Fwd: Question about decimal precision

FYI

-------- Forwarded Message --------
Subject:  Question about decimal precision
Date:  Fri, 24 Jul 2015 16:23:18 +1000
From:  Grahame Grieve <grahame@healthintersections.com.au>
Reply-To:  Grahame Grieve <grahame@healthintersections.com.au>
To:  HL7 ITS <its@lists.hl7.org>



Hi All

We've got a task submitted against FHIR here:
http://gforge.hl7.org/gf/project/fhir/tracker/?action=TrackerItemEdit&tracker_item_id=8175&start=0

The definition of xsd:decimal
(http://www.w3.org/TR/xmlschema-2/#decimal for v1.0,
http://www.w3.org/TR/xmlschema11-2/#decimal for v1.1), explicitly
precludes implied precision:

"Precision is not reflected in this value space; the number 2.0 is not
distinct from the number 2.00."


This is not consistent with what we say about the data type in the FHIR
data types page:
The precision of the decimal value is signficant (e.g 0.010 is regarded
as different to 0.01)

According to the commenter, we would have use xsd:string or
xsd:precisoinDecimal from xsd v1.1. Or change the way we do precision

I don't want to do any of these
- using xsd:string would be a big loss for schema generation tools
- using xsd 1.1 would be weird, given our stated policy for supporting tools
- changing the way we do precision would be a problem with regard to the
other specifications (and with regard to JSON too)

My inclination is actually to document this as a deviance from schema. I
think this is actually ok because we've been running this same deviance
for more than a decade in the v3 space, and not once I have heard about
this being a problem anywhere (and I've heard a lot about schema
problems in the v3 space). And nor in all the work we've done with FHIR
so far either.

So I really think that this is a theoretical concern, and that we just
add another text note to the precision notes about this issue

Grahame



-- 
-----
http://www.healthintersections.com.au /
grahame@healthintersections.com.au
<mailto:grahame@healthintersections.com.au> / +61 411 867 065

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Received on Tuesday, 28 July 2015 07:31:39 UTC