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	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 LayerAssignments has been added. IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.	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 StyledByItem has been added.	X
IfcTopologicalRepresentationItem
IfcLoop

Formal representations

XML 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