This page is part of the FHIR Specification (v1.8.0: STU 3 Draft). The current version which supercedes this version is 5.0.0.  For a full list of available versions, see the Directory of published versions 
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Detailed Descriptions for the elements in the extension.
| Extension | |
| Definition | Mark that an invariant represents 'best practice' rule - a rule that implementers may choose to enforce at error level in some or all circumstances.  | 
| Control | 0..1 This element is affected by the following invariants: ele-1 | 
| Comments | Validators may/should offer implementers the choice to enforce invariants labelled as 'best practice' as errors not warnings.  | 
| Invariants | Defined on this element ele-1: All FHIR elements must have a @value or children (xpath: @value|f:*|h:div) ext-1: Must have either extensions or value[x], not both (xpath: exists(f:extension)!=exists(f:*[starts-with(local-name(.), 'value')]))  | 
| Extension.id | |
| Definition | unique id for the element within a resource (for internal references). This may be any string value that does not contain spaces.  | 
| Control | 0..1 | 
| Type | string | 
| Extension.extension(extension) | |
| Definition | An Extension  | 
| Control | 0..0 | 
| Type | Extension | 
| Extension.url | |
| Definition | Source of the definition for the extension code - a logical name or a URL.  | 
| Control | 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.  | 
| Fixed Value | http://hl7.org/fhir/StructureDefinition/elementdefinition-bestpractice | 
| Extension.value[x] | |
| Definition | Value of extension - may be a resource or one of a constrained set of the data types (see Extensibility in the spec for list).  | 
| Control | 1..1 | 
| Terminology Binding | Indicates the countries, regions, disciplines and other aspects of use within which this artifact is targeted for use. The codes SHALL be taken from Context of Use ValueSet; other codes may be used where these codes are not suitable  | 
| Type | Choice of: boolean, CodeableConcept | 
| [x] Note | See Choice of Data Types for further information about how to use [x] |