IfcTopologyRepresentation

BACnet MVD

#### IfcTopologyRepresentation

Natural language names

| Topologische Repräsentation
| Topology Representation
| Représentation topologique

##### Semantic definitions at the entity

Entity definition

IfcTopologyRepresentation represents the concept of a particular topological representation of a product or a product component within a representation context. This representation context does not need to be (but may be) a geometric representation context. Several representation types for shape representation are included as predefined types:

Vertex | topological vertex representation (with or without assigned geometry)
Edge | topological edge representation (with or without assigned geometry)
Path | topological path representation (with or without assigned geometry)
Face | topological face representation (with or without assigned geometry)
Shell | topological shell representation (with or without assigned geometry)
Undefined | no constraints imposed

The representation type is given as a string value at the inherited attribute 'RepresentationType'.

> HISTORY New entity in IFC2x2.

Formal Propositions

Rule | Description
--- | ---
WR21 | Only topological representation items should be used.
WR22 | A representation type should be given to the topology representation.
WR23 | Checks the proper use of Items according to the RepresentationType.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcRepresentation
1 | ContextOfItems | IfcRepresentationContext |  | Definition of the representation context for which the different subtypes of representation are valid. | X | X
2 | RepresentationIdentifier | IfcLabel | ? | The optional identifier of the representation as used within a project. | X | X

3

RepresentationType

IfcLabel

?

The description of the type of a representation context. The representation type defines the type of geometry or topology used for representing the product representation. More information is given at the subtypes IfcShapeRepresentation and IfcTopologyRepresentation.
The supported values for context type are to be specified by implementers agreements.

X

X

4 | Items | IfcRepresentationItem | S[1:?] | Set of geometric representation items that are defined for this representation. | X | X

RepresentationMap

IfcRepresentationMap
@MappedRepresentation

S[0:1]

Use of the representation within an IfcRepresentationMap. If used, this IfcRepresentation may be assigned to many representations as one of its Items using an IfcMappedItem. Using IfcRepresentationMap is the way to share one representation (often of type IfcShapeRepresentation) by many products.

> IFC2x3 CHANGE The inverse attribute LayerAssignments has been added

X

LayerAssignments

IfcPresentationLayerAssignment
@AssignedItems

S[0:?]

Assignment of the whole representation to a single or multiple layer(s). The LayerAssigments can be overridden by LayerAssigments of the IfcRepresentationItem's within the list of Items.

> NOTE Implementation agreements can restrict the maximum number of layer assignments to 1.

> IFC2x3 CHANGE The inverse attribute LayerAssignments has been added

X

OfProductRepresentation

IfcProductRepresentation
@Representations

S[0:?]

Reference to the product representations to which this individual representation applies. In most cases it is the reference to one or many product shapes, to which this shape representation is applicable.

> IFC4 CHANGE Inverse relationship cardinality relaxed to be 0:N.

X

IfcShapeModel
| OfShapeAspect | IfcShapeAspect @ShapeRepresentations | S[0:1] | Reference to the shape aspect, for which it is the shape representation. |  | X
IfcTopologyRepresentation

##### Formal representations

XML Specification
`<xs:element name="IfcTopologyRepresentation" type="ifc:IfcTopologyRepresentation" substitutionGroup="ifc:IfcShapeModel" nillable="true"/>
<xs:complexType name="IfcTopologyRepresentation">
<xs:complexContent>
<xs:extension base="ifc:IfcShapeModel"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcTopologyRepresentation
SUBTYPE OF (IfcShapeModel);
WHERE
WR21 : SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items |
NOT('IFCTOPOLOGYRESOURCE.IfcTopologicalRepresentationItem' IN TYPEOF(temp))
)) = 0
;
WR22 : EXISTS(SELF\IfcRepresentation.RepresentationType);
WR23 : IfcTopologyRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);
END_ENTITY;

EXPRESS-G diagram

`

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