IFC (IFC4X3_ADD2) under development IfcElementQuantity

RV ⓘ
AbV ⓘ Semantic 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.

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.

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 Entity inheritance Attributes

# Attribute Type Description
IfcRoot (4)
1 GlobalId IfcGloballyUniqueId

Assignment of a globally unique identifier within the entire software world.

2 OwnerHistory OPTIONAL IfcOwnerHistory

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,

3 Name OPTIONAL IfcLabel

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.

4 Description OPTIONAL IfcText

Optional description, provided for exchanging informative comments.

IfcPropertyDefinition (2)
HasContext SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions

Reference to the relationship IfcRelDeclares and thus to the IfcProject or IfcProjectLibrary.

HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects

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.

IfcPropertySetDefinition (3)
DefinesType SET [0:?] OF IfcTypeObject FOR HasPropertySets

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.

IsDefinedBy SET [0:?] OF IfcRelDefinesByTemplate FOR RelatedPropertySets

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.

DefinesOccurrence SET [0:?] OF IfcRelDefinesByProperties FOR RelatingPropertyDefinition

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.

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IfcElementQuantity (2)
5 MethodOfMeasurement OPTIONAL IfcLabel

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.

6 Quantities SET [1:?] OF IfcPhysicalQuantity

The individual quantities for the element, can be a set of length, area, volume, weight or count based quantities.

Table Formal propositions

Name Description

Every individual IfcPhysicalQuantity within the set Quantities shall have a unique Name attribute value.

Table Concept usage

Concept Usage Description
IfcRoot (2)
Revision Control General

Ownership, history, and merge state is captured using IfcOwnerHistory.

Software Identity General

IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.

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Table Formal representation

ENTITY IfcElementQuantity
 SUBTYPE OF (IfcQuantitySet);
	MethodOfMeasurement : OPTIONAL IfcLabel;
	Quantities : SET [1:?] OF IfcPhysicalQuantity;
	UniqueQuantityNames : IfcUniqueQuantityNames(Quantities);
END_ENTITY; References

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