Agreed, the language is confusing, especially because it uses uppercase Parameters, implying that each type would be represented with a separate instance of a Parameters resource, but the intent is a lower case "parameter", because what's being described is how to represent the type of parameters and expression definitions in a Library, so the "name" of the parameter element is the name of the parameter or expression definition, respectively. We will change the language to: Tuple types are represented in FHIR as a `parameter` that has parts corresponding to the elements of the tuple types and List types are represented in FHIR as a `parameter` that has a cardinality of 0..* In addition, we will provide an example illustrating the mapping for tuple and list types, including nested tuple and list types. And we note that for nested list types, the question about the name still arises, so we will indicate that the name of a nested list type parameter SHALL be `element` In addition, we will provide as part of that example an illustration of providing an empty list as a parameter, specifically using a new "isEmptyList" extension: { "name" : "Empty List-Valued Expression" , "_valueString" : { "extension" : [{ "url" : "http: //hl7.org/fhir/StructureDefinition/cqf-isEmptyList" , "valueBoolean" : " true " }] } } cqf-isEmptyList 0..1 boolean, fixed value to true (i.e. can never use this extension to say this is not an empty list)