# DV_PROPORTION vs DV_QUANTITY for % **Category:** [Technical (archive)](https://discourse.openehr.org/c/technical-archive/156) **Created:** 2019-01-03 06:58 UTC **Views:** 1 **Replies:** 14 **URL:** https://discourse.openehr.org/t/dv-proportion-vs-dv-quantity-for/14421 --- ## Post #1 by @siljelb Hi everyone, happy new year! We’ve just hit a question about modelling choices, how to represent percentages. We have a data type DV_PROPORTION, which can be used to represent any proportion such as a fraction or a percentage, and we have the DV_QUANTITY data type which can have % as the unit. In most existing archetypes such as the OBSERVATION.pulse_oximetry archetype, we’ve used the DV_PROPORTION data type for the percent elements, while for some reason in the draft EVALUATION.alcohol_consumption_summary archetype we’ve chosen DV_QUANTITY with the unit ‘%’ for the “Strength” element. We’ve had a look at the data types documentation ([https://specifications.openehr.org/releases/RM/latest/data_types.html](https://specifications.openehr.org/releases/RM/latest/data_types.html)), and we can’t really find any guidance in the examples there. Is there any guidance about this anywhere else? Does anyone have any opinions about when to use each data type for percentages? Kind regards, **Silje Ljosland Bakke** Information Architect, RN Coordinator, National Editorial Board for Archetypes Nasjonal IKT HF, Norway Tel. +47 40203298 Web: [http://arketyper.no](http://arketyper.no/) / Twitter: [@arketyper_no](https://twitter.com/arketyper_no) --- ## Post #2 by @system I think DV_QUANTITY is the option here. Someone could argue that % is not a proper unit, but it is, both in UCUM and SNOMED CT. DV_PROPORTION should be only used when you want to maintain the numerator and denominator explicitly separated, as a fraction, which should not be the case with percentages. But it is true that the definition of the type attribute in the specification is a bit misleading: "Indicates semantic type of proportion, including percent, unitary etc." --- ## Post #3 by @system David is right on all counts \- use DV\_QUANTITY, but we should fix that line in the specification\. Can someone raise a PR on that please\. \- thomas --- ## Post #4 by @siljelb In that case, I don't understand the use case for the 'percent' and 'unitary' variants of the DV\_PROPORTION data type\. What are they for? Regards, Silje --- ## Post #5 by @system Hi Silje, See [here](https://specifications.openehr.org/releases/RM/latest/data_types.html#_ratios_and_proportions). But I think the % case may have been there since early 2000s and either % was not in UCUM, or perhaps it was, but we did not realise it. So ideally we should change the documentation to obsolete it in DV_PROPORTION. - thomas --- ## Post #6 by @system There is a very clear use-case for having it there - O2 levels variably and equivalently described a FiO2 which is a unitary proportion or percent. I think we need to keep it for that reason if no other. Ian --- ## Post #7 by @system So in that case we need to upgrade the documentation for when to choose a DV\_QUANTITY percent, and when a DV\_PROPORTION %\. \- thomas --- ## Post #8 by @siljelb I think maybe actual modelling practice should be taken into account here\. Since these guidelines haven't been available, several important percentages in published archetypes have been modelled as DV\_PROPORTION: openEHR\-EHR\-CLUSTER\.inspired\_oxygen\.v1 https://ckm.openehr.org/ckm/#showArchetype_1013.1.393 openEHR\-EHR\-OBSERVATION\.pulse\_oximetry\.v1 https://ckm.openehr.org/ckm/#showArchetype_1013.1.3084 The way I understand the arguments here, there isn't a good one for changing these data types and going to v2 for these archetypes? Regards, Silje --- ## Post #9 by @system Hi Silje, As you say, I think this a case of emerging clarity (or less fog of confusion!!) as the various use-cases emerge. As the primary author of both these archetypes, in retrospect I would probably keep inspired_oxygen as DV_PROPORTION and change pulse_oximetry to DV_QUANTITY but!!! I do not see any good argument for changing these now. We have to expect some degree of inconsistency, and live with it, to avoid unnecessary breaking changes. Ian --- ## Post #10 by @system one thing to note: DV\_PROPORTION is a more complex data structure\. I would be tempted to try to determine what use has been made of this archetype so far \- i\.e\. in creating real data\. If no real data has been created, then it could in theory be changed\. \- thomas --- ## Post #11 by @system Simple answer - loads of real data - pulse_oximetry and Oxygen levels will have been recorded hundreds of thousands if not millions of times in patient data - and Proportion *is* the correct datatype for O2 levels. Ian --- ## Post #12 by @siljelb I still don’t understand if we have a conclusion. And I don’t understand why proportion is the correct data type for O2 levels but not for alcohol levels. Regards, **Silje** --- ## Post #13 by @siljelb Anyone…? 😊 --- ## Post #14 by @yampeku As far as I understand in oxygen levels the denominator is not 100 but a quantity, and that denominator may vary. I don't know how it is measured in alcohol, but probably % of alcohol in blood assuming always the same quantity to get the percentage? I'm not really sure anyway :) --- ## Post #15 by @system Sorry - the reason is that O2% is also described as FIO2 which is directly mathematically equivalent. FiO₂ Proportion Optional Fraction of oxygen in inspired air. Comment: For example: '0.28'. Unitary Numerator: 0.0..1.0 Percent O₂ Proportion Optional Percentage of oxygen in inspired air. Comment: For example: '24 %' Percent Numerator: 0.0..100.0 --- **Canonical:** https://discourse.openehr.org/t/dv-proportion-vs-dv-quantity-for/14421 **Original content:** https://discourse.openehr.org/t/dv-proportion-vs-dv-quantity-for/14421