IFC 4.3.x development

5.1.3.3 IfcContext

Change log

IFC4

added

5.1.3.3.1 Semantic definitions at the entity

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.

5.1.3.3.1 Attributes

# Attribute Type Description
IfcRoot
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,

> NOTE  only the last modification in stored - either as addition, deletion or modification.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
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.
IfcObjectDefinition
HasAssignments SET [0:?] OF IfcRelAssigns FOR RelatedObjects Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.
Nests SET [0:1] OF IfcRelNests FOR RelatedObjects References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical strutures only).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
IsNestedBy SET [0:?] OF IfcRelNests FOR RelatingObject References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
HasContext SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object.

> IFC4 CHANGE  The inverse attribute datatype has been added.
IsDecomposedBy SET [0:?] OF IfcRelAggregates FOR RelatingObject References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definitions can be aggregated by several other objects (occurrences or parts).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
Decomposes SET [0:1] OF IfcRelAggregates FOR RelatedObjects References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definitions can only be part of a single decomposition (to allow hierarchical strutures only).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification.
IfcContext
5 ObjectType OPTIONAL IfcLabel The object type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes.

> NOTE  Subtypes of IfcContext do not introduce a PredefinedType attribute, therefore the usage of ObjectType is not bound to the selection of USERDEFINED within the PredefinedType enumaration.
6 LongName OPTIONAL IfcLabel Long name for the context as used for reference purposes.
7 Phase OPTIONAL IfcLabel Current project phase, or life-cycle phase of this project. Applicable values have to be agreed upon by view definitions or implementer agreements.
8 RepresentationContextsOPTIONAL SET [1:?] OF IfcRepresentationContext 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.
9 UnitsInContext OPTIONAL IfcUnitAssignment 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 [0:?] OF IfcRelDefinesByProperties FOR RelatedObjectsSet 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 SET [0:?] OF IfcRelDeclares FOR RelatingContext 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.

5.1.3.3.2 Entity inheritance

dot_inheritance IfcProject IfcProject IfcContext IfcContext IfcProject->IfcContext IfcObjectDefinition IfcObjectDefinition IfcContext->IfcObjectDefinition IfcProjectLibrary IfcProjectLibrary IfcProjectLibrary->IfcContext IfcObject IfcObject IfcObject->IfcObjectDefinition IfcRoot IfcRoot IfcObjectDefinition->IfcRoot IfcTypeObject IfcTypeObject IfcTypeObject->IfcObjectDefinition IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot IfcRelationship IfcRelationship IfcRelationship->IfcRoot

5.1.3.3.3 Definitions applying to General Usage

5.1.3.3.3.1 Classification Association

Any object occurrence or object type can have a reference to a specific classification reference, i.e. to a particular facet within a classification system.

5.1.3.3.3.2 Identity

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

5.1.3.3.3.3 Revision Control

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

5.1.3.3.4 Formal representations

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 [0:?] OF IfcRelDeclares FOR RelatingContext;
END_ENTITY;