We will rework this section to respond to this ticket and another ticket ( https://jira.hl7.org/browse/FHIR-34723 ). We propose to adjust the opening paragraph of section 4.0.3 to the following: "For profiles defined in other IGs, the meaning of Must Support is established in the defining IG. Note that the Must Support requirements for this IG are modeled after the US Core implementation guide. The requirements for Health Plan API actors are modeled on those for US Core Responders, and the requirements for Consumer App actors is modeled on those for US Core Requestors. When querying and reading CARIN IG for Digital Insurance Card Profiles, Must Support on any profile data element SHALL be interpreted as follows:" Propose we remove the sentence: "NOTE: The above definition of Must Support is derived from HL7v2 concept Required but may be empty - RE described in HL7v2 V28_CH02B_Conformance.doc." to clear up any further confusion. HL7v2 is a much older standard.