Definition

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

   1.1	At any feature topology level, if FF is associated with any <Feature Node> FN, then
   	1.1.1 If FF has an <External Feature Face Ring>, then all of its associated <Feature Nodes> shall lie within the boundary of that ring. Otherwise, FF is a <Universal Feature Face> and has no outer boundary. 1.1.2 If FF has <Internal Feature Face Rings>, then none of its associated <Feature Nodes> shall lie within the boundary of any of those rings, which mark its inner boundaries.
   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 Nodes> within its boundaries, it shall not have any associated <Feature Nodes>.
   1.4	If a <Feature Node> does not lie within the boundary of any <Feature Face>, then it shall not have any associated <Feature Faces>.




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

   2.1	At any geometry topology level, if GF is associated with any <Geometry Node> GN, then all of its associated <Geometry Nodes> shall lie within the boundary of its <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 Nodes> within its boundaries, it shall not have any associated <Geometry Nodes>.
   2.4	If a <Geometry Node> does not lie within the boundary of any <Geometry Face>, then it shall not have any associated <Geometry Faces>.

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 Faces>, <Feature Faces> may have inner boundaries, indicating "holes" in the <Feature Face>. Consequently, a <Feature Node> shall be contained within the <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 Nodes>. 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 Nodes> 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 Nodes> that lie on the boundary of the <Feature Face>.