Apologies, I suspect this may be due to my lack of knowledge of interpreting the reference model.
For an Observation archetype, I see the following on CKM
I don’t understand how something can be mandatory and have a minimum of ‘0 items’ (which sounds optional).
What am I missing here?
The cardinality statement refers to the ITEM_STRUCTURE inside protocol - cardinality in openehr refers to the number of items that can be carried in a container such as ITEM_TREE or CLUSTER.
For RM attributes, it is ‘existence’ which controls whether an attribute is optional or mandatory.
However protocol is optional in the parent CARE_ENTRY class, so I’m not clear why CKM is marking it as mandatory.
It is, but note the definition of existence in the specs: Existence
In particular:
The default existence constraint, if none is shown, is {1…1}.
This to me means that if you explicitly state protocol in the adl but do not state anything about its existence, it becomes mandatory, even though per se it is not.
If I remember correctly, we considered changing this or publishing an erratum for this a very long time ago, but then did not.
@sebastian.garde @ian.mcnicoll thank you both !
It would be good to revisit that ‘mandatory’ interpretation. It conflicts with the other rule which says that 'empty attributes should not be persisted in the EHR.
e.g. if the protocol tree is not populated then it should be omitted, even if a constraint is carried in the archetype and I believe that CDRs do obey that rule.
Yikes - ADL archeology!!
