R4 Ballot #1 (Mixed Normative/Trial use) Release 4

This page is part of the FHIR Specification (v3.3.0: (v4.0.1: R4 Ballot 2). - Mixed Normative and STU ) in it's permanent home (it will always be available at this URL). The current version which supercedes this version is 5.0.0 . For a full list of available versions, see the Directory of published versions . Page versions: R5 R4B R4 R3 R2

2.5.3 Extension - Detailed Descriptions

FHIR Infrastructure Work Group Maturity Level : 5 Normative Ballot Standards Status : Normative
Normative Candidate Note:
This page is candidate normative content for R4 in has been approved as part of an ANSI standard. See the Infrastructure Package . Once normative, it will lose it's Maturity Level, and breaking changes will no longer be made. for further details.
Extension
Standards Status This element has a standards status of "Normative" which is different to the status of the whole resource
Definition

Optional Extension Element - found in all resources.

Control Cardinality 1..1 0..*
Type Element
Requirements

The ability to add extensions in a structured way is what keeps FHIR resources simple.

Invariants :
Defined on this element
ext-1 : Rule Must have either extensions or value[x], not both ( expression extension.exists() != value.exists(), xpath: exists(f:extension)!=exists(f:*[starts-with(local-name(.), 'value')])) value.exists()
Extension.url
Definition

Source of the definition for the extension code - a logical name or a URL.

Control Cardinality 1..1
Type uri
Comments

The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.

Extension.value[x]
Definition

Value of extension - may must be a resource or one of a constrained set of the data types (see Extensibility in the spec for a list).

Control Cardinality 0..1
Type *
[x] Note See Choice of Data Types for further information about how to use [x]