# Property

Every property in IFC has a data type and name and can have a definition explaining its meaning and a quantity kind defining a measure and a unit of storage.

## Data types

Every property in IFC has a data type. Allowed IFC data types are: 
- String, 
- Integer, 
- Real (double precision number), 
- Boolean (true/false), 
- Binary, 
- List (multiple values of the same data type).

- [ ] TODO List or Array? It could be an unknown size.
- [ ] TODO logical (true/false/unknown)?
- [ ] TODO what about empty values?

## Units and quantity kinds

The quantity kinds are useful to help interpret the property value and enable software to make automatic unit conversions.

All the data in IFC is stored using the default units for every quantity kind, such as metres for length. That helps to ensure consistency, precision, performance and interoperability across implementations. Software can display user-prefered units (read more: [display units](#display-units)).

## Measureless units

Many numeric properties require units that are not related to any defined quantity kind. In those cases, a basic data type Real/Integer should be used, with the unit specified in the property definition. 

For example:
- monetary units, like the euro (€/EUR) and US dollar ($/USD), depend on dynamic currency exchange rates, therefore in IFC should be treated as real numbers without a measure. 
- pixel (px), a unit of digital image resolution, has no physical size unless a resolution is specified, and in IFC should be treated as an integer, not a measurable length.
- kilobyte (kB), a unit of digital information storage equal to 1,024 binary bytes, in IFC should be treated as an integer.

## Derived units

Most common derived units are already included in [the table](#list-of-ifc-quantity-kinds). For example, "cubic metre per second" is derived from time and volume, which is derived from length. 

For all the missing derived units, we recommend following the same approach as with measureless units. If there are important quantity kinds missing you can suggest an improvement here: [IFC5 suggestions](https://github.com/buildingSMART/IFC5-development/discussions/categories/suggestions).

## Special units

Some properties require special units that are based on those defined in [the table](#list-of-ifc-quantity-kinds) but with additional meaning. That semantic meaning should be conveyed through property definition, and a basic quantity kind should be applied to allow for conversions. For example:
- the unit of global warming potential, "kilogram CO₂ equivalent" (kg CO₂ eq), should be defined as a mass quantity kind and stored in kilograms, with the meaning clarified in the definition. 
- "millimetre of mercury" (mmHg), despite the name suggesting it is a length quantity, should be represented as a pressure quantity in Pascals (1 mmHg = 133.322 Pa).

## Display units

Software can display IFC data in user-prefered units. The software needs to perform the conversion. The IFC does not specify the conversion factors or tolerance. The conversion typically involves:
- scaling (e.g. kilo = x1000, mili = x0.001)
- converting between metric and imperial systems (e.g. inch ➝ metre = x0.0254, pound ➝ kilogram = x2.2046226218)
- switching between units that are more applicable to context (e.g. litre ➝ cubic meters = *0.001, degree ➝ radians = π/180)
  
## List of IFC quantity kinds

- [ ] DECIDE: add measure for information? kilobyte? or SI unit for information - bit (8 bytes)? This would enable conversions kB, GB, TB...

