We are trying to finish up HQMF Release 2.0 this week, seven of us, meeting in MITRE's offices in Bedford, MA. Initially this meeting was scheduled so that we could complete the big push to get the standard out in time to be referenced in Meaningful Use stage 3. With CMS' announcement that Stage 3 will not come out this year, I don't see the need to rush, rather I'd like to get it done well.
One of the challenges we worked out today was how to combine and reuse different criteria. We worked out a fairly elegant solution that allows a data criterion to be further refined, or be used with other criteria in union and/or intersection operations. We also worked out some simplifications around excerpts, realizing that we could just limit ourselves to FIRST, LAST, MIN and MAX and use that to be able to support Nth, or Nth from the end, without having to support the entire value set possible.
There are a few other simplifications in the works, and the combine and reuse solution also seems to allow us to address what I had quickly relabeled the 7 of 9 problem. The problem is that some measure developers want to be able to create numerator or denominator criteria where what is being counted meets N out of M other criteria. This is a pattern than is often used in certain kinds of assessment instruments, and rather than using an assessment result, you could just compute it based on the known data. Using the combination solution, there's a way we can say that.