Stream: cql
Topic: Retrieve with Codes Equality Semantics
Alexander Kiel (Dec 03 2019 at 19:14):
The equivalent (~) operation compares codes only by system and code ignoring the version, were the equal (=) operation also compares for version. What equality semantics are used in retrieves with codes - equal or equivalent?
Lloyd McKenzie (Dec 03 2019 at 19:55):
@Bryn Rhodes
Chris Moesel (Dec 03 2019 at 20:07):
@Alexander Kiel -- I suppose the spec doesn't make it 100% clear, but I believe that retrieves are intended to use equivalence. The behavior of a retrieve using a valueset is the same as using the In (ValueSet) function, which specifies that equivalence is used for codes and concepts (doc). And while it's just a passing reference, section 2.2 also states (when referring to an example):
The "Get Condition from Code Declaration" expression returns conditions for the patient where the code is equivalent to the "Acute Pharyngitis Code" code.
Bryn Rhodes (Dec 03 2019 at 20:55):
Yes, it's implied, but you're right, never explicitly stated. I've submitted an STU comment to clarify this in the specification, as the intent is definitely to use equivalence semantics (and at least the Java-based engine does that currently).
Bryn Rhodes (Dec 03 2019 at 20:55):
http://www.hl7.org/dstucomments/showdetail_comment.cfm?commentid=1882
Alexander Kiel (Dec 03 2019 at 20:55):
@Chris Moesel Thanks. I also checked FhirDataProviderR4 and it also doesn't use the version. In addition to that, FHIR token search also doesn't support version.
Ah thanks @Bryn Rhodes I see you comment while writing this. :-)
Last updated: Apr 12 2022 at 19:14 UTC
