Definition

1. A <Feature Face> FF has the following relationship with its associated <Feature Node> instances, if any exist.

   1.1	At any feature topology level, if FF is associated with any <Feature Node> instance FN, then
   	1.1.1 If FF has an <External Feature Face Ring>, FN shall lie within the boundary of that ring. 1.1.2 For each <Internal Feature Face Ring> of FF, FN shall not lie within the boundary of that ring.
   1.2	At feature topology levels 3 and 4, FF shall be associated to each <Feature Node> that is contained within its boundary.
   1.3	If FF contains no <Feature Node> instance within its boundaries, FF shall have no associated <Feature Node> instances.
   1.4	If a <Feature Node> FN does not lie within the boundary of any <Feature Face>, FN shall have no associated <Feature Face> instances.

2. A <Geometry Face> GF has the following relationship with its associated <Geometry Node> instances, if any exist.

   2.1	At any geometry topology level, if GF is associated with a <Geometry Node> GN, GN shall lie within the boundary of GF's <Geometry Face Ring>.
   2.2	At geometry topology levels 3 and 4, GF shall be associated to each <Geometry Node> that is contained within its boundary.
   2.3	If GF contains no <Geometry Node> instances within its boundaries, GF shall have no associated <Geometry Node> instances.
   2.4	If a <Geometry Node> GN does not lie within the boundary of any <Geometry Face>, GN shall have no associated <Geometry Face> instances.

Rationale

The association between <Feature Node> and <Feature Face> is the topological relationship between a <Feature Face> and a <Feature Node> that is contained within its boundaries, so by definition, if the <Feature Face> has an external boundary, the <Feature Node> shall lie within that boundary. The rationale for the relationship between <Geometry Node> and <Geometry Face> is the same.

Unlike <Geometry Face> instances, a <Feature Face> instance may have inner boundaries, indicating "holes" in the <Feature Face>. Consequently, a <Feature Node> shall be contained within a <Feature Face> but not fall into one of the "holes" if it is to be considered "contained" within that <Feature Face>.

Example

1. Consider a <Feature Face> X that contains a <Feature Node> A, where X is part of the <Feature Topology Hierarchy> of a <Classification Related Features> with SE_FEAT_TOPO_LVL_FOUR. X shall have an association with A in order to be valid.

2. Consider <Feature Face> Y that does not contain any <Feature Node> instances. If Y is mistakenly created with an association to some <Feature Node>, then Y is invalid since the association implies that Y does contain the <Feature Node>.

FAQs

Consider a <Feature Face> with a <Feature Face Ring> FFR. Should the <Feature Node> instances forming the endpoints of the edges of FFR be associated to the <Feature Face>?

No, they should not. The containment relationship expressed by that association is one of "proper" containment; that is, it does not include <Feature Node> instances that lie on the boundary of the <Feature Face>.