| Original name                                 | Name                                    | QUDT quantity kind                  | Data Type |  Unit name                       |  Unit symbol        | QUDT unit           | Dimensional exponents   |  IFC4.3 unit enumeration                                   | IFC Base unit? | SI Base or derived unit? | InIFC2x3 | InIFC4 | InIFC4.3 | InIFC5 | Tier | Comment                                                                                                                         |
| --------------------------------------------- | --------------------------------------- | ----------------------------------- | --------- | -------------------------------- | ------------------- | ------------------- | ----------------------- | ---------------------------------------------------------- | -------------- | ------------------------ | -------- | ------ | -------- | ------ | ---- | ------------------------------------------------------------------------------------------------------------------------------- |
| IFCPLANEANGLEMEASURE                          | Plane angle                             | Angle                               | Real      | Degrees                          | °                   | DEG                 |                         | IFCUnitEnum.PLANEANGLEUNIT                                 | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 1    | Changed from radians to degrees. DECIDE rad or degrees.                                                                         |
| IFCTHERMODYNAMICTEMPERATUREMEASURE            | Thermodynamic temperature               | Temperature                         | Real      | Kelvin                           | °K                  | K                   | (0, 0, 0, 0, 1, 0, 0)   | IFCUnitEnum.THERMODYNAMICTEMPERATUREUNIT                   | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 1    | DECIDE kelvin or celcius (DEG_C).<br>DECIDE Temperature or Thermodynamic Temperature                                            |
| IFCELECTRICCURRENTMEASURE                     | Electric current                        | ElectricCurrent                     | Real      | Ampere                           | A                   | A                   | (0, 0, 0, 1, 0, 0, 0)   | IFCUnitEnum.ELECTRICCURRENTUNIT                            | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCTIMEMEASURE                                | Time                                    | Time                                | Real      | Second                           | s                   | SEC                 | (0, 0, 1, 0, 0, 0, 0)   | IFCUnitEnum.TIMEUNIT                                       | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCFREQUENCYMEASURE                           | Frequency                               | Frequency                           | Real      | Hertz                            | Hz                  | HZ                  | (0, 0, -1, 0, 0, 0, 0)  | IFCUnitEnum.FREQUENCYUNIT                                  | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCMASSMEASURE                                | Mass                                    | Mass                                | Real      | Kilogram                         | Kg                  | KiloGM              | (0, 1, 0, 0, 0, 0, 0)   | IFCUnitEnum.MASSUNIT                                       | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCLENGTHMEASURE                              | Length                                  | Length                              | Real      | Metre                            | m                   | M                   | (1, 0, 0, 0, 0, 0, 0)   | IFCUnitEnum.LENGTHUNIT                                     | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCLINEARVELOCITYMEASURE                      | Linear velocity                         | Velocity                            | Real      | Metre per second                 | m / s               | M-PER-SEC           | (1, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.LINEARVELOCITYUNIT                      | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ✔️     | 1    | DECIDE Speed or Linear velocity                                                                                                 |
| IFCFORCEMEASURE                               | Force                                   | Force                               | Real      | Newton                           | N                   | N                   | (1, 1, -2, 0, 0, 0, 0)  | IFCUnitEnum.FORCEUNIT                                      | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCPRESSUREMEASURE                            | Pressure                                | Pressure                            | Real      | Pascal                           | Pa                  | PA                  | (-1, 1, -2, 0, 0, 0, 0) | IFCUnitEnum.PRESSUREUNIT                                   | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 1    | \=N/m<sup>2</sup> = J/m<sup>3</sup>                                                                                             |
