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Element-definition Extensions for use by FHIR Implementers

FHIR Infrastructure Work GroupMaturity Level: N/ABallot Status: Informative

Scope and Usage

This profile defines extensions that can be used to describe the additional characteristics that must be held by a data element.

Data elements can be defined in several places. The extensions defined within this profile may apply to most or all of these:

  • Profile.structure.element.definition - defining the characteristics of the data element when used according to the profile
  • Profile.extensionDefn.definition - defining the characteristics of the extension, regardless of where it is used
  • - defining the characteristics of permitted answers

Note: Implementations are not required to reject invalid data. However, transmitting data that violates one of these extensions would be considered invalid against the resource that declared the extension.

The extensions provided here fall into several categories:


minLengthminLength :

The minimum number of characters that must be present in the simple data type to be considered a "valid" instance.

regexregex :

A regular expression that defines the syntax for the data element to be considered valid.

entryFormatentryFormat :

Additional instructions for the user to guide their input (i.e. a human readable version of a regular expression like "nnn-nnn-nnn"). In most UIs this is the placeholder (or 'ghost') text placed directly inside the edit controls and that disappear when the control gets the focus.

minValueminValue :

The inclusive lower bound on the range of allowed values for the data element.

maxValuemaxValue :

The inclusive upper bound on the range of allowed values for the data element.

maxDecimalPlacesmaxDecimalPlaces :

Identifies the maximum number of decimal places that may be specified for the data element.

mimeTypemimeType :

Identifies the kind(s) of attachmemt allowed to be sent for an element.

maxSizemaxSize :

For attachment answers, indicates the maximum size an attachment can be.