IfcObject

IfcObject

Defintion from IAI: An IfcObject is the generalization of any semantically treated thing or process. Objects are things as they appear - i.e. occurences.

NOTE Examples of IfcObject include physically tangible items, such as wall, beam or covering, physically existing items, such as spaces, or conceptual items, such as grids or virtual boundaries. It also stands for processes, such as work tasks, for controls, such as cost items, for actors, such as persons involved in the design process, etc.

Objects can be named, using the inherited Name attribute, the should be a user recognizable label for the object occurrance. Further explanations to the object can be given using the inherited Description attribute. The ObjectType attribute is used:

to store the user defined value for all subtypes of IfcObject, where a PredefinedType attribute is given, and its value is set to USERDEFINED.
to provide a type information (could be seen as a very lightweight classifier) of the subtype of IfcObject, if no PredefinedType attribute is given. This is often the case, if no comprehensive list of predefined types is available.

Objects are independent pieces of information that might contain or reference other pieces of information. There are four essential kind of relationships in which objects can be involved:

Assignment of other objects - an assignment relationship (IfcRelAssigns) refers to other types of objects and creates a bi-directional association. The semantic of the assignment is established at the level of the subtypes of the general IfcRelAssigns relationship. There is no dependency implied a priori by the assignment.
Association to external resources - an association relationship (IfcRelAssociates) refer to external sources of information (most notably a classification or document) and creates a uni-directional association. There is no dependency implied by the association.
Aggregation of other objects - an aggregation relationship (IfcRelDecomposes) that establishes a whole/part relation and creates a bi-directional relation. There is an implied dependency established.
Refinement by type and properties - a refinement relationship (IfcRelDefines) that uses a type definition or (partial) property set definition to define the properties of the object instance. It is a specific - occurrence relationship with implied dependencies (as the occurrence properties depend on the specific properties).

HISTORY New Entity in IFC Release 1.0

EXPRESS specification:

ENTITY IfcObject

ABSTRACT SUPERTYPE OF

(ONEOF(IfcActor, IfcControl, IfcGroup, IfcProcess, IfcProduct, IfcProject, IfcResource))

SUBTYPE OF (

IfcRoot);

ObjectType

OPTIONAL IfcLabel;

INVERSE

IsDefinedBy

SET OF IfcRelDefines FOR RelatedObjects;

HasAssociations

SET OF IfcRelAssociates FOR RelatedObjects;

HasAssignments

SET OF IfcRelAssigns FOR RelatedObjects;

Decomposes

SET [0:1] OF IfcRelDecomposes FOR RelatedObjects;

IsDecomposedBy

SET OF IfcRelDecomposes FOR RelatingObject;

WHERE

WR1

SIZEOF(QUERY(temp <* IsDefinedBy | 'IFCKERNEL.IFCRELDEFINESBYTYPE' IN TYPEOF(temp))) <= 1;

END_ENTITY;

Attribute definitions:

ObjectType	:	The type denotes a particular type that indicates the object futher. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute 'PredefinedType' is set to USERDEFINED.
IsDefinedBy	:	Set of Relationships to type or property (statically or dynamically defined) information that further define the object. In case of type information, the associated IfcObjectType contains the specific information (or type, or style), that is common to all instances of IfcObject refering to the same type.
HasAssociations	:	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.
HasAssignments	:	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.
Decomposes	:	References to the decomposition relationship, that allows this object to be a part of the decomposition. An object can only be part of a single decomposition (to allow hierarchical strutures only).
IsDecomposedBy	:	Reference to the decomposition relationship, that allows this object to be the composition of other objects. An object can be decomposed by several other objects.

Formal Propositions:

WR1

Only maximum of one relationship to an underlying type (by an IfcRelDefinesByType relationship) should be given for an object instance.

Inheritance graph

ENTITY IfcObject;

ENTITY IfcRoot;

GlobalId

IfcGloballyUniqueId;

OwnerHistory

IfcOwnerHistory;

Name

OPTIONAL IfcLabel;

Description

OPTIONAL IfcText;

ENTITY IfcObject;

ObjectType

OPTIONAL IfcLabel;

INVERSE

IsDefinedBy

SET OF IfcRelDefines FOR RelatedObjects;

HasAssociations

SET OF IfcRelAssociates FOR RelatedObjects;

HasAssignments

SET OF IfcRelAssigns FOR RelatedObjects;

Decomposes

SET [0:1] OF IfcRelDecomposes FOR RelatedObjects;

IsDecomposedBy

SET OF IfcRelDecomposes FOR RelatingObject;

END_ENTITY;