Stream: fhirpath
Topic: Ballot
Grahame Grieve (May 14 2018 at 07:24):
GF#17130 - we should dsicuss this here
Bryn Rhodes (May 14 2018 at 22:13):
The issue is that the CQL specification uses the Equivalent operator (~) to do membership testing and duplicate detection in all list operations, where the FHIRPath spec uses the Equal operator (=) for that purpose.
We do it this way in CQL so that null behavior doesn't bleed into list membership semantics, otherwise you'd never be able to tell if a row that had any null elements was in a list of rows. It's also done to match semantics of most SQL-based DBMSs in this regard.
However, FHIRPath is specifically defined to use Equal. It's admittedly less of an issue in FHIRPath because FHIRPath doesn't have nulls, but it will lead to some inconsistencies between CQL and FHIRPath unless we align.
So the proposal in the comment is to change FHIRPath membership testing and duplicate detection to use equivalent, rather than equal.
This would impact the following functions and operators:
subsetOf()
supersetOf()
isDistinct()
distinct()
intersect()
exclude()
union() (aka |)
in
contains
Specifically, { } in { } would now return false, where previously it would have returned an empty collection.
Bryn Rhodes (May 14 2018 at 22:28):
I've also added followups on GF#17131 and GF#17126.
Grahame Grieve (May 15 2018 at 03:09):
we use equals for a very good reason and we specifically discussed this in the past
Bryn Rhodes (May 15 2018 at 07:13):
Reconciliation now in ITS in 18
Bryn Rhodes (May 15 2018 at 08:07):
Discussing GF#17136, should we add a Date type to FHIRPath?
Grahame Grieve (May 15 2018 at 08:08):
I don't have a strong feeling
Michel Rutten (May 15 2018 at 08:12):
Maybe useful for inspiration/guideline: https://github.com/nodatime/nodatime
Bryn Rhodes (May 24 2018 at 22:42):
I've prepared proposed dispositions for GF#17130, GF#17128, GF#17136 and GF#17129. @Grahame Grieve @Ewout Kramer @Brian Postlethwaite @Chris Moesel @Michel Rutten
Lynn Laakso (Apr 29 2019 at 12:25):
Just a reminder that voting on the normative ballot ends today (FHIRPath is lagging behind our other normative ballots to reach quorum)
Last updated: Apr 12 2022 at 19:14 UTC
