One of the more controversial sessions at the Baltimore meeting was where we discussed task 10659: Reference should support logical references
This is a difficult subject because it relates to handling and exchanging information where a formal URL based view of the world is incomplete. In effect, that means, from a purist point of view, the world is already broken. This makes effective resolution difficult; at best, the resolution is also going to be broken – but is it broken in the least unuseful way? – that’s a bad place to try and get consensus from.
Further, in the FHIR framework, the Reference data type is clearly FMM level 5 – it’s been hammered everywhere from the beginning and is production in all sorts of places. And we’ve said that we won’t make breaking changes to FMM level 5 artefacts without consultation with the users. What’s not clear, though, is whether any of the changes that were proposed in the extensive discussion leading up to the quarter devoted to the task (see, for example, here and here) were actually breaking changes.
The outcome of the meeting was that we would add an Identifier to the Reference data type. Given the background, there was fairly strong consensus for the change, but it wasn’t complete. As a consequence, we said that we would define the change, let everyone look at it for a month, and see if any argument comes up that we had not considered.
So I’ve made the changes: see the Reference data type in the current build. Implementers are encouraged to evaluate the impact of this addition in their implementations, and share their findings on the FHIR email list.
Note: since this is not strictly a breaking change, this is not strictly consulting the implementers before making a breaking change 😉