FHIR Resource Search Token Namespace

Question

From the spec:

token Search parameter on a coded element or identifier. May be used to search through the text, displayname, code and code/codesystem (for codes) and label, system and key (for identifier). It's value is either a string or a pair of namespace and value, separated by a "!".

My question is on the last part. What does "namespace and value" refer to?

Something like use!usual (to search the "use" elements value attribute for the term "usual")?

Or more like urn:oid:1.2.36.146.595.217.0.1!12345 (to search the "key" elements value attribute for 12345 where the "system" elements value attribute is urn:oid:1.2.36.146.595.217.0.1)?

The latter was inferred from the XSD comment for the Identifier type (which is used as a token for Patient searches) "Establishes the namespace in which set of possible id values is unique".

What is the proper way to interpret a namespace inclusion on Token search fields?

Answer 1

The second:

"oid:1.2.36.146.595.217.0.1!12345" searches the "key" elements value attribute for 12345 where the "system" elements value attribute is "urn:oid:1.2.36.146.595.217.0.1"?

yes, that's how it works. note I clarified that the correct urn for an oid is the urn:oid: not just oid:

I will clarify in the spec.