# Representing a Real value in openEHR

**Category:** [Clinical (archive)](https://discourse.openehr.org/c/clinical-archive/153)
**Created:** 2015-03-17 10:09 UTC
**Views:** 1
**Replies:** 11
**URL:** https://discourse.openehr.org/t/representing-a-real-value-in-openehr/14116

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## Post #1 by @system

Hello,

It might seem a very basic question, but I couldn't find an appropriate answer anywhere. Which is the best way to model a single Real number in openEHR? For example, a result of a score.

I have found two possible options:

- Use a DV_QUANTITY, with the "Qualified Real" property, that sets the units to an empty String. This approach is used in the "Harris Hip Score" archetype ([http://www.openehr.org/ckm/#showArchetype_1013.1.1873](http://www.openehr.org/ckm/#showArchetype_1013.1.1873))

- Use a DV_PROPORTION, with the PROPORTION_KIND set to Unitary. This approach is used in the "Waist and hip circumference" archetype ([http://www.openehr.org/ckm/#showArchetype_1013.1.332](http://www.openehr.org/ckm/#showArchetype_1013.1.332))

In both cases, it seems we are forcing to use a data type that does not really fit for purpose. Why don't we have something similar as the DV_COUNT, but representing a real number and not an integer? Something equivalent to the REAL data type in ISO 21090

David

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## Post #2 by @system

Hi David,

Qualified Real is the current preferred option (for me anyway). I think we have flagged up in the spec CRs that proper support for Real would be helpful as Qualified real is somewhat obscure.

So - agree with your request.

Ian

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## Post #3 by @thomas.beale

Hi David,

until we discovered that a few scores use non Integral values, there was no need for a 'real' type with no units\. There is a CR to enable DV\_ORDINAL to have real values\. Until then, I would suggest using the DV\_QUANTITY approach, that's the most frequently used one in the past\. Other than these scores, I have never heard of a real value that doesn't have units in medicine\. Does anyone know of any? If there is one, we would need a new data type as well, but it still wouldn't be the one to use for scores\.

\- thomas

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## Post #4 by @system

Well, as the openEHR data types specification document says, think of an archetype representing some statistical values such a covariance.

It is clear that the DV_QUANTITY is the most appropriate solution right now, but does not seem safe to rely on setting an empty unit to represent just a Real number

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## Post #5 by @yampeku

Qualified Real is a property from the domain type, not the type
itself, I thought the idea was to get rid of domain types in the
future\.

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## Post #6 by @thomas.beale

yes, I agree. Release 1.0.3 is coming soon ;-) - thomas

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## Post #7 by @Daniel_Karlsson

Hi,
what about the unit 1 \(uno\) for dimensionless quantities?
http://goldbook.iupac.org/D01742.html

/Daniel

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## Post #8 by @thomas.beale

is interesting - what they consider to be the dimensionless quantities. - thomas

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## Post #9 by @yampeku

So it would be stored as \{1\}? \(as they are supposed to be UCUM\)\. Empty
units doesn't feel like valid UCUM units either\.

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## Post #10 by @system

That's true Daniel, to be completely compliant with UCUM it seems the unit should be defined as 1 and not as an empty string.

[http://unitsofmeasure.org/ucum.html#section-Examples-for-some-Non-Units](http://unitsofmeasure.org/ucum.html#section-Examples-for-some-Non-Units).

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## Post #11 by @yampeku

True, UCUM is an obscure standard :D

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## Post #12 by @Daniel_Karlsson

I'm not an UCUM expert, but that's what I believe it should be\. Anything
with curlies seems to be equivalent to 1, so \{1\}=1\.

There is some more information under §29:
http://unitsofmeasure.org/ucum.html#section-Derived-Unit-Atoms
and there is a UCUM tracker issue:
http://unitsofmeasure.org/trac/ticket/2

/Daniel

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**Canonical:** https://discourse.openehr.org/t/representing-a-real-value-in-openehr/14116
**Original content:** https://discourse.openehr.org/t/representing-a-real-value-in-openehr/14116