---
title: "Structure Definitions"
canonical: "https://wiki.patientsknowbest.com/space/api/3364946016/Structure%20Definitions"
format: markdown
---
PKB will use an[ ](https://www.google.com/url?q=https%3A%2F%2Fwww.hl7.org%2Ffhir%2FSTU3%2Fextensibility.html&sa=D&sntz=1&usg=AOvVaw3PQnE-9RluoApvoRyLCS3h)[extension](https://www.hl7.org/fhir/STU3/extensibility.html) whenever we need to return information not captured by the core FHIR® specification.

Each extension has a subpage in this section.

Additionally, this section contains subpages explaining how PKB has mapped non-FHIR data into FHIR resources. These mapping pages document how we have populated each element in the resource.