IfcPath

注：定义根据ISO/CD 10303-42:1992

路径是一种拓扑实体，由有序的有向边集合组成，使得每条边的边起始点与其前一条边的边结束点重合。路径是从第一条定向边的边起点到最后一条边的边末端的顺序。定向边中的布尔值意义表示边方向与路径方向一致（TRUE）还是相反方向（FALSE）。

单个边只能由单个路径引用一次。一条边可以被多条路径引用。边可以独立于路径存在。

注：实体改编自ISO 10303-42中定义的路径。

IFC2.0中增加的新实体

非正式提议：

①路径的维数为1。

②路径是弧连接的。

③除了在公共顶点处，路径的边不相交。

④路径有一个有限的、非零的范围。

Formal Propositions

Rule	Description
IsContinuous	The end vertex of each edge shall be the same as the start vertex of its successor.

 

#	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
IfcPath
1	EdgeList	IfcOrientedEdge	~L[1:?]	The list of oriented edges which are concatenated together to form this path.	X

 

EXPRESS Specification

ENTITY IfcPath
 SUBTYPE OF (IfcTopologicalRepresentationItem);
  EdgeList : LIST [1:?] OF UNIQUE IfcOrientedEdge;
 WHERE
  IsContinuous : IfcPathHeadToTail(SELF);
END_ENTITY;