> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metriport.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Signature

> Base StructureDefinition for Signature Type: A signature along with supporting context. The signature may be a digital signature that is cryptographic in nature, or some other signature acceptable to the domain. This other signature may be as simple as a graphical image representing a hand-written signature, or a signature ceremony Different signature approaches have different utilities.

## Properties

| Name         | Required | Type                                                                                                                                                                                                                                                                                                                                                            | Description                                                   |
| ------------ | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------- |
| id           | No       | string                                                                                                                                                                                                                                                                                                                                                          | Unique id for inter-element referencing                       |
| extension    | No       | [Extension](/medical-api/fhir/data-types/extension)\[]                                                                                                                                                                                                                                                                                                          | Additional content defined by implementations                 |
| type         | Yes      | [Coding](/medical-api/fhir/data-types/coding)\[]                                                                                                                                                                                                                                                                                                                | Indication of the reason the entity signed the object(s)      |
| when         | Yes      | instant                                                                                                                                                                                                                                                                                                                                                         | When the signature was created                                |
| who          | Yes      | Reference\<[Practitioner](/medical-api/fhir/resources/practitioner) / [PractitionerRole](/medical-api/fhir/resources/practitionerrole) / [RelatedPerson](/medical-api/fhir/resources/relatedperson) / [Patient](/medical-api/fhir/resources/patient) / [Device](/medical-api/fhir/resources/device) / [Organization](/medical-api/fhir/resources/organization)> | Who signed                                                    |
| onBehalfOf   | No       | Reference\<[Practitioner](/medical-api/fhir/resources/practitioner) / [PractitionerRole](/medical-api/fhir/resources/practitionerrole) / [RelatedPerson](/medical-api/fhir/resources/relatedperson) / [Patient](/medical-api/fhir/resources/patient) / [Device](/medical-api/fhir/resources/device) / [Organization](/medical-api/fhir/resources/organization)> | The party represented                                         |
| targetFormat | No       | code                                                                                                                                                                                                                                                                                                                                                            | The technical format of the signed resources                  |
| sigFormat    | No       | code                                                                                                                                                                                                                                                                                                                                                            | The technical format of the signature                         |
| data         | No       | base64Binary                                                                                                                                                                                                                                                                                                                                                    | The actual signature content (XML DigSig. JWS, picture, etc.) |