MD_UnitOfMeasurement

Dimension

Unit of measurement used for a reading. Note that it is important to refactor measurements taken at different granularities so that they are compatible. So if all the units here are being regularly used, probably something is being done wrong. The fewer the better.

For example, we should not have entries here for PSI (lbs per square inch) and KPI (kilograms per square inch). The one unit should be converted into the other, particularly if the same thing is being measured. They can be converted back again in reports or crosstabs.

Some measurements may not have units, so it will be necessary to generate an 'Unknown' unit, to ensure that there is something in this table for every measurement.

No data type is available here (although source systems may have it) because they may choose to implement units to varying levels of precision. Here we want to consolidate everything into as few units as possible, and in the associated fact tables we'd like to jam everything into a single 'long float' data type, so we don't end up with type mismatches when aggregating.

Note that conversion factors are given here for various units. These COULD HAVE BEEN BROKEN OUT INTO A SEPARATE unit-to-unit conversion table and properly normalized. This WAS NOT DONE HERE because this table is largely static and is maintained by hand, and it's therefore easier to have a denormalized table with extra columns for each conversion, and simply leave them blank where they don't apply. The fact is that there is a small/finite set of units we want to convert to (feet, square feet, cubic feet, watts, BTUs, etc.), so we only need enough columns to handle those units.