Index Page
EXPRESS Definition |
EXPRESS-G Diagram |
IDL Definition |
The IfcMeasureResource schema is adapted from the ISO 10303 part 41 Measure schema and specifies units and measures that may be assigned to quantities.
The fundamental unit type used in this schema is based on the SI system defined in ISO 1000. Units in measurement systems other than SI may be derived using this schema.
EXPRESS Definition
A simple Boolean as data type within Property Sets.
Type = BOOLEAN
EXPRESS Definition
A simple Integer as data type within Property Sets. IfcInteger contains a signed integer number value.
Type = INTEGER
EXPRESS Definition
A simple Real as data type within Property Sets. IfcReal has a signed real number value.
Type = REAL
EXPRESS Definition
A simple String as data type within Property Sets.
Type = STRING
Type IfcAmountOfSubstanceMeasure
EXPRESS Definition
An amount of substance measure is the value for the quantity of a substance when compared with the number of atoms in 0.012 kilogram of carbon 12.
Type = REAL
EXPRESS Definition
An area measure is the value of the extent of a surface.
Type = REAL
Type IfcCompoundPlaneAngleMeasure
EXPRESS Definition
A compound measure of plane angle in degrees minutes and seconds of arc.
IfcCompoundPlaneAngleMeasure is used where angles need to be described to an accuracy of less than one degree and expressed as parts of an arc. It may be used for angular measurement by surveyors or for other angular measurements where precision is required. It should not be used for angular measurements which may be expressed in decimal fractions of a degree; for which purpose the IfcPlaneAngleMeasure is provided.
Type = LIST [3:3] INTEGER
Formal Propositions:
WR1 |
{ 0 <= SELF[1] < 360 } |
WR2 |
{ 0 <= SELF[2] < 60 } |
WR3 |
{ 0 <= SELF[3] < 60 } |
Type IfcContextDependentMeasure
EXPRESS Definition
A context dependent measure is a general purpose real number measure type.
Type = REAL
EXPRESS Definition
A count measure is the value of a count.
Type = NUMBER
EXPRESS Definition
A descriptive measure is a human interpretable definition of a quantifiable value.
Type = STRING
Type IfcElectricCurrentMeasure
EXPRESS Definition
An electric current measure is the value for the movement of electrically charged particles.
Type = REAL
EXPRESS Definition
A length measure is the value of a distance.
Type = REAL
Type IfcLuminousIntensityMeasure
EXPRESS Definition
A luminous intensity measure is the value for the brightness of a body.
Type = REAL
EXPRESS Definition
A mass measure is the value of the amount of matter that a body contains.
Type = REAL
EXPRESS Definition
A measure value is a value as defined in ISO 31-0 (clause 2).
Type = SELECT
Selections are:-
IfcLengthMeasure |
|
IfcMassMeasure |
|
IfcTimeMeasure |
|
IfcElectricCurrentMeasure |
|
IfcThermodynamicTemperatureMeasure |
|
IfcAmountOfSubstanceMeasure |
|
IfcLuminousIntensityMeasure |
|
IfcPlaneAngleMeasure |
|
IfcSolidAngleMeasure |
|
IfcAreaMeasure |
|
IfcVolumeMeasure |
|
IfcRatioMeasure |
|
IfcParameterValue |
|
IfcNumericMeasure |
|
IfcContextDependentMeasure |
|
IfcDescriptiveMeasure |
|
IfcPositiveLengthMeasure |
|
IfcPositivePlaneAngleMeasure |
|
IfcPositiveRatioMeasure |
|
IfcCountMeasure |
|
IfcCompoundPlaneAngleMeasure |
|
IfcTimeDurationMeasure |
|
IfcTimeStamp |
|
IfcBoolean |
|
IfcInteger |
|
IfcReal |
|
IfcString |
|
EXPRESS Definition
A numeric measure is the numeric value of a physical quantity.
Type = NUMBER
EXPRESS Definition
A parameter value is the value which specifies the amount of a parameter in some parameter space.
Type = REAL
EXPRESS Definition
A plane angle measure is the value of an angle in a plane.
