Cumulative Medication Duration has been discussed in the QDM user group and the interim solution implemented in the most recent version (v4.1) takes a different expression than the way it is depicted above ( please read QDM-16 for solution details and the rationale behind it). The benefits of this interim solution are:  1.It fixes the existing syntax issue without reducing the original functionality  2.It's expressible in QDM syntax now  3.It's expressible in HQMF R2 now The limitations of this solution are:  1.You cannot "prorate" the CMD of medication events that overlap your period of interest. Whatever events are captured by your timing logic will contribute their CMD for the whole event to the aggregate calculation. In other words, if you compute the CMD over the 114 day period, it will include them in the computation rather than prorate it to the end of the 90 day MP. 2.Patient-reported medications will not be represented in the calculation (this was also a limitation of the last solution)  3.You cannot group medications using different value sets together (e.g., using a union) and get CMD for the whole group. Each CMD calculation is limited to the set of events represented by one QDM element with one value set.