraints on the defined FHIR resources – tightening cardinality, identifying unused/unsupported elements, defining value sets for elements, and adding extension elements. ### Transmission Specification The formal MIME-type for FHIR resources is application/fhir+json or application/fhir+xml. The correct mime type SHALL be used by clients and servers: