2.1 Understanding FHIR

This implementation guide is based on the HL7 FHIR standard. It uses terminology, notations and design principles that are specific to FHIR. Before reading this implementation guide, it's important to be familiar with some of the basic principles of FHIR as well as general guidance on how to read FHIR specifications. Readers who are unfamiliar with FHIR are encouraged to read (or at least skim) the following prior to reading the rest of this implementation guide.

• FHIR overview
• Developer's introduction
• (or Clinical introduction)
• FHIR data types
• Using codes
• References between resources
• How to read resource & profile definitions
• Base resource
• RESTful operations
• Search

Feel free to explore other aspects of the FHIR specification that you feel may be relevant or of interest.

2.1 Resources

This implementation guide defines profiles on several resources. Implementations are expected to be conformant with these profiles in order to be conformant with this implementation guide.

Based on FHIR Resource	SDC Profile(s)	Purpose
Questionnaire	SDC Questionnaire Profile	Used to define form definitions that may be downloaded for manual and/or automatic population
	Advanced Rendering Questionnaire Profile	Defines additional capabilities for controlling the rendering of the questionnaire.
	Advanced Behavior Questionnaire Profile	Defines additional capabilities for controlling data entry and calculating values within the questionnaire.
	Populateable Questionnaire Profile	Defines elements that support auto-population and pre-population of questionnaires
	Extractable Questionnaire Profile	Defines elements that allow conversion of a QuestionnaireResponse to a FHIR resource or Bundle of FHIR resources
	Adaptive Questionnaire Profile	Defines the metadata that should be present to embedding a adaptive Questionnaire as part of a QuestionnaireResponse
	Adaptive Questionnaire - search Profile	Defines the metadata that should be present to support searching for adaptive questionnaires.
QuestionnaireResponse	SDC Questionnaire Response Profile	Used to share instance data captured using questionnaire forms
	Adaptive Questionnaire Response Profile	Represents a response to a questionnaire that is dynamically built as each question is answered.
ValueSet	SDC Value Set Profile	Used to define collections of allowed values for data elements and for questions in questionnaires
CodeSystem	SDC Code System Profile	Used to define allowed values for data elements and for questions in questionnaires

Additional resources such as Patient, Practitioner, Binary, ConceptMap, StructureMap, Provenance, AuditEvent and others are also likely to be used in SDC solutions, though no SDC-specific profiles have been created for them.

2.2 Terminology Operations

In addition to the QuestionnaireResponse population operations, it will be useful for Form Filler and Form Manager systems to support some of FHIR's terminology service capabilities - specifically the Valueset Expand and Validate code operations.

2.3 Conformance and Must Support

FHIR defines the notion of Must Support to help establish conformance expectations for systems. The specific meaning of "must support" is left to be defined in individual implementation guides. For the purposes of this implementation guide, "must support" shall be interpreted as follows:

• Conformant systems SHALL be capable of sending and receiving the data element
• When a system persists a resource instance, all "must support" elements SHALL be persisted and retrieved with other elements
• Where an element affects the display or validation of a Questionnaire and a system performs either or both of those operations, the behavior established by the value of the element SHALL be performed

2.2 Understanding FHIRPath

In addition to the base FHIR specification, some of the more advanced capabilities defined in this implementation guide - specifically around behavior, population and extraction rely on the FHIRPath language. This is a path expression language that is independent of syntax. I.e. FHIRPaths written against a questionnaire will work the same regardless of whether the instance is expressed in XML, JSON, Turtle or some other syntax.

Implementers using any of these advanced questionnaire capabilities will need to be familiar with the FHIRPath Specification.

2.2.1 Questionnaire context

To support using FHIRPath with questionnaires, this implementation guide defines a set of additional FHIRPath contexts: TODO