IfcPlaneAngleMeasure is used where angles need to be described to an accuracy of less than one degree and expressed as decimal parts of an angle. It is widely used for angular measurement except for situations where accuracy needs to be defined using arc measurement; for which purpose the IfcCompoundPlaneAngleMeasure is provided.
Type = REAL
EXPRESS Definition
A positive length measure is a length measure that is greater than zero.
Type = IfcLengthMeasure
WR1 |
SELF > 0 |
Type IfcPositivePlaneAngleMeasure
EXPRESS Definition
A positive plane angle measure is a plane angle measure that is greater than zero.
Type = IfcPlaneAngleMeasure
WR1 |
SELF > 0 |
EXPRESS Definition
A positive ratio measure is a ratio measure that is greater than zero.
Type = IfcRatioMeasure
WR1 |
SELF > 0 |
EXPRESS Definition
A ratio measure is the value of the relation between two physical quantities that are of the same kind.
Type = REAL
EXPRESS Definition
A solid angle measure is the value of an angle in a solid.
Type = REAL
Type IfcThermodynamicTemperatureMeasure
EXPRESS Definition
A thermodynamic temperature measure is the value for the degree of heat of a body.
Type = REAL
EXPRESS Definition
A time measure is the value of the duration of periods.
Type = REAL
EXPRESS Definition
A period of time measured without reference to date.
Type = REAL
EXPRESS Definition
An indication of date and time by measuring the number of seconds which have elapsed since the beginning of the year 1970.
Type = INTEGER
EXPRESS Definition
A volume measure is the value of the solid content of a body.
Type = REAL
EXPRESS Definition
Predefined derived units, as used within the semantic model and Property Sets of this IFC Release.
Type = ENUMERATION
Allowed values are:-
VolumetricFlowrateUnit |
|
MassFlowrateUnit |
|
PressureUnit |
|
EnergyUnit |
|
PowerUnit |
|
AngularVelocityUnit |
|
LinearVelocityUnit |
|
RotationalFrequencyUnit |
|
HeatfluxDensityUnit |
|
MassDensityUnit |
|
ThermalResistanceUnit |
|
ThermalTransmittanceUnit |
|
VoltageUnit |
|
DynamicViscosityUnit |
|
KinematicViscosityUnit |
|
Unspecified |
|
EXPRESS Definition
An SI prefix is the name of a prefix that may be associated with an SI unit. The definitions of SI prefixes are specified in ISO 1000 (clause 3).
Type = ENUMERATION
Allowed values are:-
EXA |
: see ISO 1000 (clause 3). |
PETA |
: see ISO 1000 (clause 3). |
TERA |
: see ISO 1000 (clause 3). |
GIGA |
: see ISO 1000 (clause 3). |
MEGA |
: see ISO 1000 (clause 3). |
KILO |
: see ISO 1000 (clause 3). |
HECTO |
: see ISO 1000 (clause 3). |
DECA |
: see ISO 1000 (clause 3). |
DECI |
: see ISO 1000 (clause 3). |
CENTI |
: see ISO 1000 (clause 3). |
MILLI |
: see ISO 1000 (clause 3). |
MICRO |
: see ISO 1000 (clause 3). |
NANO |
: see ISO 1000 (clause 3). |
PICO |
: see ISO 1000 (clause 3). |
FEMTO |
: see ISO 1000 (clause 3). |
ATTO |
: see ISO 1000 (clause 3). |
EXPRESS Definition
An SI unit name is the name of an SI unit. The definitions of the names of SI units are specified in ISO 1000 (clause 2).
