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Status Declined
Product AVEVA™ PI Server
Categories Asset Framework (AF)
Created by Kenneth Barber
Created on Aug 19, 2022

RELATED IDEAS

Use "whole" as the canonical UOM of the Ratio UOM class

The Ratio UOM class represents part-to-whole ratios (i.e. the units are relative to the whole). Also, ratios are the result of a division. The division produces the number of wholes that the part represents. Any other ratio unit (e.g. %) requires scaling this division by some factor. Currently, the canonical UOM of the Ratio UOM class is %, which makes it awkward to define other units, especially those that are not based on powers of 10. For these reasons, the canonical UOM of the Ratio UOM class should be the "whole".
  • ADMIN RESPONSE
    Aug 19, 2022
    When defining the UOM's shipped with AF, whenever it makes sense, we use the 7 base units of SI. In the case of ratio, it different in that it's not a SI unit. If you consider ratio as being: "the quantitative relation between two amounts showing the number of times one value contains or is contained within the other," then one can argue % is appropriate. Given there is no SI standard for ratio and changing the canonical unit would break backwards compatibility, there is currently no overwhelming reason to make this change.
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  • Guest
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    |     Aug 19, 2022
    I think this does make sense to have a simple conversion between a ration 0-1 to percent 0-100 But nothing beyond that. Ratio is a oddity in any sense. Diving into this: https://en.wikipedia.org/wiki/Parts-per_notation shows that these "unitless" quantities share the same base, but still cannot be converted into each other. E.g. mm per meter cannot be converted into ppm, while both are ratios. So i'm not in favor of extending the ratio class. If needed, different ratio classes can be added. And even the ppm and ppb don't really belong there in my opinion.