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Development of IFC 4.4
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Are we using measure_with_unit appropriately to track dimensional exponents? #1

Open Moult opened 2 years ago

Moult commented 2 years ago

Also agree that your interpretation is correct. The key documentation is under the ValueComponent:

The value of the physical quantity when expressed in the specified units.

One more thing I'd raise (which can be dealt with in a separate bug) is whether or not the IFCTHERMODYNAMICTEMPERATUREMEASURE is appropriate. Especially if we start to keep track of dimensional exponents. I hunted down the original 10303-41 and here is the documentation for measure_with_unit:

https://steptools.com/stds/smrl/data/resource_docs/fundamentals_of_product_description_and_support/sys/19_schema.htm#measure_schema.measure_with_unit

Then, if you check under value_component and click on measure_value, you get this list:

https://steptools.com/stds/smrl/data/resource_docs/fundamentals_of_product_description_and_support/sys/19_schema.htm#measure_schema.measure_value

Notice how there is this suggestion under numeric measure:

19.3.28 numeric_measure EXPRESS-G A numeric_measure is the numeric value of a physical quantity.

NOTE In order to define measure quantities that are not included as specific types in this standard a numeric_measure may be used as the value_component of a measure_with_unit, the corresponding unit_component being an si_unit or a derived_unit.

Perhaps we should've been using numeric measure all this time?

Originally posted by @Moult in https://github.com/buildingSMART/IFC4.3.x-development/issues/7#issuecomment-1006113788

Moult commented 2 years ago

Marking as onhold since this is a big issue.