5.1.3.7 IfcObjectDefinition
ABSTRACT This definition may not be instantiated
5.1.3.7.1 Semantic definition
An IfcObjectDefinition is the generalization of any semantically treated thing or process, either being a type or an occurrence. Object definitions can be named, using the inherited Name attribute, which should be a user recognizable label for the object occurrence. Further explanations to the object can be given using the inherited Description attribute. A context is a specific kind of object definition as it provides the project or library context in which object types and object occurrences are defined.
Objects are independent pieces of information that might contain or reference other pieces of information. There are five essential kinds of relationships in which object definitions (by their instantiable subtypes) can be involved:
- Assignment of other objects - an assignment relationship (IfcRelAssigns) that 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) that refers 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 (IfcRelAggregates) that establishes an unordered, spatial whole/part relation and creates a bi-directional relation. There is an implied dependency established.
- Nesting of other objects - a nesting relationship (IfcRelNests) that establishes an ordered, non-spatial whole/part relation and creates a bi-directional relation. There is an implied dependency established.
- Declaration within a context - a relationship (IfcRelDeclares) of the uppermost object definition within the object definition tree (e.g. the summary object within an object nesting tree) to the context (a project or project library). It applies the units, representation context and other context information to this object definition and all dependent ones.
5.1.3.7.2 Entity inheritance
5.1.3.7.3 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, Only the last modification is stored - either as addition, deletion or modification. 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. |
| Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes | |||
| IfcObjectDefinition (7) | |||
| 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 structures only). 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). 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. 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 definition can be aggregated by several other objects (occurrences or parts). The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates. |
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| 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 definition can only be part of a single decomposition (to allow hierarchical structures only). The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates. |
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| 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. |
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5.1.3.7.4 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. |
|
| Click to show 2 hidden inherited concepts Click to hide 2 inherited concepts | |||
| IfcObjectDefinition (9) | |||
| Classification Association | General |
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. |
|
| Aggregation | General |
No description available. |
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| Approval Association | General |
No description available. |
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| Constraint Association | General |
No description available. |
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| Document Association | General |
No description available. |
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| Library Association | General |
No description available. |
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| Material Association | General |
No description available. |
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| Material Single | General |
No description available. |
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| Nesting | General |
No description available. |
|
5.1.3.7.5 Formal representation
ENTITY IfcObjectDefinition
ABSTRACT SUPERTYPE OF (ONEOF
(IfcContext
,IfcObject
,IfcTypeObject))
SUBTYPE OF (IfcRoot);
INVERSE
HasAssignments : SET [0:?] OF IfcRelAssigns FOR RelatedObjects;
Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy : SET [0:?] OF IfcRelNests FOR RelatingObject;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET [0:?] OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET [0:?] OF IfcRelAssociates FOR RelatedObjects;
END_ENTITY;