Thomas,
All are Units of a different kind.
SI defines: Units of Measure, and Units of Quantity in the scientific domain.
There are also Units of Time: minute, hour, etc.
When I think of tablets, capsule, etc. we will call these Units of Medicinal
Product Dose.
Isn’t in UCUM this an example of Arbitrary Units?
<>3.2
ARBITRARY UNITS
<>§24 arbitrary units ■1 Arbitrary or procedure defined units are units
whose meaning entirely depends on the measurement procedure (assay). These
units have no general meaning in relation with any other unit in the SI.
Therefore those arbitrary semantic entities are called arbitrary units, as
opposed to proper units. The set of arbitrary units is denoted A, where A∩ U =
{}. ■2 An arbitrary unit has no further definition in the semantic framework
of The Unified Code for Units of Measure ■3 Arbitrary units are not “of any
specific dimension” and are not “commensurable with” any other unit.
Until version 1.6 The Unified Code for Units of Measure has dealt with
arbitrary units as dimensionless, but as an effect the semantics of The Unified
Code for Units of Measure made all arbitrary units commensurable. Since version
1.7 of The Unified Code for Units of Measure it is no longer possible to
convert or compare arbitrary units with any other arbitrary unit.
<>§25 operations on arbitrary units ■1 Any term involving arbitrary
units, is itself an arbitrary unit and is not comparable with any other
arbitrary unit or term.
<>§26 definition of arbitrary units ■1 Arbitrary units are marked in the
definition tables for unit atoms by a bullet (‘•’) in the column titled “value”
and a bullet in the column titled “definition”.
Gerard Freriks
+31 620347088
gf...@luna.nl <mailto:gf...@luna.nl>
> On 18 mei 2016, at 13:41, Thomas Beale <thomas.be...@openehr.org> wrote:
>
>
> On 18/05/2016 12:21, Grahame Grieve wrote:
>> The main problem is that ucum units are not human readable units,
>
> right - my idea 13 years ago was to use the UCUM string as a key into
> something that generated a human-readable form. For reasons that became
> clearer since, I think we all agree that we need to embed not just the formal
> form, but the human-readable form as well. So that's a fairly anodyne design
> problem for the Quantity type in everyone's type system. I think we can solve
> that in a reasonable way in openEHR.
>
>> and trying to force them to be will generate substantial pushback from end
>> users. In USA, this is an open problem for CDA adoption. In Australia, I
>> solved it by declaring that we would never retire valid ucum units in CDA.
>>
>> A secondary problem is discrete units like tablet, capsule etc which have no
>> computable form in ucum
>
> I suspect this is the main problem for some people at least these days.
> Scientifically speaking, anything like 'tablet', 'capsule', 'drop' etc isn't
> a 'unit' in the science/physics sense; but in English (and most other
> languages I suspect) we use the same word in a non-science sense to mean
> 'discrete amount of anything', e.g. unit shares, 5mg tablet is the unit of
> dosing, and so on. This makes people think the problem can be solved within
> the model / language of scientific units. It can't in any clean way.
>
> So dose 'units' need to be understood as something different from scientific
> units, and modelled in a different way. They are units of discretisation or
> quantisation of material, not units of physical properties.
>
> - thomas
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