| IFCAREAMEASURE                                | Area                                    | Area                                | Real      | Square metre                     | m<sup>2</sup>       | M2                  | (2, 0, 0, 0, 0, 0, 0)   | IFCUnitEnum.AREAUNIT                                       | ✔️             | ❌                        | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCENERGYMEASURE                              | Energy                                  | Energy                              | Real      | Joule                            | J                   | J                   | (2, 1, -2, 0, 0, 0, 0)  | IFCUnitEnum.ENERGYUNIT                                     | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCPOWERMEASURE                               | Power                                   | Power                               | Real      | Watt                             | W                   | W                   | (2, 1, -3, 0, 0, 0, 0)  | IFCUnitEnum.POWERUNIT                                      | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCVOLUMEMEASURE                              | Volume                                  | Volume                              | Real      | Cubic metre                      | m<sup>3</sup>       | M3                  | (3, 0, 0, 0, 0, 0, 0)   | IFCUnitEnum.VOLUMEUNIT                                     | ✔️             | ❌                        | ✔️       | ✔️     | ✔️       | ✔️     | 1    |                                                                                                                                 |
| IFCPHMEASURE                                  | Acidity                                 | Acidity                             | Real      | pH                               | pH                  | PH                  |                         | IFCDerivedUnitEnum.PHUNIT                                  | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ✔️     | 2    | Changed name from PH to Acidity DECIDE                                                                                          |
| IFCLUMINOUSINTENSITYMEASURE                   | Luminous intensity                      | LuminousIntensity                   | Real      | Candela                          | cd                  | CD                  | (0, 0, 0, 0, 0, 0, 1)   | IFCUnitEnum.LUMINOUSINTENSITYUNIT                          | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 2    |                                                                                                                                 |
| IFCLUMINOUSFLUXMEASURE                        | Luminous flux                           | LuminousFlux                        | Real      | Lumen                            | lm                  | LM                  | (0, 0, 0, 0, 0, 0, 1)   | IFCUnitEnum.LUMINOUSFLUXUNIT                               | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 2    |                                                                                                                                 |
| IFCAMOUNTOFSUBSTANCEMEASURE                   | Amount of substance                     | AmountOfSubstance                   | Real      | Mole                             | mol                 | MOL                 | (0, 0, 0, 0, 0, 1, 0)   | IFCUnitEnum.AMOUNTOFSUBSTANCEUNIT                          | ✔️             | ✔️ (base)                | ✔️       | ✔️     | ✔️       | ✔️     | 2    |                                                                                                                                 |
| IFCILLUMINANCEMEASURE                         | Illuminance                             | Illuminance                         | Real      | Lux                              | lx                  | LUX                 | (-2, 0, 0, 0, 0, 0, 1)  | IFCUnitEnum.ILLUMINANCEUNIT                                | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 2    | \=lm/m<sup>2</sup>                                                                                                              |
| IFCELECTRICVOLTAGEMEASURE                     | Electric voltage                        | Voltage                             | Real      | Volt                             | V                   | V                   | (2, 1, -3, -1, 0, 0, 0) | IFCUnitEnum.ELECTRICVOLTAGEUNIT                            | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 2    | DECIDE QUDT has different name                                                                                                  |
| IFCELECTRICRESISTANCEMEASURE                  | Electric resistance                     | Resistance                          | Real      | Ohm                              | Ω                   | OHM                 | (2, 1, -3, -2, 0, 0, 0) | IFCUnitEnum.ELECTRICRESISTANCEUNIT                         | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 2    | DECIDE QUDT has different name. Other name: Impedance                                                                           |
| IFCSOLIDANGLEMEASURE                          | Solid angle                             | SolidAngle                          | Real      | Steradin                         | sr                  | SR                  |                         | IFCUnitEnum.SOLIDANGLEUNIT                                 | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    |                                                                                                                                 |
| IFCRADIOACTIVITYMEASURE                       | Radio activity                          | Radioactivity                       | Real      | Becquerel                        | Bq                  | BQ                  | (0, 0, -1, 0, 0, 0, 0)  | IFCUnitEnum.RADIOACTIVITYUNIT                              | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    |                                                                                                                                 |
| IFCELECTRICCHARGEMEASURE                      | Electric charge                         | ElectricCharge                      | Real      | Coulomb                          | C                   | C                   | (0, 0, 1, 1, 0, 0, 0)   | IFCUnitEnum.ELECTRICCHARGEUNIT                             | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    |                                                                                                                                 |
