IfcElementQuantity

Semantic definitions at the entity

Entity definition

An IfcElementQuantity defines a set of derived measures of an element's physical property. Elements could be spatial structure elements (like buildings, storeys, or spaces) or building elements (like walls, slabs, finishes). The IfcElementQuantity gets assigned to the element by using the IfcRelDefinesByProperties relationship.

The optional MethodOfMeasurement attribute defines the code, e.g. from a standard method of measurement, which had been used to calculate the element quantity.

NOTE The recognizable values for the name and the method of measurement attributes have to be agreed upon in further agreement documents, such as implementers agreements. Some of these agreements might be limited to a certain region, to which the method of measurement applies.

The name attribute, given at the individual Quantities provides a recognizable semantic meaning of the element quantity. Both information is needed to establish a precise meaning for the measure value. An optional description may be assigned to each of the Quantities. All quantities assigned by a single instance of IfcElementQuantity are deemed to have been generated according to the same method of measurement. However several instances of IfcElementQuantity are assignable to an element, thus allowing for an element having quantities generated according to several methods of measurement.

EXAMPLE To exchange the net floor area of spaces in the German region (as IfcSpace), the name might be 'Netto-Grundfläche' (net floor area), and the method of measurement might be accordingly 'DIN277-2' (German industry norm no. 277 edition 2).

EXAMPLE The same instance of IfcSpace may have a different area measure assigned in the German region according to a housing regulation, the name would be 'Wohnfläche' and the method of measurement would be '2.BV'. It would be attached to the IfcSpace by a separate IfcRelDefinesByProperties relationship.

The IfcElementQuantity can have the following subtypes of IfcPhysicalQuantity within its SET of Quantities, which count for the basis measure types used:

count measure
weight measure
length measure
area measure
volume measure
time measure

Base quantities are quantity definitions that are independent of a particular method of measurement and therefore internationally applicable. Base quantities are defined as gross and net values and provided by measurement of the correct geometric shape representation of the element. This specification includes a set of base quantity definition. See each subtype of IfcElement for applicable base quantities.

The following general agreements apply for each base quantity set

IfcElementQuantity.Name = <name of the qto definition template>
IfcElementQuantity.MethodOfMeasurement = 'BaseQuantities'
IfcElementQuantity.Quantities = SET of subtypes of IfcPhysicalSimpleQuantity with values for the Name attribute as published as part of this specifciation.

HISTORY New entity in IFC2x.

IFC4 CHANGE Subtyped from new intermediate IfcQuantitySet supertype.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
5	MethodOfMeasurement	IfcLabel	[0:1]	Name of the method of measurement used to calculate the element quantity. The method of measurement attribute has to be made recognizable by further agreements.	X
6	Quantities	IfcPhysicalQuantity	S[1:?]	The individual quantities for the element, can be a set of length, area, volume, weight or count based quantities.	X

Formal Propositions

Rule	Description
UniqueQuantityNames	Every individual IfcPhysicalQuantity within the set Quantities shall have a unique Name attribute value. HISTORY New rule in IFC4

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE only the last modification in stored - either as addition, deletion or modification.	X
3	Name	IfcLabel	[0:1]	Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.	X
4	Description	IfcText	[0:1]	Optional description, provided for exchanging informative comments.	X
IfcPropertyDefinition
	HasContext	IfcRelDeclares @RelatedDefinitions	S[0:1]		X
	HasAssociations	IfcRelAssociates @RelatedObjects	S[0:?]	Reference to the relationship IfcRelAssociates and thus to those externally defined concepts, like classifications, documents, or library information, which are associated to the property definition.	X
IfcPropertySetDefinition
	DefinesType	IfcTypeObject @HasPropertySets	S[0:?]	The type object to which the property set is assigned. The property set acts as a shared property set to all occurrences of the type object. NOTE The relationship between the IfcPropertySetDefinition and the IfcTypeObject is a direct relationship, not utilizing IfcRelDefinesByProperties, for maintaining compatibility with earlier releases of this standard.	X
	IsDefinedBy	IfcRelDefinesByTemplate @RelatedPropertySets	S[0:?]	Relation to the property set template, via the objectified relationship IfcRelDefinesByTemplate, that, if given, provides the definition template for the property set or quantity set and its properties.	X
	DefinesOccurrence	IfcRelDefinesByProperties @RelatingPropertyDefinition	S[0:?]	Reference to the relation to one or many object occurrences that are characterized by the property set definition. A single property set can be assigned to multiple object occurrences using the objectified relationship IfcRefDefinesByProperties.	X
IfcQuantitySet
IfcElementQuantity
5	MethodOfMeasurement	IfcLabel	[0:1]	Name of the method of measurement used to calculate the element quantity. The method of measurement attribute has to be made recognizable by further agreements.	X
6	Quantities	IfcPhysicalQuantity	S[1:?]	The individual quantities for the element, can be a set of length, area, volume, weight or count based quantities.	X

Definitions applying to Common Use Definitions

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Common Use Definitions
	Revision Control	Common Use Definitions

Formal representations

XSD Specification

 <xs:element name="IfcElementQuantity" type="ifc:IfcElementQuantity" substitutionGroup="ifc:IfcQuantitySet" nillable="true"/>

 <xs:complexType name="IfcElementQuantity">

  <xs:complexContent>

   <xs:extension base="ifc:IfcQuantitySet">

    <xs:sequence>

     <xs:element name="Quantities">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcPhysicalQuantity" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcPhysicalQuantity"/>

       <xs:attribute ref="ifc:cType" fixed="set"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

    </xs:sequence>

    <xs:attribute name="MethodOfMeasurement" type="ifc:IfcLabel" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcElementQuantity

 SUBTYPE OF (IfcQuantitySet);

  MethodOfMeasurement : OPTIONAL IfcLabel;

  Quantities : SET [1:?] OF IfcPhysicalQuantity;

 WHERE

  UniqueQuantityNames : IfcUniqueQuantityNames(Quantities);
END_ENTITY;

 EXPRESS-G diagram

Link to this page

Item	Change	Description
IFC2x3 to IFC4
IfcElementQuantity
OwnerHistory	MODIFIED	Instantiation changed to OPTIONAL.

	frei definierbare Elementmengenliste
	Element Quantity
	Quantité d'élément