FHIR Data Type

The primary type for representing coded clinical data. It allows a concept to be described using multiple codings from different terminologies simultaneously, along with a plain text representation.

• coding: An array of Coding elements, each specifying a system (e.g., http://snomed.info/sct) and a code.
• text: A human-readable string, essential when no suitable code exists.
• Mechanism: Enables terminology translation by sending a SNOMED CT code and an ICD-10-CM code for the same diagnosis in one field.

A structured data type used to uniquely identify a real-world entity, such as a patient's medical record number or a national provider identifier. It binds an identifier value to a specific system and assigns a use context.

• system: A URI that defines the namespace for the identifier (e.g., urn:oid:2.16.840.1.113883.4.1 for NPI).
• value: The actual identifier string.
• use: A code specifying the context, such as usual, official, temp, or secondary.

A complex type for representing human names with full internationalization support. It parses a name into its constituent parts rather than treating it as a single string, enabling reliable indexing and display.

• Parts: Includes family, given, prefix, and suffix elements.
• Period: Allows tracking of name changes over time with an effective date range.
• use: Indicates the context, such as official, usual, maiden, or anonymous.

A data type for representing postal addresses with global applicability. It supports both structured components and a formatted text representation for systems that cannot parse the individual parts.

• Structured Parts: Includes line, city, district, state, postalCode, and country.
• type: Distinguishes between postal, physical, and both.
• use: Specifies context like home, work, temp, or old.

A simple but critical type that defines a time interval with a start and an end boundary. It is used across resources to specify durations for events, names, addresses, and clinical observations.

• Boundaries: Both start and end are optional, allowing for open-ended intervals.
• Precision: Boundaries are dateTime values, supporting varying precision from year down to second.
• Usage: Found in Observation.effectivePeriod, Patient.name.period, and MedicationRequest.dispenseRequest.validityPeriod.

A measured amount with a numeric value and a coded unit. It is the foundation for representing lab results, vital signs, and medication dosages, ensuring semantic interoperability of measurements.

• value: A decimal number.
• unit: A human-readable representation of the unit (e.g., mg/dL).
• system and code: A machine-processable UCUM code (e.g., mg/dL as mg/dL).
• Comparator: Optional operators like <, >, <=, >= for ranges.

The base scalar types that carry a single value. These are the atomic units of FHIR data.

• string: A sequence of Unicode characters.
• integer / decimal: Numeric values for counts and precise measurements.
• boolean: A true or false value.
• dateTime / date / time / instant: Temporal values with varying precision.
• uri / url / canonical: Strings that conform to specific URI formats for identification and linking.
• base64Binary: Arbitrary binary content encoded as a base64 string.
• code: A string that must match a defined pattern, typically used for controlled vocabularies.

Reusable structures composed of multiple elements, including other primitives or complex types. They define common patterns.

• Identifier: Uniquely labels an entity with a system and value pair.
• HumanName: Parses a person's name into components like given, family, and prefix.
• CodeableConcept: A value from a terminology system, including the code, display text, and coding system.
• Address: Structured postal address with street, city, state, and country.
• ContactPoint: A technology-mediated contact detail like a phone number or email.
• Quantity: A measured amount with a numeric value and a coded unit.
• Period: A time range defined by a start and end date/time.
• Ratio / Range: Structures for expressing relationships between quantities and bounded intervals.

A special type of complex data type that can only be used within a single resource and cannot be reused elsewhere. It defines the structure of repeating, nested components.

• Purpose: To model resource-specific, hierarchical data that has no meaning outside its parent context.
• Example: Patient.contact is a BackboneElement. It defines the relationship and contact details for a patient's emergency contact, a structure unique to the Patient resource.
• Key Distinction: Unlike a reusable complex type like Address, a BackboneElement is not defined globally and cannot be referenced by other resources.

A mechanism where a single element can be one of several possible data types, denoted by [x] in the element name.

• Function: Provides flexibility to represent a value in different ways depending on the context.
• Example: Observation.value[x] can be a Quantity (e.g., 140 mg/dL), a CodeableConcept (e.g., 'Positive'), a string, a boolean, or a Range.
• Serialization: The type is appended to the element name in the JSON, e.g., valueQuantity or valueCodeableConcept. This allows a single resource to handle diverse clinical findings.

FHIR data types are serialized consistently across formats, ensuring predictable parsing.

• Primitive in JSON: Represented as a JSON string, but can also carry an internal id and extension by using an object wrapper: "status": {"extension": [...], "value": "final"}.
• Complex in JSON: Represented as a JSON object with properties matching the element names.
• XML Representation: Primitives are attributes or simple elements, while complex types are nested elements. The value attribute is used for the actual primitive content when extensions are present.
• Consistency: The logical model is format-independent, guaranteeing that the same data structure is understood whether it's in JSON, XML, or RDF.

Standard profiles that constrain base data types for specific use cases, ensuring interoperability.

• SimpleQuantity: A profile on Quantity that forbids the use of a comparator, used for exact measurements.
• Money: A profile on Quantity that constrains the unit to a currency code.
• Age: A profile on Quantity where the unit is a time duration, typically used for patient age.
• Distance: A profile on Quantity where the unit is a measure of length.
• Count: A profile on Quantity with no unit, used for a discrete number of items.
• Purpose: These profiles provide semantic clarity and allow validators to enforce stricter rules than the base type definition.