Class Name: Face Direction

Superclass - <SEDRIS Abstract Base>

Subclasses

Definition

An instance of this DRM class specifies, for the associated relationship, whether the front or back of the target face is associated with the surface being described.

Primary Page in DRM Diagram:

• 12

Secondary Pages in DRM Diagram:

• 8
• 13

Example

1. Consider an <Areal Feature> instance representing a grass-covered region, consisting of a single <Feature Face> instance. The <Face Direction> link object on the relationship between them is set to SE_TRUE, indicating that the front (that is, the top) side of the face corresponds to the <Areal Feature> instance.

2. Consider a <Polyhedron> instance specifying a room within a building and a <Geometry Volume> instance representing the topological connectivity of the boundary of the room. The <Polygon> instance representing a wall of the room that is an interior wall of the building has a <Geometry Face> instance associated to the <Polyhedron> instance through a <Face Direction> link object with front field = SE_FALSE.

   A second <Polyhedron> instance representing a room on the other side of the same wall has a <Geometry Volume> instance associated to the same <Polygon> instance, but through a <Face Direction> link object with front = SE_TRUE.

FAQs

What if both sides of a <Feature Face> instance are associated with the same <Areal Feature> instance?

In such a case the <Feature Face> instance appears twice in the collection of <Feature Face> components of the <Areal Feature> instance, once with the front field of the corresponding <Face Direction> link object set to SE_TRUE, and once with the front field of the corresponding <Face Direction> link object set to SE_FALSE.

What if the two sides of a <Feature Face> instance are associated with different <Areal Feature> instances?

In such a case the <Feature Face> instance appears once in the collection of <Feature Face> components of each of the two <Areal Feature> instances. For the <Areal Feature> instance corresponding to the front side of the face, the corresponding <Face Direction> link object has front set to SE_TRUE, while for the <Areal Feature> instance corresponding to the back side of the <Feature Face> instance, the <Face Direction> link object has front set to SE_FALSE.

What constraints does feature topology level place upon <Face Direction> link objects?

See <<Face Direction Levels 0 3>>.

Constraints

• <<Publishable Object>>
• <<Face Direction Levels 0 3>>

Inherited Field Elements

Field Elements

Notes

Fields Notes

front

If the value of the front field is SE_TRUE, the front face is associated with the given DRM object. Otherwise, it is the back face that is associated.