Currently the MUST SUPPORT statement indicates ".....When a profile does this, it SHALL also make clear exactly what kind of "support" is required, as this could involve expectations around what a system must store, display, allow data capture of, include in decision logic, pass on to other data consumers, etc."

While there is clearly variability across profiles and IGs what exactly would be included in MUST SUPPORT, there is at least one aspect that should be universally applied across all profiles that use MUST SUPPORT and that is that the API that makes the data available for a read must always populate the attribute marked as MUST SUPPORT when it has that data and a null flavor would not be sufficient. This sets a consistent expectation that data is always shared when marked MUST SUPPORT and when the source has that data. If that behavior cannot be required when an attribute is marked MUST SUPPORT, then the scope of that profile is not well defined.