is_integral attribute for DV_PROPORTION

Archetype editor uses the attribute is_integral for DV_PROPORTION, but there is not an equivalent RM attribute.
Should it be considered as a contraint on precision RM attribute (when is_integral=true --> precision=0)?
Anf when is_integral is false, this means precision should be>= 1? or whatever?
Why is not a precision attribute used?

Thank you.
Regards

leo