2c389a02__Specifications___openEHR_wiki__openEHR_equivalent
[0] 4 [Code mnemonic] NINF [Rubric] negative infinity [Description] Negative infinity of numbers. [openEHR equivalent] 
Modelled in Interval and DV_INTERVAL classes. Note: this concept has nothing to do with null flavours or missing data. Respectfully, I disagree: you have a special boolean flag that says that the data is missing, and assigns an interpretation of that fact. I'm not saying that the HL7 nullFlavor is the right way to model it, just pointing out that it is to do with missing data
Null Flavours and Boolean data in openEHR - Specifications - openEHR wiki
openEHR equivalent