| IFCMAGNETICFLUXDENSITYMEASURE                 | Magnetic flux density                   | MagneticFluxDensity                 | Real      | Square metre kelvin per watt     | T                   | T                   | (0, 1, -2, -1, 0, 0, 0) | IFCUnitEnum.MAGNETICFLUXDENSITYUNIT                        | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    | \=Wb / m2                                                                                                                       |
| IFCABSORBEDDOSEMEASURE                        | Absorbed dose                           | AbsorbedDose                        | Real      | Gray                             | Gy                  | GY                  | (2, 0, -2, 0, 0, 0, 0)  | IFCUnitEnum.ABSORBEDDOSEUNIT                               | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    | \=J/kg =m<sup>2</sup>⋅s<sup>−2</sup>                                                                                            |
| IFCDOSEEQUIVALENTMEASURE                      | Dose equivalent                         | DoseEquivalent                      | Real      | Sievert                          | Sv                  | SV                  | (2, 0, -2, 0, 0, 0, 0)  | IFCUnitEnum.DOSEEQUIVALENTUNIT                             | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    | \=J/kg =m<sup>2</sup>⋅s<sup>−2</sup>                                                                                            |
| IFCMAGNETICFLUXMEASURE                        | Magnetic flux                           | MagneticFlux                        | Real      | Weber                            | Wb                  | WB                  | (2, 1, -2, -1, 0, 0, 0) | IFCDerivedUnitEnum.MAGNETICFLUXUNIT                        | ❌              | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    |                                                                                                                                 |
| IFCINDUCTANCEMEASURE                          | Inductance                              | Inductance                          | Real      | Henry                            | H                   | H                   | (2, 1, -2, -2, 0, 0, 0) | IFCUnitEnum.INDUCTANCEUNIT                                 | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    | \=Wb / A                                                                                                                        |
| IFCELECTRICCONDUCTANCEMEASURE                 | Electric conductance                    | ElectricConductance                 | Real      | Siemens                          | S                   | S                   | (-2, -1, 3, 2, 0, 0, 0) | IFCUnitEnum.ELECTRICCONDUCTANCEUNIT                        | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    | \=Ω<sup>\-1</sup>                                                                                                               |
| IFCELECTRICCAPACITANCEMEASURE                 | Electric capacitance                    | ElectricCapacitance                 | Real      | Farad                            | F                   | F                   | (-2, 1, 4, 1, 0, 0, 0)  | IFCUnitEnum.ELECTRICCAPACITANCEUNIT                        | ✔️             | ✔️ (derived)             | ✔️       | ✔️     | ✔️       | ✔️     | 3    |                                                                                                                                 |
| IFCMASSDENSITYMEASURE                         | Mass density                            | MassDensity                         | Real      | Kilogram per cubic metre         | Kg / m<sup>3</sup>  | KiloGM-PER-M3       | (-3, 1, 0, 0, 0, 0, 0)  | IFCDerivedUnitEnum.MASSDENSITYUNIT                         | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    | DECIDE rename to "Density"                                                                                                      |
| IFCACCELERATIONMEASURE                        | Acceleration                            | Acceleration                        | Real      | Metre per second squared         | m / s<sup>2</sup>   | M-PER-SEC2          | (1, 0, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.ACCELERATIONUNIT                        | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    |                                                                                                                                 |
| IFCTHERMALRESISTANCEMEASURE                   | Thermal resistance                      | ThermalResistance                   | Real      | Square metre kelvin per watt     | m<sup>2</sup> K / W | M2-K-PER-W          | (0, -1, 3, 0, 1, 0, 0)  | IFCDerivedUnitEnum.THERMALRESISTANCEUNIT                   | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    |                                                                                                                                 |
| IFCSECTIONMODULUSMEASURE                      | Section modulus                         | SectionModulus                      | Real      | Cubic metre                      | m<sup>3</sup>       | M3                  | (3, 0, 0, 0, 0, 0, 0)   | IFCDerivedUnitEnum.SECTIONMODULUSUNIT                      | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    |                                                                                                                                 |
| IFCMOMENTOFINERTIAMEASURE                     | Moment of inertia                       | SecondAxialMomentOfArea             | Real      | Quartic metre                    | m<sup>4</sup>       |                     | (4, 0, 0, 0, 0, 0, 0)   | IFCDerivedUnitEnum.MOMENTOFINERTIAUNIT                     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    | TODO this is wrong in IFC - Moment of inertia is in kg⋅m2 and not in m4. This is probably confused with SecondAxialMomentOfArea |
