Existing Wording: Unrecognized search criteria SHALL always be ignored. (Search criteria supported in a query are echoed as part of the search response so there is no risk in ignoring unexpected search criteria.)

Comment:

I suggest striking or softening the statement about "no risk." This statement may not always be true, since it depends on what the impact of the unrecognized criteria would be. It might be obvious but it might be subtle. For example, if there is a query on the Patient Resource that intended to include patient ID and several other search criteria, but patient ID was erroneously submitted, might that search return unintended patients who matched the other search parameters?