While this statement and the diagram below it imply that CDex doesn't define any content that is exchanged, but instead defines profiles that constrain HRex and FHIR when a payer accesses data from an EMR, it should be explicitly called out so that it's clear to the reader.

As illustrated in figure 1 below, this guide is built on top of FHIR and other implementation guides that provide more and more focused use cases by constraining profiles and extending functionality to cover gaps.

Suggestion: Add some text that says "This guide does not define the content that will be exchanged. The content is defined in HRex"