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;
原文：https://www.cnblogs.com/herd/p/14094127.html