5.1.3.3 IfcContext

Contexte
Kontextinformation

IfcContext is the generalization of a project context in which objects, type objects, property sets, and properties are defined. The IfcProject as subtype of IfcContext provides the context for all information on a construction project, it may include one or several IfcProjectLibrary's as subtype of IfcContext to register the included libraries for the project. A library of products that is referenced is declared within the IfcProjectLibrary as the context of that library.

Context definitions can be named, using the inherited Name attribute, which should be a user recognizable key or number for the context. The LongName can add a full name. Further explanations to the context can be given using the inherited Description attribute.

A Context is declared by the relationship object IfcRelDeclares that refers to the corresponding objects within the context. More specific relationships are introduced at the level of subtypes.

HISTORY  New abstract entity in IFC4.

XSD Specification:

 <xs:element name="IfcContext" type="ifc:IfcContext" abstract="true" substitutionGroup="ifc:IfcObjectDefinition" nillable="true"/>
 <xs:complexType name="IfcContext" abstract="true">
  <xs:complexContent>
   <xs:extension base="ifc:IfcObjectDefinition">
    <xs:sequence>
     <xs:element name="RepresentationContexts" nillable="true" minOccurs="0">
      <xs:complexType>
       <xs:sequence>
        <xs:element ref="ifc:IfcRepresentationContext" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcRepresentationContext"/>
       <xs:attribute ref="ifc:cType" fixed="set"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
      </xs:complexType>
     </xs:element>
     <xs:element name="UnitsInContext" type="ifc:IfcUnitAssignment" nillable="true" minOccurs="0"/>
    </xs:sequence>
    <xs:attribute name="ObjectType" type="ifc:IfcLabel" use="optional"/>
    <xs:attribute name="LongName" type="ifc:IfcLabel" use="optional"/>
    <xs:attribute name="Phase" type="ifc:IfcLabel" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>

EXPRESS Specification:

ENTITY IfcContext
ABSTRACT SUPERTYPE OF(ONEOF(IfcProject, IfcProjectLibrary))
SUBTYPE OF IfcObjectDefinition;
ObjectType : OPTIONAL IfcLabel;
LongName : OPTIONAL IfcLabel;
Phase : OPTIONAL IfcLabel;
RepresentationContexts : OPTIONAL SET [1:?] OF IfcRepresentationContext;
UnitsInContext : OPTIONAL IfcUnitAssignment;
INVERSE
IsDefinedBy : SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects;
Declares : SET OF IfcRelDeclares FOR RelatingContext;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

ObjectType : The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes.
LongName : Long name for the context as used for reference purposes.
Phase : Current project phase, or life-cycle phase of this project. Applicable values have to be agreed upon by view definitions or implementer agreements.
RepresentationContexts : Context of the representations used within the context. When the context is a project and it includes shape representations for its components, one or several geometric representation contexts need to be included that define e.g. the world coordinate system, the coordinate space dimensions, and/or the precision factor.
IFC4 CHANGE  The attribute has been changed to be optional. Change made with upward compatibility for file based exchange.
UnitsInContext : Units globally assigned to measure types used within the context.
IFC4 CHANGE  The attribute has been changed to be optional. Change made with upward compatibility for file based exchange.
IsDefinedBy : Set of relationships to property set definitions attached to this context. Those statically or dynamically defined properties contain alphanumeric information content that further defines the context.
IFC4 CHANGE  The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.
Declares : Reference to the IfcRelDeclares relationship that assigns the uppermost entities of includes hierarchies to this context instance.
NOTE  The spatial hiearchy is assigned to IfcProject using the IfcRelAggregates relationship. This is a single exception due to compatibility reasons with earlier releases.

Inheritance Graph:

ENTITY IfcContext
ENTITY IfcRoot
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
INVERSE
HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy : SET OF IfcRelNests FOR RelatingObject;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcContext
ObjectType : OPTIONAL IfcLabel;
LongName : OPTIONAL IfcLabel;
Phase : OPTIONAL IfcLabel;
RepresentationContexts : OPTIONAL SET [1:?] OF IfcRepresentationContext;
UnitsInContext : OPTIONAL IfcUnitAssignment;
INVERSE
IsDefinedBy : SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects;
Declares : SET OF IfcRelDeclares FOR RelatingContext;
END_ENTITY;

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