When executed against a ValueSet, the $validate-code operation can take the valueSet to use for validation as a parameter to the operation, rather than against an existing value set already on the server. This is used a lot by the IG publisher, when using value sets defined in the IG being published, so that they don't need to be registered in advance on the server.

But what if a valueSet being passed to the server imports another valueSet not known on the server? This is a very common thing in IGs now. In order to evaluate the valueSet, the imported valueSet (and it's code systems and imported value sets recursively) are also needed. But right now, there's no way to pass them to the server. 

tx.fhir.org is using the parameter "tx-resource" to pass these to the server. Both the validator and the IG publisher use this parameter to include related value sets that the server will need to know.

Given that this is a challenge shared generally by any client passing value sets to the server on the fly, as already defined, we should formally document the tx-resource parameter 

Terminology servers should be encourage to pre-adopt this in earlier versions of FHIR