Stream: terminology
Topic: 'exists' search modifier
Jack Bowie (Mar 15 2018 at 00:12):
In section 2.21.1.4.16 of the Searching description (v3.2.0), the modifier 'exists' is described. Yet this modifier is not present in the earlier discussion of modifiers. Rather, 'missing' is described and (kindof) similar. Is 'exists' a valid modifier?
Grahame Grieve (Mar 15 2018 at 00:33):
:exists was renamed to :missing in order to get the default correct. I think that I got all the references to it yesterday
Jack Bowie (Mar 15 2018 at 00:57):
Thanks. What default? Isn't true or false required?
Grahame Grieve (Mar 15 2018 at 00:59):
:exists had a default value of true - nasty. So :missing has a default of false, which is much less nasty
Jack Bowie (Mar 15 2018 at 01:10):
so parameter values , '=xxx', aren't required?
Grahame Grieve (Mar 15 2018 at 01:12):
empty parameters are ignored
Jack Bowie (Mar 15 2018 at 01:26):
Sorry, still confused. A parameter is 'name=value'. (Potentially with mod and/or prefix). Is it really 'name=[value]' with value optional? And defaults provide the default value, as in 'missing='?
Grahame Grieve (Mar 15 2018 at 01:29):
well, all http/html forms works the same: name1=value&name2= means that no value is supplied for name2, and you ignore it or process it with some default value
Grahame Grieve (Mar 15 2018 at 01:30):
we didn't like that the effective default value for :exists was true (even though you can just ignore it and not think in terms of a default value at all)
Jack Bowie (Mar 15 2018 at 01:34):
Okay. Default makes sense on 'missing'. This should probably get described somewhere. Do any other parameters have defaults (besides 'missing')?
Grahame Grieve (Mar 15 2018 at 01:58):
we are explicit about empty parameters: http://build.fhir.org/search.html#errors. We don't explicitly document the default value thing, since that's about how we operate rather then how implementers operate
Last updated: Apr 12 2022 at 19:14 UTC