| IFCLINEARFORCEMEASURE                         | Linear force                            | ForcePerLength                      | Real      | Newton per metre                 | N / m               | N-PER-M             | (0, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.LINEARFORCEUNIT                         | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    | DECIDE QUDT has different name                                                                                                  |
| IFCLINEARMOMENTMEASURE                        | Linear moment                           | MomentPerLength                     | Real      | Newton metre per metre           | N m / m             | N-M-PER-M           | (1, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.LINEARMOMENTUNIT                        | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    | DECIDE QUDT has different name                                                                                                  |
| IFCTHERMALCONDUCTIVITYMEASURE                 | Thermal conductivity                    | ThermalConductivity                 | Real      | Watt per metre Kelvin            | W / m K             | W-PER-M-K           | (1, 1, -3, 0, -1, 0, 0) | IFCDerivedUnitEnum.THERMALCONDUCTANCEUNIT                  | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    |                                                                                                                                 |
| IFCTHERMALTRANSMITTANCEMEASURE                | Thermal transmittance                   | ThermalTransmittance                | Real      | Watt per square metre Kelvin     | W / m<sup>2</sup> K | W-PER-M2-K          | (0, 1, -3, 0, -1, 0, 0) | IFCDerivedUnitEnum.THERMALTRANSMITTANCEUNIT                | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 2    |                                                                                                                                 |
| IFCTHERMALEXPANSIONCOEFFICIENTMEASURE         | Thermal expansion coefficient           | ThermalExpansionCoefficient         | Real      | Reciprocal kelvin                | 1 / K               | PER-K               | (0, 0, 0, 0, -1, 0, 0)  | IFCDerivedUnitEnum.THERMALEXPANSIONCOEFFICIENTUNIT         | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCLUMINOUSINTENSITYDISTRIBUTIONMEASURE       | Luminous intensity distribution         | LuminousIntensityDistribution       | Real      | Candela per lumen                | cd / lm             | CD-PER-LM           |                         | IFCDerivedUnitEnum.LUMINOUSINTENSITYDISTRIBUTIONUNIT       | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCHEATINGVALUEMEASURE                        | Heating                                 | HeatCapacity                        | Real      | Joule per kelvin                 | J / K               | J-PER-K             | (2, 1, -2, 0, -1, 0, 0) | IFCDerivedUnitEnum.HEATINGVALUEUNIT                        | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE QUDT has different name                                                                                                  |
| IFCSPECIFICHEATCAPACITYMEASURE                | Specific heat capacity                  | SpecificHeatCapacity                | Real      | Joule per kilogram kelvin        | J / Kg K            | J-PER-KiloGM-K      | (2, 0, -2, 0, -1, 0, 0) | IFCDerivedUnitEnum.SPECIFICHEATCAPACITYUNIT                | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE remove word "specific"                                                                                                   |
| IFCTEMPERATUREGRADIENTMEASURE                 | Temperature gradient                    | TemperatureGradient                 | Real      | Kelvin per metre                 | K / m               | K-PER-M             | (-1, 0, 0, 0, 1, 0, 0)  | IFCDerivedUnitEnum.TEMPERATUREGRADIENTUNIT                 | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCTEMPERATURERATEOFCHANGEMEASURE             | Temperature rate of change              | TemperatureChangeRate               | Real      | Kelvin per second                | K / s               | K-PER-SEC           | (0, 0, -1, 0, 1, 0, 0)  | IFCDerivedUnitEnum.TEMPERATURERATEOFCHANGEUNIT             | ❌              | ❌                        | ❌        | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCMASSPERLENGTHMEASURE                       | Mass per length                         | LinearMassDensity                   | Real      | Kilogram per metre               | Kg / m              | KiloGM-PER-M        | (-1, 1, 0, 0, 0, 0, 0)  | IFCDerivedUnitEnum.MASSPERLENGTHUNIT                       | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCAREADENSITYMEASURE                         | Area density                            | AreaDensity                         | Real      | Kilogram per squere metre        | Kg / m<sup>2</sup>  | KiloGM-PER-M2       | (-2, 1, 0, 0, 0, 0, 0)  | IFCDerivedUnitEnum.AREADENSITYUNIT                         | ❌              | ❌                        | ❌        | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCMOLECULARWEIGHTMEASURE                     | Molecular weight                        | MolarMass                           | Real      | Kilogram per mole                | Kg / mol            | KiloGM-PER-MOL      | (0, 1, 0, 0, 0, -1, 0)  | IFCDerivedUnitEnum.MOLECULARWEIGHTUNIT                     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCMASSFLOWRATEMEASURE                        | Mass flow rate                          | MassFlowRate                        | Real      | Kilogram per second              | Kg / s              | KiloGM-PER-SEC      | (0, 1, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.MASSFLOWRATEUNIT                        | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCVAPORPERMEABILITYMEASURE                   | Vapor permeability                      | VaporPermeability                   | Real      | Kilogram per second metre Pascal | Kg / s m Pa         | KiloGM-PER-PA-SEC-M | (0, 0, 1, 0, 0, 0, 0)   | IFCDerivedUnitEnum.VAPORPERMEABILITYUNIT                   | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE rename to "Permeability" (remove Vapor)                                                                                  |
