XBRL 2.1 standard and the unit type registry (Unit Type Registry (xbrl.org))
Existing entries in the registry should be used where possible and there is an open process for adding new entries where necessary.
Example
Companies may report their breakdown of renewable and non-renewable energy usage either as a percentage of the total or an absolute amount in an energy unit. For example, one company (CarMaker) may report using both mechanisms:
Whereas a different company (Cloudify) may just report using one mechanism (percentages):
And a third company (OutSourcery) may report using the other mechanism (absolute values):
A taxonomy could constrain which variant is used but that might prevent some participants reporting in the way most natural to them. Alternately, one can unify all the above during analysis, by calculating derived values where they are missing, as seen below:
Links
·Comparing Absolute and Percentage Values (using Tableau)