---
type: "codesystem"
title: "Evidence Variable Constraint"
codesystem: "evidence-variable-constraint"
---
# Evidence Variable Constraint

- **Official URL**: http://hl7.org/fhir/evidence-variable-constraint
- **Version**: 6.0.0
- **Status**: active
- **Name**: EvidenceVariableConstraint
- **Title**: Evidence Variable Constraint
- **Publisher**: HL7 (FHIR Project)
- **Description**: A rule, such as a format or other expectation, for the data values.
- **Case Sensitive**: true
- **Content**: complete

## Concepts

| Code | Display | Definition |
| --- | --- | --- |
| alphanumeric-only | Alphanumeric Characters Only | String values that are restricted to only numbers and letters [A-Za-z0-9]. |
| alphanumeric-space-only | Alphanumeric and Space Characters Only | String values that are restricted to only numbers, letters, and spaces [A-Za-z0-9\s]. |
| range-zero-to-one | Range Zero to One | Numeric value between 0 and 1, inclusive. |

## CodeSystem XML



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

<CodeSystem xmlns="http://hl7.org/fhir">
  <id value="evidence-variable-constraint"/>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-wg">
    <valueCode value="cds"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status">
    <valueCode value="informative"/>
  </extension>
  <extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm">
    <valueInteger value="1"/>
  </extension>
  <url value="http://hl7.org/fhir/evidence-variable-constraint"/>
  <version value="6.0.0"/>
  <name value="EvidenceVariableConstraint"/>
  <title value="Evidence Variable Constraint"/>
  <status value="active"/>
  <experimental value="false"/>
  <date value="2024-11-14T10:01:24+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="A rule, such as a format or other expectation, for the data values."/>
  <caseSensitive value="true"/>
  <valueSet value="http://hl7.org/fhir/ValueSet/evidence-variable-constraint"/>
  <content value="complete"/>
  <concept>
    <code value="alphanumeric-only"/>
    <display value="Alphanumeric Characters Only"/>
    <definition value="String values that are restricted to only numbers and letters [A-Za-z0-9]."/>
  </concept>
  <concept>
    <code value="alphanumeric-space-only"/>
    <display value="Alphanumeric and Space Characters Only"/>
    <definition value="String values that are restricted to only numbers, letters, and spaces [A-Za-z0-9\s]."/>
  </concept>
  <concept>
    <code value="range-zero-to-one"/>
    <display value="Range Zero to One"/>
    <definition value="Numeric value between 0 and 1, inclusive."/>
  </concept>
</CodeSystem>
```