| IFCROTATIONALMASSMEASURE                      | Rotational mass                         | RotationalMass                      | Real      | Kilogram square metre            | Kg m<sup>2</sup>    | KiloGM-M2           | (2, 1, 0, 0, 0, 0, 0)   | IFCDerivedUnitEnum.ROTATIONALMASSUNIT                      | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCKINEMATICVISCOSITYMEASURE                  | Kinematic viscosity                     | KinematicViscosity                  | Real      | Square metre per second          | m<sup>2</sup> / s   | M2-PER-SEC          | (2, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.KINEMATICVISCOSITYUNIT                  | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | The SI unit (m2/s) doesn't match QUDT (stokes ST)                                                                               |
| IFCISOTHERMALMOISTURECAPACITYMEASURE          | Iso thermal moisture capacity           | IsoThermalMoistureCapacity          | Real      | Cubic metre per kilogram         | m<sup>3</sup> / Kg  | M3-PER-KiloGM       | (3, -1, 0, 0, 0, 0, 0)  | IFCDerivedUnitEnum.ISOTHERMALMOISTURECAPACITYUNIT          | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCMOISTUREDIFFUSIVITYMEASURE                 | Moisture diffusivity                    | MoistureDiffusivity                 | Real      | Cubic metre per second           | m<sup>3</sup> / s   | M3-PER-SEC          | (3, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.MOISTUREDIFFUSIVITYUNIT                 | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE Merge with volumetric flow?                                                                                              |
| IFCVOLUMETRICFLOWRATEMEASURE                  | Volumetric flow rate                    | VolumetricFlowRate                  | Real      | Cubic metre per second           | m<sup>3</sup> / s   | M3-PER-SEC          | (3, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.VOLUMETRICFLOWRATEUNIT                  | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCSECTIONALAREAINTEGRALMEASURE               | Sectional area integral                 | SectionalAreaIntegral               | Real      | Quintic metre                    | m<sup>5</sup>       | M5                  | (5, 0, 0, 0, 0, 0, 0)   | IFCDerivedUnitEnum.SECTIONALAREAINTEGRALUNIT               | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCWARPINGCONSTANTMEASURE                     | Warping constant                        | WarpingConstant                     | Real      | Sextic metre                     | m<sup>6</sup>       | M6                  | (6, 0, 0, 0, 0, 0, 0)   | IFCDerivedUnitEnum.WARPINGCONSTANTUNIT                     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCIONCONCENTRATIONMEASURE                    | Ion concentration measure               | IonConcentration                    | Real      | Mole per cubic metre             | mol / m<sup>3</sup> | MOL-PER-M3          | (-3, 1, 0, 0, 0, 0, 0)  | IFCDerivedUnitEnum.IONCONCENTRATIONUNIT                    | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCMODULUSOFELASTICITYMEASURE                 | Modulus of elasticity                   | ModulusOfElasticity                 | Real      | Pascal                           | Pa                  | PA                  | (-1, 1, -2, 0, 0, 0, 0) | IFCDerivedUnitEnum.MODULUSOFELASTICITYUNIT                 | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE Changed unit to Pascal. Consider also merging with Pressure (Pa)                                                         |
| IFCMODULUSOFLINEARSUBGRADEREACTIONMEASURE     | Modulus of linear subgrade reaction     | SubgradeModulus                     | Real      | Pascal                           | Pa                  | N-PER-M3            | (-1, 1, -2, 0, 0, 0, 0) | IFCDerivedUnitEnum.MODULUSOFLINEARSUBGRADEREACTIONUNIT     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE Changed unit to Pascal. Consider also merging with Pressure (Pa)                                                         |
| IFCSHEARMODULUSMEASURE                        | Shear modulus                           | ShearModulus                        | Real      | Pascal                           | Pa                  | PA                  | (-1, 1, -2, 0, 0, 0, 0) | IFCDerivedUnitEnum.SHEARMODULUSUNIT                        | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE Changed unit to Pascal. Consider also merging with Pressure (Pa)                                                         |
| IFCMODULUSOFSUBGRADEREACTIONMEASURE           | Modulus of subgrade reaction            | SubgradeModulus                     | Real      | Newton per cubic metre           | N / m<sup>3</sup>   | N-PER-M3            | (-2, 1, -2, 0, 0, 0, 0) | IFCDerivedUnitEnum.MODULUSOFSUBGRADEREACTIONUNIT           | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCTORQUEMEASURE                              | Torque                                  | Torque                              | Real      | Newton metre                     | N m                 | N-M                 | (2, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.TORQUEUNIT                              | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCMODULUSOFROTATIONALSUBGRADEREACTIONMEASURE | Modulus of rotational subgrade reaction | ModulusOfRotationalSubgradeReaction | Real      | Newton metre per metre radian    | N m / m rad         | N-M-PER-M-RAD       | (1, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.MODULUSOFROTATIONALSUBGRADEREACTIONUNIT | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE same as with angle - degree or radians                                                                                   |
