Hi,

I know that this is probably something very inappropriate but I happened 
to need such a solution. An example:

CLUSTER [AAAA]
    CLUSTER [BBBB]   Some type of finding (a lesion: ulcers)
          ELEMENT [CCCC]   A Feature of the finding (i.e. bleeding)
                v: some value
          ELEMENT [DDDD]  Another Feature of the finding (area)
                v: some value
    ELEMENT [DDDD]   Another type of finding   (a lesion: atrophy)
                v: some value  OR null_flavor

My problem is I want to be able to state whether CLUSTER[BBBB] is 
observed (True) or not (False) when both features (ELEMENTs CCCC and 
DDDD) are not present (NULL). I am perfectly able to state it when the 
data structure is an ELEMENT.

Problem arises when none of the features (attributes) of CLUSTER [BBBB] 
is observed and that two things can happen:
1) None of the features could really not be assessed, but there is 
definitely an ulcer (presence=TRUE)
2) The lesion in CLUSTER [BBBB] is not visualized at all 
(Presence=FALSE). But then we need to know why (classical flavors of null)?

Of course a straightforward solution is putting under each CLUSTER with 
child nodes, a new ELEMENT describing its "presence" with Boolean type 
and with null_flavor.

However if it will not break very badly current semantics and other 
strategies, the advantages of such approach might be:
1) Reducing size, manageability and understandability of (big) archetypes
2) During querying of leaf-nodes in a huge repository, the search 
algorithm can first check parent nodes' presence and then further go 
down to leaf-nodes. If a whole branch is not valid/null from the top, 
then there is no need to look for lower levels and the performance might 
be enhanced.

I might be making a horrible proposal here technically or even there 
exists another solution already, but this is what I need.

Best regards,

Koray Atala, M.D.
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