All value sets have one or more definition versions, and each definition version for a value set has one or more expansion versions.

Value Set Definitions

Value set definitions include characteristics that an author uses to describe a value set. The extensional value set definition includes the author’s enumeration of terminology codes defined by the value set. The intensional value set definition enables authors to intensionally define value set terminology code content as a logical statement (e.g., all codes that are descendants of this code). Value set definitions exist only in the VSAC Authoring Tool. Value set metadata, which are part of the overall value set and not linked to the value set definition, include the following elements: value set name, value set OID, note, purpose statements, author group, and steward group.

Value Set Expansion

Value set expansions are computed by VSAC algorithms from each value set definition, created by authors in the VSAC Authoring Tool, using an author-designated expansion profile calculation of specified code system versions. The "Most Recent Code System Version in VSAC" expansion profile calculation consists of the most recent code system versions available in VSAC.

Value set expansions are snapshots-in-time of value set definitions computed by VSAC using author-specified expansion profiles or code system versions. Value set expansions exist only in the “Search Value Sets” tab (the public repository). VSAC will calculate value set expansions using the value set definitions chosen by the author or steward.

Expansion Profile Examples

Most Recent Code System Versions in VSAC - This is the default expansion profile used by VSAC. VSAC will publish a snapshot/temporary expansion, called Latest, of definition version named YYYYMMDD, at midnight Eastern Time based on the most recent code system versions. VSAC will publish subsequent 'Latest' expansions when code systems update.

Most Recent Code System Versions in VSAC with Codes in Active Status - Similar to "Most Recent Code System Versions in VSAC" but the "Legacy Codes" rule is set to "VSAC applied the most recent code system version that includes the code in an active status."

eCQM Update 2025-05-08 - Expansion profiles starting with "eCQM Update...." are expansion profiles for the eCQM Annual Update. This is an example of an expansion profile for the 2025 eCQM Annual Update. The legacy code rule is set to “VSAC applied the most recent code system version that includes the code in an active status.”

C-CDA R3.0 2024-08-09 - Expansion profiles starting with "C-CDA..." are expansion profiles for the C-CDA release. This is an example of an expansion profile for the C-CDA R3.0 2024-08-09 release. The legacy code rule is set to “VSAC applied the most recent code system version that includes the code in an active status.”

Steward Expansion - Designate a specific type of expansion for your value set, based on a later publication date, different code system version, or a pre-established expansion profile. Go to the Expansion/Publication tab in Authoring, and then select the Expand/Publish button.

Last Reviewed: July 3, 2025