| IFCROTATIONALSTIFFNESSMEASURE                 | Rotational stiffness                    | RotationalStiffness                 | Real      | Newton metre per radian          | N m / rad           | N-M-PER-RAD         | (2, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.ROTATIONALSTIFFNESSUNIT                 | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE same as with angle - degree or radians                                                                                   |
| IFCWARPINGMOMENTMEASURE                       | Warping moment                          | WarpingMoment                       | Real      | Newton square metre              | N m<sup>2</sup>     | N-M2                | (3, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.WARPINGMOMENTUNIT                       | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCDYNAMICVISCOSITYMEASURE                    | Dynamic viscosity                       | DynamicViscosity                    | Real      | Pascal second                    | Pa s                | PA-SEC              | (-1, 1, -1, 0, 0, 0, 0) | IFCDerivedUnitEnum.DYNAMICVISCOSITYUNIT                    | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCCURVATUREMEASURE                           | Curvature                               | Curvature                           | Real      | Radian per metre                 | rad / m             | RAD-PER-M           | (-1, 0, 0, 0, 0, 0, 0)  | IFCDerivedUnitEnum.CURVATUREUNIT                           | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE same as with angle - degree or radians                                                                                   |
| IFCANGULARVELOCITYMEASURE                     | Angular velocity                        | AngularVelocity                     | Real      | Radian per second                | rad / s             | RAD-PER-SEC         | (0, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.ANGULARVELOCITYUNIT                     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE same as with angle - degree or radians                                                                                   |
| IFCHEATFLUXDENSITYMEASURE                     | Heat flux density                       | HeatFluxDensity                     | Real      | Watt per square metre            | W / m<sup>2</sup>   | W-PER-M2            | (0, 1, -3, 0, 0, 0, 0)  | IFCDerivedUnitEnum.HEATFLUXDENSITYUNIT                     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    |                                                                                                                                 |
| IFCTHERMALADMITTANCEMEASURE                   | Thermal admittance                      | ThermalAdmittance                   | Real      | Watt per square metre Kelvin     | W / m<sup>2</sup> K | W-PER-M2-K          | (0, 1, -3, 0, -1, 0, 0) | IFCDerivedUnitEnum.THERMALADMITTANCEUNIT                   | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3    | DECIDE Consider merging with Thermal Transmittance                                                                              |
| IFCCONTEXTDEPENDENTMEASURE                    | Context dependent                       |                                     | String    |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure.                                                                                                  |
| IFCCOUNTMEASURE                               | Count                                   |                                     | Integer   |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple integer property.                                                                 |
| IFCDESCRIPTIVEMEASURE                         | Descriptive                             |                                     | String    |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple textual property.                                                                 |
| IFCMONETARYMEASURE                            | Monetary                                |                                     | Real      |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple numeric property.                                                                 |
| IFCNORMALISEDRATIOMEASURE                     | Normalised ratio                        |                                     | Real      |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple numeric property.                                                                 |
| IFCNUMERICMEASURE                             | Numeric                                 |                                     | Real      |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple numeric property.                                                                 |
| IFCPOSITIVERATIOMEASURE                       | Positive ratio                          |                                     | Real      |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | Restriction does not make it a separate measure.                                                                                |
| IFCRATIOMEASURE                               | Ratio                                   |                                     | Real      |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple numeric property.                                                                 |
