Very weak request: The definition on search page, token, for when searcing for "|[code]" indicates that you are searching for the code ", and the Coding/Identifier has no system property." This seems to say that I am looking for the code value and an explicitly empty system value. This seems unusual need, but I guess it is useful. However there are cases, especially where federated backends exist, where the various backends have not used the same enforcing rules for system, that it might be useful to look for a code regardless of system. For example LOINC codes are sufficiently unique much of the time, while variations exist for the system value for LOINC codes. Yes, the FHIR spec is trying to drive exactly one string for the system value for LOINC codes... It seems just as useful to search for null system as it is search for any system.