Stream: fhirpath
Topic: FHIRPath Processor
Paul Lynch (Jul 18 2018 at 22:48):
I'm giving serious thought to writing an open source JavaScript FHIRPath processor (engine?). I am aware of the one https://github.com/jmandel/fhirpath.js, but was informed by Josh that that one is neither complete nor a good starting point. I was able to generate a working JavaScript parser from the ANTLR grammar, but before I get too far into what seems to be a big task that I probably don't fully understand, I would like to ask whether anyone else has worked on or is working on an open source JavaScript FHIRPath processor. If so, perhaps we could collaborate?
nicola (RIO/SS) (Jul 18 2018 at 22:50):
I hope, i will have time to help you with it - i promised David Hay sometimes to finish it :)
nicola (RIO/SS) (Jul 18 2018 at 22:50):
Year ago i did one in clojure
Chris Moesel (Jul 18 2018 at 22:55):
Given that fhirpath is a subset (of sorts) of CQL, it might be possible to leverage the cql-execution project, which is currently in CoffeeScript but published to npm as transpiled javascript. (We're also working on a port to ES6, but that's a little stalled right now.)
nicola (RIO/SS) (Jul 18 2018 at 22:56):
i would prefer to make it standalone
Chris Moesel (Jul 18 2018 at 22:58):
That said, there would be some effort involved there. Some things you'd want to be aware of:
1. It actually operates on the ELM JSON, so you'd still need the Java CQL-to-ELM translator -- which I think supports fhirpath? @Bryn Rhodes?
2. We don't have a FHIR STU3 (or R4) data binding yet -- although it would be fairly easy to update cql-exec-fhir to support it.
3. There might be some fhirpath operators that aren't implemented yet, as it's mainly been used w/ CQM and CDS use cases.
Chris Moesel (Jul 18 2018 at 22:58):
Ha. Yeah, with all of those caveats, I can understand if you'd like a smaller more focused implementation. But I thought I'd put it out there just in case.
nicola (RIO/SS) (Jul 18 2018 at 23:06):
FHIRpath implementation requires also some FHIR metadata, so i think we can provide this metadata not thro the code-generation, but directly as a data - so implementation will be version agnostic - less efforts to support.
Bryn Rhodes (Jul 18 2018 at 23:12):
@Chris Moesel , yes, the translator supports FHIRPath, and there are unit tests on the engine that flex that aspect.
Chris Moesel (Jul 18 2018 at 23:19):
Just to clarify: Regarding the unit tests, you're talking about the Java CQL engine. The CoffeeScript engine doesn't have unit tests for any fhirpath specific stuff. These guys are looking for a JavaScript implementation of fhirpath.
nicola (RIO/SS) (Jul 19 2018 at 00:19):
@Bryn Rhodes do we have good test cases for FHIRpath in JSON, covering most of specification?
nicola (RIO/SS) (Jul 19 2018 at 00:20):
Last time i was looking for test cases - they were only in XML :(
nicola (RIO/SS) (Jul 19 2018 at 00:21):
Ideally it can be just data like {resource: {....}, fhirpath: 'expression', result: value}
Grahame Grieve (Jul 19 2018 at 00:32):
good test data here:
Grahame Grieve (Jul 19 2018 at 00:33):
build\tests\resources\tests-fhir-r4.xml (in FHIR svn)
Grahame Grieve (Jul 19 2018 at 00:33):
tests themselves are in XML, but can be run on the json resources
Grahame Grieve (Jul 19 2018 at 00:34):
it's not that hard to read xml ;-)
Brian Postlethwaite (Jul 19 2018 at 00:34):
https://www.w3schools.com/xml/dom_intro.asp
if you really must do it from the JavaScript side.
Brian Postlethwaite (Jul 19 2018 at 00:34):
Its is only for testing afterall... :)
nicola (RIO/SS) (Jul 19 2018 at 00:35):
@Grahame Grieve why do not provide both xml & json versions like for other resources?
Grahame Grieve (Jul 19 2018 at 00:35):
because the tests are not a resource.
Grahame Grieve (Jul 19 2018 at 00:36):
they do nominate an xml file as input, but in no case is the outcome dependent on using the xml not the json as input
nicola (RIO/SS) (Jul 19 2018 at 00:38):
may be adopt https://www.hl7.org/fhir/testscript.html for that?
Grahame Grieve (Jul 19 2018 at 00:39):
maybe but it would be way overkill for what's a simple thing at the moment.
Grahame Grieve (Jul 19 2018 at 00:39):
just use an xml--> json translator on the fly ...
nicola (RIO/SS) (Jul 19 2018 at 00:39):
ok - but this is again JSON discrimination :)
Grahame Grieve (Jul 19 2018 at 00:40):
it's really simple: json doesn't have comments.
Grahame Grieve (Jul 19 2018 at 00:40):
like a car without doors
nicola (RIO/SS) (Jul 19 2018 at 00:41):
XML harassment: let's switch to yaml :)
nicola (RIO/SS) (Jul 19 2018 at 00:41):
it has comments
Brian Postlethwaite (Jul 19 2018 at 00:41):
Go plain text with pipe delimiters?
(kidding of course)
nicola (RIO/SS) (Jul 19 2018 at 00:43):
https://plus.google.com/+DouglasCrockfordEsq/posts/RK8qyGVaGSr
Grahame Grieve (Jul 19 2018 at 00:45):
yes he was wrong then and he's still wrong now. And JSMin is a javascript thing.
nicola (RIO/SS) (Jul 19 2018 at 00:46):
@Brian Postlethwaite no - next step is binary formats like protobuf, which go father then just pipe delimiters. And the whole IT industry is on JSON side - XML is dead.
Grahame Grieve (Jul 19 2018 at 00:48):
if we started using // for comments in JSON.... everyone not using javascript will need a new parser
nicola (RIO/SS) (Jul 19 2018 at 00:50):
nicola (RIO/SS) (Jul 19 2018 at 00:51):
https://stackoverflow.com/questions/10316997/how-can-i-read-json-with-comment-with-json-net
Grahame Grieve (Jul 19 2018 at 00:53):
I would also have to read the file with 2 other parsers
Paul Lynch (Jul 19 2018 at 20:21):
It should be easy enough to convert XML test cases to JSON,--or for that matter to parse the XML in JavaScript. I see the XML version at https://github.com/hl7-fhir/fhir-svn/blob/master/tests/resources/tests-fhir-r4.xml. It references a "patient-example.xml" which I don't see under tests/resources/. Where is that?
Bryn Rhodes (Jul 19 2018 at 20:25):
They are included here (at least for the STU2, looks like there ought to be STU3 and R4 versions included as well).
Grahame Grieve (Jul 19 2018 at 20:27):
those files are part of the FHIR Spec
Brian Postlethwaite (Jul 19 2018 at 21:58):
(therefore are available as both xml and json :) )
Last updated: Apr 12 2022 at 19:14 UTC