Type = ENUMERATION
Allowed values are:-
METRE |
: see ISO 1000 (clause 2.1). |
SQUARE_METRE |
|
CUBIC_METRE |
|
GRAM |
: see ISO 1000 (clause 2.1). |
SECOND |
: see ISO 1000 (clause 2.1). |
AMPERE |
: see ISO 1000 (clause 2.1). |
KELVIN |
: see ISO 1000 (clause 2.1). |
MOLE |
: see ISO 1000 (clause 2.1). |
CANDELA |
: see ISO 1000 (clause 2.1). |
RADIAN |
: see ISO 1000 (clause 2.2). |
STERADIAN |
: see ISO 1000 (clause 2.2). |
HERTZ |
: see ISO 1000 (clause 2.3). |
NEWTON |
: see ISO 1000 (clause 2.3). |
PASCAL |
: see ISO 1000 (clause 2.3). |
JOULE |
: see ISO 1000 (clause 2.3). |
WATT |
: see ISO 1000 (clause 2.3). |
COULOMB |
: see ISO 1000 (clause 2.3). |
VOLT |
: see ISO 1000 (clause 2.3). |
FARAD |
: see ISO 1000 (clause 2.3). |
OHM |
: see ISO 1000 (clause 2.3). |
SIEMENS |
: see ISO 1000 (clause 2.3). |
WEBER |
: see ISO 1000 (clause 2.3). |
TESLA |
: see ISO 1000 (clause 2.3). |
HENRY |
: see ISO 1000 (clause 2.3). |
DEGREE_CELSIUS |
: see ISO 1000 (clause 2.3). |
LUMEN |
: see ISO 1000 (clause 2.3). |
LUX |
: see ISO 1000 (clause 2.3). |
BECQUEREL |
: see ISO 1000 (clause 2.3). |
GRAY |
: see ISO 1000 (clause 2.3). |
SIEVERT |
: see ISO 1000 (clause 2.3). |
EXPRESS Definition
Allowed units types for the standard measure types. There is a named data type applied for each unit type, the assignment of the actual units to that named data types is handled by the IfcUnitAssignment.
Type = ENUMERATION
Allowed values are:-
LengthUnit |
|
MassUnit |
|
TimeUnit |
|
DurationUnit |
|
ElectricCurrentUnit |
|
ThermodynamicTemperatureUnit |
|
AmountOfSubstanceUnit |
|
LuminousIntensityUnit |
|
PlaneAngleUnit |
|
SolidAngleUnit |
|
AreaUnit |
|
VolumeUnit |
|
RatioUnit |
|
Unspecified |
|
EXPRESS Definition
A unit is a physical quantity, with a value of one, which is used as a standard in terms of which other quantities are expressed.
Type = SELECT
Selections are:-
IfcDerivedUnit |
IfcNamedUnit |
EXPRESS Definition
An context dependent unit is a unit which is not related to the SI system.
The number of parts in an assembly is a physical quantity measured in units that may be called "parts" but which cannot be related to an SI unit.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Name |
The word, or group of words, by which the context dependent unit is referred to. |
STRING |
see type |
see type |
empty string |
No Formal Propositions defined at this level.
EXPRESS Definition
A conversion based unit is a unit that is defined based on a measure with unit.
An inch is a converted unit. It is from the Imperial system, its name is "inch" and it can be related to the SI unit, millimetre, through a measure with unit whose value is 25.4 millimetre. A foot is also a converted unit. It is from the Imperial system, its name is \foot" and it can be related to an SI unit, millimetre, either directly or through the unit called "inch".
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Name |
The word, or group of words, by which the conversion based unit is referred to. |
STRING |
see type |
see type |
empty string |
|
ConversionFactor |
The physical quantity from which the converted unit is derived. |
see type |
see type |
see type |
No Formal Propositions defined at this level.
EXPRESS Definition
A derived unit is an expression of units.
Example: "Newton per square millimetre" is a derived unit.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Elements |
The group of units and their exponents that define the derived unit. |
SET [1:?] OF IfcDerivedUnitElement |
1 |
N |
see WR1 |
|
UnitType |
Name of the derived unit – selected from a predefined enumeration for use in IFC models. |
VolumetricFlowrateUnit |
Unspecified |
Unspecified |
|
DER |
Dimensions |
Dimensional exponents are derived using the function IfcDerivedDimensionalExponents using (SELF) as the input value. |
see type |
see type |
n/a |
Formal Propositions:
WR1 |
There shall be either more than one member in the elements set or the value of the exponent of the single element of the elements set shall not be equal to one. |
EXPRESS Definition
A derived unit element is one of the unit quantities which makes up a derived unit.
EXAMPLE: Newtons per square millimetre is a derived unit. It has two elements, Newton whose exponent has a value of 1 and millimetre whose exponent is -2.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Unit |
The fixed quantity which is used as the mathematical factor. |
see type |
see type |
see type |
|
|
Exponent |
The power that is applied to the unit attribute. |
INTEGER |
see type |
see type |
1 |
No Formal Propositions defined at this level.
