The top level logical operator in the current measures is ALWAYS an AND. In this case, nested under that is an OR. However, in the QDM logic, logical operators are always amongst 'siblings'. In this case the OR: clause has no siblings, so its results is simply the result of ANDing of the two clauses that lie underneath. the AND NOT clause is redundant with the numerator -- if an episode of care reaches the denominator exceptions population calculation, the NOT of the numerator condition is guaranteed to be true. THus, the only part of the denominator exceptions that does anything is the final AND. Sigh. Short version: the OR can be ignored, as can the AND NOT clause.