Currently, the QDM HQMF IG does not always support a 1:1 mapping between QDM attributes and the corresponding XML output. Examples:

• Start datetime & Stop datetime must use the same effectiveTime instance for a QDM Datatype.
• Radiation Dosage & Radiation Duration must use the same instance of the Radiation Duration and Dosage supporting template.
• Facility Location, Facility Location Arrival Datetime & Facility Location Departure Datetime must all use the same location participant instance.

Based on analysis, the QDM IG really modeled these attributes as attributes of sub-datatypes, but sub-datatypes do not exist in QDM. An example:

Datatype: Encounter, Performed
Sub-datatype: EffectiveTime (attributes: start datetime; stop datetime)
Sub-datatype: Facility Location (attributes: type, arrival datetime, departure datetime)

Furthermore, measure observation expressions are really confined to using this type of approach. For example:

Encounter.effectiveTime.high - Encounter.effectiveTime.low

For various reasons (including but not limited to resolving issues described above), we recommend that QDM only allow one attribute to be applied to a QDM element for a single line of logic.