It would be simpler and clearer to make
DV_QUANTITY.value a REAL (probably mapped to a DOUBLE)
rather than its current model of NUMERIC with 4
subtypes. THis will facilitate mapping in programming
languages. It will also map better to the HL7 type PQ.
Note however that floating point rounding errors are
very problematic when using doubles as the
representation for real numbers, so this should be