Ensemble de propriétés
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IfcPropertySet defines all dynamically extensible properties. The property set is a container class that holds properties within a property tree. These properties are interpreted according to their name attribute.

The same IfcPropertySet can be assigned to multiple object occurrences; it should then be assigned by a single instance of IfcRelDefinedByProperties to a set of related objects. Those property sets are referred to as shared property sets. It can also be assigned to an object type.

An IfcPropertySetTemplate may define the underlying structure, i.e. the required name, the applicable object or object types to which the property set can be attached, and the individual properties that maybe included.

NOTE  See IfcRelDefinesByType for how to override property sets assigned to an object type within the object occurrence.
HISTORY  New entity in IFC1.0
IFC4 CHANGE  All statically defined property set entities are no longer subtypes of IfcPropertySet.

Relationship use definition

Property sets are related to other objects by using the relationship object that refers to the corresponding object:

Attribute use definition

Instances of IfcPropertySet are used to assign named sets of individual properties (complex or single properties). Each individual property has a significant name string. Some property sets are included in the IFC specification and have a predefined set of properties indicated by assigning a significant name. These property sets are listed under "property sets" main menu item within this specification and from the object documentation sheet for those object to which they are applicable. The naming convention "Pset_Xxx" applies to all those property sets that are defined as part of the IFC specification and it shall be used as the value of the Name attribute.

In addition any user defined property set can be captured. Property sets that are not declared as part of the IFC specification shall have a Name value not including the "Pset_" prefix.

XSD Specification:

 <xs:element name="IfcPropertySet" type="ifc:IfcPropertySet" substitutionGroup="ifc:IfcPropertySetDefinition" nillable="true"/>
 <xs:complexType name="IfcPropertySet">
   <xs:extension base="ifc:IfcPropertySetDefinition">
     <xs:element name="HasProperties">
        <xs:element ref="ifc:IfcProperty" maxOccurs="unbounded"/>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcProperty"/>
       <xs:attribute ref="ifc:cType" fixed="set"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>

EXPRESS Specification:

ENTITY IfcPropertySet
SUBTYPE OF IfcPropertySetDefinition;
HasProperties : SET [1:?] OF IfcProperty;
ExistsName : EXISTS(SELF\IfcRoot.Name);
UniquePropertyNames : IfcUniquePropertyName(HasProperties);

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

HasProperties : Contained set of properties. For property sets defined as part of the IFC Object model, the property objects within a property set are defined as part of the standard. If a property is not contained within the set of predefined properties, its value has not been set at this time.

Formal Propositions:

ExistsName : The Name attribute has to be provided. The attribute is used to specify the signifier of the property set. The properties that are allowed to be attached to a particular property set may be given within the property set definition part of the IFC specification. Those property set definitions are references in the semantic definition section of the individal subtypes of IfcObjectDefinition.
UniquePropertyNames : Every individual subtype of IfcProperty within the property set shall have a unique Name attribute value.

Inheritance Graph:

ENTITY IfcPropertySet
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcPropertyDefinition
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcPropertySetDefinition
DefinesType : SET OF IfcTypeObject FOR HasPropertySets;
IsDefinedBy : SET OF IfcRelDefinesByTemplate FOR RelatedPropertySets;
DefinesOccurrence : SET [0:1] OF IfcRelDefinesByProperties FOR RelatingPropertyDefinition;
ENTITY IfcPropertySet
HasProperties : SET [1:?] OF IfcProperty;


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