IfcLoop

Semantic definitions at the entity

Entity definition

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, so M and the graph genus G^l may be determined by the graph traversal algorithm. Since M = 1, the Euler equation (1) reduces in this case to
where V and E_l are the number of unique vertices and oriented edges in the loop and G^l is the genus of the loop.

NOTE Entity adapted from loop defined 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.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
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.	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.	X
IfcTopologicalRepresentationItem
IfcLoop

Formal representations

XSD Specification

 <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>

EXPRESS Specification


ENTITY IfcLoop

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

 SUBTYPE OF (IfcTopologicalRepresentationItem);

END_ENTITY;

 EXPRESS-G diagram

	Schleife - Topologie
	Loop
	Boucle