Definition

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

   At any topology level, if a <Feature Edge> FE associates to a <Feature Face> FF, then FF shall have a component <Feature Face Ring> that associates to FE. Conversely, if a <Feature Face> FF has a component <Feature Face Ring> that associates to a <Feature Edge> FE, then FE shall also associate to FF.

2. <Geometry Edge> instances have the following relationship with <Geometry Face> instances. At any topology level, if a <Geometry Edge> GE associates to a <Geometry Face> GF, then GF shall also associate to GE. Conversely, if a <Geometry Face> GF associates to a <Geometry Edge> GE, then GE shall also associate to GF.

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

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

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

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