FHIR Chat · FHIRPath SDC example

Stream: questionnaire

Topic: FHIRPath SDC example

Tilo Christ (Aug 29 2021 at 07:36):

I am working with @Grey Faulkenberry to implement FHIRPath support into a questionnaire filler. I am trying to get the following SDC example to work: http://build.fhir.org/ig/HL7/sdc/examples.html#using-enablewhen-enablebehavior-and-enablewhenexpression . I have 2 questions:

am I right in assuming that "repeats" is a typo and it should be repeat (no trailing s)?
is there any kind of implicit / polymorphism etc. specified behavior that should allow "answer.toString()" to work as in the example, or should it be "answer.valueDate.toString()"?

I am essentially trying to understand whether our code is broken, or the example is incorrect.

Jose Costa Teixeira (Aug 29 2021 at 08:05):

which repeats would be a typo?

Jose Costa Teixeira (Aug 29 2021 at 08:13):

the one in expression seems a typo indeed

Tilo Christ (Aug 29 2021 at 09:26):

I am referring to this overall expression "expression": "%resource.repeats(item).where(linkId='4.2.b.1').answer.valueCoding.code ='female' and today().toString().substring(0, 4).toInteger() - %resource.repeats(item).where(linkId='4.2.b.5').answer.toString().substring(0, 4).toInteger() >= 40"
It has repeats(item) in it two times.

My second question is referring to the second half of the example where it says .answer.toString().

Jose Costa Teixeira (Aug 29 2021 at 10:32):

I think you are correct in assuming there are 2 issues with the documentation.
I don't know about the implicit casting, and I don0t find it in FHIRPath. The repeats seems a typo. I think the expression should be

%resource.repeat(item).where(linkId='4.2.b.1').answer.valueCoding.code ='female'
and (today().toString().substring(0, 4).toInteger() - %resource.repeat(item).where(linkId='4.2.b.5').answer.valueDate.toString().substring(0, 4).toInteger() >= 40)

Jose Costa Teixeira (Aug 29 2021 at 11:03):

Can others confirm please?
repeats does not exist in fhirpath, should be repeat. And answer.toString does not resolve, should be answer.valueDate.toString

Brian Postlethwaite (Aug 29 2021 at 11:21):

answer.valueString is not correct either, it is answer.value

Brian Postlethwaite (Aug 29 2021 at 11:22):

And you can add .toString() to that also.

Brian Postlethwaite (Aug 29 2021 at 11:24):

Check the fhirpath spec for how polymorphic types are defined here
http://hl7.org/fhirpath/#paths-and-polymorphic-items

Tilo Christ (Aug 29 2021 at 15:06):

so from this very compact spec, am I right in assuming that only the field name as specified for the choice is valid (if the FHIR spec says fieldname[x], then I can only use .fieldname, but not .fieldnameString? So the fully correct example would be %resource.repeat(item).where(linkId='4.2.b.1').answer.value.code ='female' and today().toString().substring(0, 4).toInteger() - %resource.repeat(item).where(linkId='4.2.b.5').answer.value.toString().substring(0, 4).toInteger() >= 40?

Jose Costa Teixeira (Aug 29 2021 at 15:17):

both resolve (according to https://hl7.github.io/fhirpath.js/):
answer.value and answer.valueDate.toString()

Tilo Christ (Aug 29 2021 at 15:25):

But I am wondering whether the latter "valueDate" is merely a side-effect of the JavaScript/JSON based implementation, or should really resolve according to spec.

Lloyd McKenzie (Aug 29 2021 at 16:08):

valueDate used to be allowed. It's not officially allowed any longer, though some of the tool stacks still support it. Can you submit a change request for us to fix the SDC example?