Schleife - Topologie | |

Loop | |

Boucle |

NOTE Definition according to ISO/CD 10303-42:1992

A loop is a topological entity constructed from a single vertex, or by stringing together connected (oriented) edges, or linear segments beginning and ending at the same vertex. It is typically used to bound a face lying on a surface. A loop has dimensionality of 0 or 1. The domain of a 0-dimensional loop is a single point. The domain of a 1-dimensional loop is a connected, oriented curve, but need not to be manifold. As the loop is a circle, the location of its beginning/ending point is arbitrary. The domain of the loop includes its bounds, an 0 ≤ Ξ < ∞. A loop is represented by a single vertex, or by an ordered collection of oriented edges, or by an ordered collection of points. A loop is a graph, soMand the graph genusGmay be determined by the graph traversal algorithm. Since^{l}M= 1, the Euler equation (1) reduces in this case to whereVandEare the number of unique vertices and oriented edges in the loop and_{l}Gis the genus of the loop.^{l}

NOTE Entity adapted fromloopdefined in ISO 10303-42.

HISTORY New entity in IFC2x.

Informal Propositions:

- A loop has a finite extent.
- A loop describes a closed (topological) curve with coincident start and end vertices.

# | Attribute | Type | Cardinality | Description | G |
---|---|---|---|---|---|

IfcRepresentationItem | |||||

LayerAssignment | IfcPresentationLayerAssignment @AssignedItems | S[0:1] | Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.
IFC2x3 CHANGE The inverse attribute IFC4 CHANGE The inverse attribute | X | |

StyledByItem | IfcStyledItem @Item | S[0:1] | Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.
IFC2x3 CHANGE The inverse attribute | X | |

IfcTopologicalRepresentationItem | |||||

IfcLoop |

` <xs:element name="IfcLoop" type="ifc:IfcLoop" substitutionGroup="ifc:IfcTopologicalRepresentationItem" nillable="true"/>`

<xs:complexType name="IfcLoop">

<xs:complexContent>

<xs:extension base="ifc:IfcTopologicalRepresentationItem"/>

</xs:complexContent>

</xs:complexType>

```
ENTITY IfcLoop
```

SUPERTYPE OF(ONEOF(IfcEdgeLoop, IfcPolyLoop, IfcVertexLoop))

SUBTYPE OF (IfcTopologicalRepresentationItem)**;**

END_ENTITY;

References: IfcFaceBound