PQS SI system semantics

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Semantics of operations on quantities in PQS SI system

Tthe SI system strongly favours normative units over unit conversions.

The SI system classifies units into si units and non-si units , which The PQS implementation classifies as normative_units and unit_conversions.¹ .

PQS makes use of the distinction between normative and unit conversions in its semantics of operations for its si system implementation. Binary operations are designed to favour normative units over unit conversions and in particular a unit_conversion may be converted to a normative_unit automatically in a binary operation. This reflects the spirit and purpose of the SI that "Only SI units and those units recognized for use with the SI are used to express the values of quantities" ²

Notes

• [1] Note that both quantities with si units and quantities with non si units can be modelled in the SI system
• [2] https://www.nist.gov/pml/special-publication-811/nist-guide-si-check-list-reviewing-manuscripts