We will update the rules describing FHIR-x-query ( expressions.html#fhirquery ) as follows: if the expression resolves to a complex element of type Coding, Identifier, or Reference, the element content will be substituted using the standard token format.   if the expression resolves to a complex element of type CodeableConcept, the processing will behave as though the expression had an additional node specifying ".coding".  i.e. the substitution will execute on the collection of codings resolved to within the CodeableConcept. if the expression resolves to an element of type Quantity, it will be converted to a search type of 'quantity' if the expression resolves to a collection of more than one value, the substitution will be a list of comma-separated values (i.e. behaving as 'or') Will also include an example showing how substitution would work searching based on the start and end values within a period element.