EvidenceVariable is a very complex resource with 5 BackboneElement- and 3 CodableConcept- datatypes as well as recursive use of the characteristic backbone element.

The present documentation alone does not suffice to help users of this resource get started.

For one, the high level of context between elements in the resource is hardly described and the number of possible options provided by the resource make its use confusing...  EvidenceVariable.characteristic supports 3 approaches to characteristic definition:

• characteristic.definition[x]
• characteristic.defByTypeAndValue
• characteristic.defByCombination

Choosing between the 3 is not self explanatory and needs guidance. 

Also 

• linkId
• groupMeasure  

need better explanation.

Due to limitations of what can be put in description & constraints I suggest reworking scope and usage especially for explaining the 3 approaches to characteristic definition.

Alot of work on descriptions is being done in the run-up to the connectathon dealing with Eligibility Criteria but the right place for those descriptions is in the resource itself.  It would be great to have this improved before the connectathon.