| IFCINTEGERCOUNTRATEMEASURE                    | Integer count rate                      |                                     | Integer   |                                  |                     |                     |                         |                                                            | ❌              | ❌                        | ❔        | ❔      | ✔️       | ❌      | ⛔️   | No need for dedicated measure. It is a simple integer property.                                                                 |
| IFCSOUNDPOWERMEASURE                          | Sound power                             | SoundPower                          | Real      | Watt                             | W                   | W                   |                         | IFCDerivedUnitEnum.SOUNDPOWERUNIT                          | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3   | DECIDE - One at the source (power), one at a distance from it (exposure)                                                |
| IFCSOUNDPOWERLEVELMEASURE                     | Sound power level                       | SoundPowerLevel                     | Real      | Decibel                          | db                  | DB                  |                         | IFCDerivedUnitEnum.SOUNDPOWERLEVELUNIT                     | ❌              | ❌                        | ❌        | ✔️     | ✔️       | ❔     | 3    | DECIDE - One at the source (power), one at a distance from it (exposure)                                               |
| IFCSOUNDPRESSURELEVELMEASURE                  | Sound pressure level                    | SoundPressureLevel                  | Real      | Decibel                          | db                  | DB                  |                         | IFCDerivedUnitEnum.SOUNDPRESSURELEVELUNIT                  | ❌              | ❌                        | ❌        | ✔️     | ✔️       | ❔      | 3   | DECIDE - One at the source (power), one at a distance from it (exposure)                                               |
| IFCSOUNDPRESSUREMEASURE                       | Sound pressure                          | SoundPressure                       | Real      | Pascal                           | Pa                  | PA                  |                         | IFCDerivedUnitEnum.SOUNDPRESSUREUNIT                       | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❔      | 3   | DECIDE - One at the source (power), one at a distance from it (exposure)                                                |
| IFCPOSITIVEPLANEANGLEMEASURE                  | Positive plane angle                    |                                     | Real      | Radian                           | rad                 |                     |                         | IFCUnitEnum.PLANEANGLEUNIT                                 | ✔️             | ❌                        | ✔️       | ✔️     | ✔️       | ❌      | ⛔️   | Restriction does not make it a separate measure.                                                                                |
| IFCROTATIONALFREQUENCYMEASURE                 | Rotational frequency                    |                                     | Real      | Reciprocal kelvin                | Hz                  |                     | (0, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.ROTATIONALFREQUENCYUNIT                 | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❌      | ⛔️   | Still a frequency.                                                                                                              |
| IFCINTEGERCOUNTRATEMEASURE                    | Integer count rate                      |                                     | Integer   | Reciprocal second                | 1 / s               |                     | (0, 0, -1, 0, 0, 0, 0)  | IFCDerivedUnitEnum.INTEGERCOUNTRATEUNIT                    | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❌      | ⛔️   | Merge with Frequency (Hz)                                                                                                       |
| IFCNONNEGATIVELENGTHMEASURE                   | Non-negative length                     |                                     | Real      | Metre                            | m                   |                     | (1, 0, 0, 0, 0, 0, 0)   | IFCUnitEnum.LENGTHUNIT                                     | ✔️             | ❌                        | ❌        | ✔️     | ✔️       | ❌      | ⛔️   | Restriction does not make it a separate measure.                                                                                |
| IFCPOSITIVELENGTHMEASURE                      | Positive length                         |                                     | Real      | Metre                            | m                   |                     | (1, 0, 0, 0, 0, 0, 0)   | IFCUnitEnum.LENGTHUNIT                                     | ✔️             | ❌                        | ✔️       | ✔️     | ✔️       | ❌      | ⛔️   | Restriction does not make it a separate measure.                                                                                |
| IFCPLANARFORCEMEASURE                         | Planar force                            |                                     | Real      | Pascal                           | Pa                  |                     | (-1, 1, -2, 0, 0, 0, 0) | IFCDerivedUnitEnum.PLANARFORCEUNIT                         | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❌      | ⛔️   | Instead, use Pressure (Pa) or Force (N)                                                                                         |
| IFCLINEARSTIFFNESSMEASURE                     | Linear stiffness                        |                                     | Real      | Newton per metre                 | N / m               |                     | (0, 1, -2, 0, 0, 0, 0)  | IFCDerivedUnitEnum.LINEARSTIFFNESSUNIT                     | ❌              | ❌                        | ✔️       | ✔️     | ✔️       | ❌      | ⛔️   | Merge with linear force                                                                                                         |
