---
type: "codesystem"
title: "Type Derivation Rule"
codesystem: "type-derivation-rule"
---
# Type Derivation Rule

- **Official URL**: http://hl7.org/fhir/type-derivation-rule
- **Version**: 6.0.0
- **Status**: active
- **Name**: TypeDerivationRule
- **Title**: Type Derivation Rule
- **Publisher**: HL7 (FHIR Project)
- **Description**: How a type relates to its baseDefinition.
- **Case Sensitive**: true
- **Content**: complete

## Concepts

| Code | Display | Definition |
| --- | --- | --- |
| specialization | Specialization | This definition defines a new type that adds additional elements and optionally additional rules to the base type. |
| constraint | Constraint | This definition adds additional rules to an existing concrete type. |

## CodeSystem XML



```xml
<?xml version="1.0" encoding="UTF-8"?>

<CodeSystem xmlns="http://hl7.org/fhir">
  <id value="type-derivation-rule"/>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-wg">
    <valueCode value="fhir"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status">
    <valueCode value="normative"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm">
    <valueInteger value="5"/>
  </extension>
  <url value="http://hl7.org/fhir/type-derivation-rule"/>
  <identifier>
    <system value="urn:ietf:rfc:3986"/>
    <value value="urn:oid:2.16.840.1.113883.4.642.4.674"/>
  </identifier>
  <identifier>
    <use value="old"/>
    <system value="urn:ietf:rfc:3986"/>
    <value value="urn:oid:2.16.840.1.113883.4.642.1.660"/>
  </identifier>
  <version value="6.0.0"/>
  <name value="TypeDerivationRule"/>
  <title value="Type Derivation Rule"/>
  <status value="active"/>
  <experimental value="false"/>
  <date value="2021-01-05T10:01:24+11:00"/>
  <publisher value="HL7 (FHIR Project)"/>
  <contact>
    <telecom>
      <system value="url"/>
      <value value="http://hl7.org/fhir"/>
    </telecom>
    <telecom>
      <system value="email"/>
      <value value="fhir@lists.hl7.org"/>
    </telecom>
  </contact>
  <description value="How a type relates to its baseDefinition."/>
  <caseSensitive value="true"/>
  <valueSet value="http://hl7.org/fhir/ValueSet/type-derivation-rule"/>
  <content value="complete"/>
  <concept>
    <code value="specialization"/>
    <display value="Specialization"/>
    <definition value="This definition defines a new type that adds additional elements and optionally additional rules to the base type."/>
  </concept>
  <concept>
    <code value="constraint"/>
    <display value="Constraint"/>
    <definition value="This definition adds additional rules to an existing concrete type."/>
  </concept>
</CodeSystem>
```