[nradov]

The Epic ecosystem is actually pretty open now. They have multiple web service APIs with full documentation, and even provide a developer sandbox you can use to test client applications.

https://open.epic.com/

Epic also has an app store. You can write your own SMART on FHIR apps, then deploy them inside the EHR with full access to patient data.

https://apporchard.epic.com/

[arkh]

The full FHIR standard can be a lot at first sight https://www.hl7.org/fhir/ but I'd recommend anyone having to store names, addresses or contact information to check how they do it. The last example for names is always fun: https://www.hl7.org/fhir/datatypes-examples.html#HumanName