The current wording doesn't make it super clear how to specify deep chains - which won't be a simple 'code' for the target resource. Also, some people might think that they should specify the full string (e.g. "general-practitioner.partof.endpoint") or should lead with a "." (e.g. ".partof.endpoint")

Proposed Wording:

E.g. to specify support for chaining on the general-practitioner search parameter on Patient, a possible chain value might be "partof.endpoint" to allow a search of "general-practitioner.partof.endpoint"

(Comment 93 - imported by: Ron G. Parker)