Support Clinical Finding pattern in RM (negation / absence / presence)

We talked about this on multiple occasions...Certain kinds of data have peculiarities about depicting absence. Majority of examples I am aware of pertain to reporting of clinical findings. Simple example would be presence of rash. We can talk about its:
a) presence
b) absence
c) positive statement that it is unknown (for whatever reason). I think currently captured by null_flavour on ELEMENT)

We don't have the means to depict absence and hence modellers are either using dedicated data items to capture this causing a lot of repetition and clutter. A related issue happens at Archetype-instance level with the need to use specific EXCLUSION archetypes. While I understand this offers additional capability to capture additional data why data are absent I think the fact that data are absent should be found in the model that describes it and more importantly easily reachable. Currently the only means is to query for existence of these Exclusion archetypes which can be computationally costly.

So in a RM attuned for healthcare data one should expect to capture this at a more basic level - RM!. Essentially I'm talking about things you can talk about their absence. Not all data are like this - for example you cannot talk about absence of a procedure or tumour-grade etc.

My proposal is two-fold:
1) to add an optional Boolean flag to depict absence to ELEMENT Class
2) to add an optional Boolean flag to depict absence of an ENTRY; e.g. Problem/Diagnosis. Note that we can still continue to capture additional data using exclusion archetypes but I think semantically an Entry capturing data about an Observation or Evaluation should include data about its positive absence. In practice in very little cases those exclusion archetype data items will be used.

I think (2) needs further thinking...I think CIMI has this notion of design patterns and clinical finding is one of them - not sure how they handle this though...Tom?