Intro language should be revised to more accurately reflect the scope of the IG and better orient the reader about what to expect.

Some sample language is provided here (note changes to section titles as requested in FHIR-42279):

The National Directory of Healthcare Providers & Services (NDH) Implementation Guide (IG) provides standards and guidance for a national directory infrastructure in the US. The IG envisions a national source of truth for information about providers, health organizations, and related services, their relationships, and technical connectivity details (i.e., electronic endpoints). Content maintained by the national directory would be made available to downstream local directories using FHIR APIs. Local directories could also use FHIR APIs to make content available to their users. FHIR APIs could also serve as an entry point to the national directory, i.e., providers and organizations contribute information to the national directory over a FHIR API. Finally, the national directory may leverage FHIR APIs to facilitate verification of directory content for accuracy.

The sections of this IG provide guidance and/or standards for each of these capabilities:

• Base artifacts - provides a variety of FHIR artifacts including profiles, extensions, search parameters, and terminologies that comprise a robust directory data model. These artifacts are generally loosely constrained; additional conformance expectations and constraints are provided in other sections of the IG.
• National Directory API - constrains the Base artifacts and defines a FHIR API for accessing data from a national directory. Describes additional capabilities a national directory could implement, including subscriptions and bulk data export.
• National Directory Attestation - provides guidance describing the processes by which data is contributed to a national directory from individuals and organizations.
• National Directory Verification - provides guidance describing the processes by which attested data is verified for truthfulness and accuracy.
• Local Directory API - constrains the Base artifacts and defines a suite of optional capability statements describing APIs for various use cases local directories may support. Local directories may declare conformance to one or more of these capability statements.