EXPRESS Definition
The dimensionality of any quantity can be expressed as a product of powers of the dimensions of base quantities. The dimensional exponents entity defines the powers of the dimensions of the base quantities. All the physical quantities are founded on seven base quantities (ISO 31 (clause 2)).
Length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity are the seven base quantities.
EXAMPLE: A length of 2 millimetres has a length exponent of 1. The remaining exponents are equal to 0.
EXAMPLE: A velocity of 2 millimetres per second has a length exponent of 1 and a time exponent of -1. The remaining exponents are equal to 0.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
LengthExponent |
The power of the length base quantity. |
INTEGER |
see type |
see type |
1 |
|
MassExponent |
The power of the mass base quantity. |
INTEGER |
see type |
see type |
0 |
|
TimeExponent |
The power of the time base quantity. |
INTEGER |
see type |
see type |
0 |
|
ElectricCurrentExponent |
The power of the electric current base quantity. |
INTEGER |
see type |
see type |
0 |
|
ThermodynamicTemperatureExponent |
The power of the thermodynamic temperature base quantity. |
INTEGER |
see type |
see type |
0 |
|
AmountOfSubstanceExponent |
The power of the amount of substance base quantity. |
INTEGER |
see type |
see type |
0 |
|
LuminousIntensityExponent |
The power of the luminous intensity base quantity. |
INTEGER |
see type |
see type |
0 |
No Formal Propositions defined at this level.
EXPRESS Definition
A measure with unit is the specification of a physical quantity as defined in ISO 31 (clause 2).
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
ValueComponent |
the value of the physical quantity when expressed in the specified units. |
see type |
see type |
IfcLengthMeasure |
|
|
UnitComponent |
the unit in which the physical quantity is expressed. |
see type |
see type |
IfcNamedUnit |
Informal Propositions:
IR1 |
The unit shall be a valid unit for the kind of measure. |
EXPRESS Definition
A named unit is a unit quantity associated with the word, or group of words, by which the unit is identified.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Dimensions |
The exponents of the base properties by which the named unit is defined. |
see type |
see type |
1,0,0,0,0,0,0 |
|
|
UnitType |
Type of unit used. |
see type |
see type |
LengthUnit |
Formal Propositions:
WR1 |
Correct dimensions are established through the function IfcCorrectDimensions. IfcCorrectDimensions (SELF.UnitType, Self.Dimensions) |
EXPRESS Definition
An SI unit is the fixed quantity used as a standard in terms of which items are measured as defined by ISO 1000 (clause 2).
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Prefix |
The SI Prefix |
EXA |
ATTO |
MILLI |
|
|
Name |
The word, or group of words, by which the SI unit is referred to. |
METRE |
SIEVERT |
METRE |
|
DER |
Dimensions |
Dimensions are derived from the function IfcDimensions forSiUnit |
see type |
see type |
1,0,0,0,0,0,0 |
No Formal Propositions defined at this level.
EXPRESS Definition
A set of units which may be assigned.
A project has a unit assignment which establishes the set of units which will be used. Other objects may have local unit assignments if there is a requirement for them to make use of units which do not fall within the project unit assignment.
|
Attribute / Relation |
Definition |
Data or Relation Type |
Min |
Max |
Default |
|
Units |
Units to be included within a unit assignment. |
Set [1:?] IfcUnit |
1 |
N |
1 |
No Formal Propositions defined at this level.
EXPRESS Definition
The correct dimensions function returns the dimensional exponents of the given unit type.
Argument definitions: M: (input) the unit type for which the dimensional exponents are tested – from the enumeration IfcUnitTypeEnum. Dim (input) dimensional exponents for this unit type
Function IfcDeriveDimensionalExponents
EXPRESS Definition
This function determines the dimensional exponents of a unit. For named units the dimensions attribute is returned and for derived units the dimensional exponents are calculated from its elements.
Argument definitions:
X: (input) the unit that the dimensional exponents are being derived from.
Function IfcDimensionsForSiUnit
EXPRESS Definition
The dimensions for SI unit function returns the dimensional exponents of the given SI - unit.
Argument definitions:
N : (input) the name of the unit for which the dimensional exponents will be returned.