Active is a state of the diagnosis that is time dependent. All diagnoses have a start time, usually they begin as active. They usually remain active until they become inactive. This state of inactivity is commonly called resolved, so let�s consider the two states of active and resolved. To say a diagnosis is active raises the question of what point in time we are to evaluate its active status. If the specs say �Diagnosis active: X� starts before or during �instant Y�, consider the following scenarios. At a point Z, which is Y+180 days, I run the measure logic and see the following 1. A diagnosis that is active from (Y-60 days) to (Y-30 days). This diagnosis is not active at Z , and was not active at Y, but was active prior to Y. 2.A diagnosis that is active from (Y-60 days) to (Y+10 days). This diagnosis is not active at Z, and was active at Y, and prior to Y. 3. A diagnosis that is active from (Y-60 days) and has never been inactive. The diagnosis is active at Z, and was active at Y, and prior to Y. Consider the criterion �Diagnosis active: X� starts before or during �instant Y�.� Clearly we can�t look at the status of the diagnosis at Z, because Z is variable and has no clinical significance.� But the only requirement of the criterion is that it be active at some time before Y, there is nothing it says that it be active at Y. So we are left with a diagnosis that was active at any time before Y, and all 3 of the above are included. But logically this doesn't work, because active is really just an attribute of diagnosis and active diagnosis should not be a datatype. Instead, the QDM should have a diagnosis datatype, with attributes �Active start datetime�,�Active stop datetime�,�Resolved start datetime�, Resolved start datetime. Fundamentally, all datatypes should be fixed, a record should not be able to change from one datatype to another by a change in status. If we assume that the language above means a diagnosis that was active any time in the past and is of any status now, this problem arises: Currently, some measure authors use this criterion when they want to indicate �any past or present diagnosis�, but most seem to use it when they want to indicate �any diagnosis active during the measurement period�.� But it cannot mean both.