Definition

1. <Feature Edge> instances have the following relationship with <Feature Face> instances:

   1. At any feature topology level, if a <Feature Edge> instance E associates to a <Feature Face> instance F, F shall have a <Feature Face Ring> component that associates to E.

   2. At feature topology level 3 or higher, if a <Feature Face> instance F has a <Feature Face Ring> component that associates to a <Feature Edge> instance E, E shall associate to F.

2. <Geometry Edge> instances have the following relationship with <Geometry Face> instances.

   1. At any geometry topology level, if a <Geometry Edge> instance E associates to a <Geometry Face> instance F, F shall associate to E.

   2. At geometry topology level 3 or higher, if a <Geometry Face> instance F associates to a <Geometry Edge> instance E, E shall associate to F.

Rationale

The associations between <Feature Edge> and <Feature Face> implement a boundary/co-boundary relationship. This topological relationship must be consistent, and must also be consistent with the geometric representations of these objects.

The associations between <Geometry Edge> and <Geometry Face> implement a boundary/co-boundary relationship. This topological relationship must be consistent, and must also be consistent with the geometric counterparts of these objects.

Example

1. A <Feature Face> instance F1 is bounded by two <Feature Edge> instances E1 and E2. F1 is associated to both E1 and E2. Also, E1 and E2 are both associated to F1.

2. A <Geometry Face> instance F1 is bounded by two <Geometry Edge> instances E1 and E2. F1 is associated to both E1 and E2. Also, E1 and E2 are both associated to F1.

FAQs

Can a <Feature Edge> instance be associated with a <Feature Face> instance more than once?

Yes. A <Feature Edge> instance that "dangles" into the interior of a <Feature Face> instance F will appear twice in the collection of <Feature Edge> instances that are associated with the exterior <Feature Face Ring> component of F, once with each orientation. A <Feature Edge> instance that "floats" within the interior of a <Feature Face> instance F will appear twice in the collection of <Feature Edge> instances that are associated with an interior <Feature Face Ring> component of F, once with each orientation.

Can a <Geometry Edge> instance be associated with a <Geometry Face> instance more than once?

Yes. A <Geometry Edge> instance that "dangles" into the interior of a <Geometry Face> instance F will appear twice in the collection of <Geometry Edge> instances that are associated with F, once with each orientation.